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The present work aims to evaluate the performance of a novel three-phase reactor Belt Conveyor Reactor BCR (with rotating sieve trays patent GB2567340B) as a photobioreactor compared with a traditional Airlift Bubble Column ALR, both influenced by the flow of the gas. Chlorella vulgaris was cultivated in these two photobioreactors using ambient air has a CO 2 concentration of 0.038% with different aeration flowrates 0.145, 0.195, 0.24, and 0.29 vvm (gas volume per minute/liquid volume in the reactor). The maximum growth rate achieved on the 14th day of culture was 2.120 and 1.420 g/L for BCR, ALR respectively, with initial biomass concentrations of 0.2 g/L and aeration flow of 0.29 vvm. Moreover, the removal efficiency of carbon dioxide sequestration by the two photobioreactors is 40% for BCR and 25% for ALR. The innovative design succeeded in operational quality of agitation with high gas holdup inside the sieve trays to increase the biomass growth up to 50% higher than in the ALR. The maximum CO 2 fixation for ALR was at about 18% at a specific aeration rate of 0.145 vvm in the bubbly regime. Whereas in the BCR can be reached about 38% with wide range operation condition of airflow rate 0.145–0.24 vvm due to well-distributed liquid due to rotating trays, and good gas–liquid mass transfer surface area. [ABSTRACT FROM AUTHOR]

• Assessing the effect of prebiotic on Lactobacillus casei. • Combining Spirulina platensis and L. casei. • Using molecular studies to confirm the mixture efficacy. • The present work elucidated the magnificent role of Spirulina as an immunomodulatory agent through being a prebiotic agent to mediate the antibacterial responses of L. casei. Microalgae are diminutive unicellular magnificent creatures that exist in the microscopic form. Within this classification, two notable subtypes, namely Spirulina platensis and Chlorella vulgaris , have garnered significant attention. S. platensis is mostly known for its therapeutic benefits due to proteins, vitamins, essential amino acids, minerals, and essential fatty acids abundance. The subsequent work aimed to investigate the prebiotic effect of S. platensis enhancing Lactobacillus casei microbiome growth rate and antibacterial effect. Different concentrations of S. platensis were prepared (0, 0.5, 5, and 50 mg/mL) then co-cultured with L. casei. Live probiotic enumeration, molecular characterization and scanning electron microscopy studies were performed. Data revealed that 5 mg/mL of S. platensis significantly enhanced the probiotic live count and consequently the antibacterial activity. The antibacterial and antibiofilm effects of L. casei / S. platensis mixture showed complete inhibition to the growth of bacterial cells after 4- and 8-h incubation with Staphylococcus epidermidis 12228 and Escherichia coli 25922, respectively. Moreover, minimal biofilm eradication concentration (MBEC) value of 16 µg/mL was recorded for L. casei / S. platensis mixture [ABSTRACT FROM AUTHOR]

The present work aims to investigate the cumulative effect of hydrogen enrichment with the fuels of diesel, Neat chlorella vulgaris oil (NCVO), and Chlorella vulgaris methyl ester (CVME) in a mono-cylinder CI engine. The performance, combustion, and emission parameters of diesel, NCVO, and CVME are analyzed and compared to the findings obtained with hydrogen induction in the intake manifold under dual fuel configuration. With the effect of hydrogen infusion, the metrics of performance, combustion and emission parameters are improved. Under maximum load condition, the induction of hydrogen escalates the BTE from 32.74%, 28.01%, and 23.02%–35.39%, 31.40%, and 28.12% with diesel, CVME, and NCVO at maximal hydrogen share energy of 14.38%, 11.50% and 9.61% respectively. Alongside, the enrichment of hydrogen declines the carbon monoxide (CO) from 4.13, 10.38, and 19.24 g/kWh to 3.16, 8.02, and 15.26 g/kWh, unburned hydrocarbons (UHC) from 0.51, 0.71, and 2.02 g/kWh to 0.36, 0.50, and 1.64 g/kWh, smoke opacity from 55%, 75%, and 85%–43%, 67%, and 71% with diesel, CVME, and NCVO respectively. However, the hydrogen's significant flame velocity and immense calorific value confect to an elevated combustion temperature and subsequent rise in heat release rate (HRR) to, cylinder pressure, and emission of nitrogen oxide (NO). Among the tested fuels, diesel posses maximum HRR and cylinder pressure of 80.46 J/0CA and 88.67 bar respectively. Maximum specific NO emission was observed with CVME having 10.80 g/kWh, whereas diesel and NCVO has 9.49 g/kWh and 4.93 g/kWh respectively. • Explored fuel characterization studies of chlorella vulgaris methyl ester. • Poorer combustion and performance with neat chlorella vulgaris oil. • Using chlorella vulgaris methyl ester in compression ignition engine. • Hydrogen induction improves performance and reduces emissions with all tested fuels. [ABSTRACT FROM AUTHOR]

Bioremediation became a promising technology to resolve arsenic (As) contamination in aquatic environment. Since monoculture such as microalgae or bacteria was sensitive to environmental disturbance and vulnerable to contamination, green microalgae Chlorella vulgaris and arsenite (As(III)) - oxidizing bacteria Pseudomonas sp. SMS11 were co-cultured to construct algal-bacterial consortia in the current study. The effects of algae-bacteria (A:B) ratio and exposure As(III) concentration on algal growth, As speciation and metabolomic profile were investigated. Algal growth arrested when treated with 100 mg/L As(III) without the co-cultured bacteria. By contrast, co-cultured with strain SMS11 significantly enhanced As tolerance in C. vulgaris especially with A:B ratio of 1:10. All the As(III) in culture media of the consortia were oxidized into As(V) on day 7. Methylation of As was observed on day 14. Over 1% and 0.5% of total As were converted into dimethylarsinic acid (DMA) after 21 days cultivation when the initial concentrations of As(III) were 1 and 10 mg/L, respectively. Metabolomic analysis was further performed to reveal the response of consortia metabolites to external As(III). The enriched metabolomic pathways were associated with carbohydrate, amino acid and energy metabolisms. Tricarboxylic acid cycle and glyoxylate and dicarboxylate metabolism were upregulated under As stress due to their biological functions on alleviating oxidative stress and protecting cells. Both carbohydrate and amino acid metabolisms provided precursors and potential substrates for energy production and cell protection under abiotic stress. Alterations of the pathways relevant to carbohydrate or amino acid metabolism were triggered by energy requirement. [Display omitted] [ABSTRACT FROM AUTHOR]

Biohydrogen (H 2) production by green algae has great biotechnological potential. This study aimed to analyze photosynthetic pigment levels, photosynthetic systems activity, total phenolic/flavonoid content, and H 2 generation in Chlorella vulgaris IBCE C-19 and Parachlorella kessleri MDC6524 in response to sulfur (S) and nitrogen (N) deprivation. The results showed that S and N deficiency caused a growth rate decrease in both cultures that was accompanied by a decrease in the photosynthetic pigments levels, PS II activity, and polyphenols synthesis. In addition, S and N deprivation led to an increase in the H 2 generation. Moreover, the H 2 photoproduction by P. kessleri was higher compared to that of C. vulgaris under N- and S-deprived anaerobic conditions. DCMU inhibited the H 2 production by both algae showing the involvement of PS II in this process. The findings contribute to the ongoing research on the development of strategies to optimize algae cultivation for enhanced H 2 yield. • N and S deprivation leads to a decrease in pigments content and PS II activity. • N and S starvation increases H 2 generation in Parachlorella and Chlorella cultures. • P. kessleri produce more H 2 than C. vulgaris under N- and S-deprived conditions. • DCMU inhibited H 2 production by green algae under N- and S-deprived conditions. [ABSTRACT FROM AUTHOR]

Biohydrogen production is influenced by various parameters such as production formation rate, substrates degradation, and biomass utilization. Therefore, it is crucial to predict the kinetics of proper yield. This study was designed to perform a comprehensive kinetic analysis based on several linear or non-linear models. The experimental data analyzed was different co-culture ratios of microalgae and activated sludge with hexitols (glucose, sorbitol, mannitol) as carbon substrates. Results suggest that modified Gompertz model best predicts biohydrogen potential and acetate production in different co-cultures with high R2 values (>0.977 and > 0.982), respectively. A maximum of 9.8 % energy conversion efficiency is achieved in 10 g/L glucose supplemented co-culture, equivalent to traditional fuels. The linearized Luedeking–Piret model also indicates that biohydrogen production is influenced more by substrate degradation/utilization than microalgal biomass. These tools can be utilized to optimize the operational parameters and access the best fit of experimental data for enhanced yield. [Display omitted] • Excellent data fittings of parameters involved in algal activated sludge co-culture. • Biohydrogen and acetate yield can be best predicted by Modified Gompertz model. • Michaelis–Menten model best described kinetic of substrate degradation/utilization. • Relationship of products, substrate, and biomass predicted by Luedeking–Piret model. • Maximum energy conversion efficiency (9.8 %) was achieved in 1:1.5 co-culture ratio. [ABSTRACT FROM AUTHOR]

The technology for obtaining bio hydrogen from the micro algae Chlorella vulgaris is described, the stage of biomass accumulation is intensified, the effect of copper addition on the growth of Chlorella is studied, a new, optimized composition of the Tamiya medium was developed using mathematical modeling, the effect of the light spectrum, carbon dioxide content in the gas-air mixture and Chlorella cultivation was carried out in a continuous mode, which made it possible to greatly accelerate the accumulation of cells. Despite significant achievements in the field of biotechnology, hydrogen accumulation with the help of algae is still economically inexpedient, although the need for research in this direction is associated with the depletion of renewable energy sources, environmental problems and the increase in energy prices. Briefly, the main directions for the competitiveness of the technology are given; one of the vectors for solving this problem is obtaining bio-hydrogen during the metabolism of Chlorella, the cultivation of which is characterized by a number of advantages. The attractiveness of using Chlorella biomass for bio fuels is due to the high rate of biomass reproduction, ease of cultivation, and the use of carbon dioxide and small amounts of mineral salts, agricultural waste or sewage to ensure the growth of Chlorella. Chlorella vulgaris is able to increase the amount of its biomass dozens of times per day, while it takes months or even years for terrestrial plants. [ABSTRACT FROM AUTHOR]

The co-gasification process of Chlorella vulgaris (CV) and petrochemical industrial sludge (IS) was uncoupled and simulated by Aspen Plus. The co-gasification process was considered into drying, pyrolysis, partial oxidation, as well as reduction and reforming. Simulation results showed that, the interactions between IS and CV were found for the differences in CHO, and affected by the IS ratio and gasification temperature. Increasing the temperature could improve the CO content, and get optimal H 2 at 700 °C, while decrease CO 2 and CH 4 contents, thus lead to a higher LHV (lower heating value) of syngas, CGE (cold gas efficiency), and syngas content, CO selection. The higher S/IS-CV (steam to IS-CV blends ratio) value favored H 2 production but reduce CO content and CGE. As air equivalent ratio (ER) increased, the H 2 content constantly reduced, while CO varied slightly when the ER was lower than 0.10. After the ER value was higher than 0.10, CO reduced and thereby decreasing co-gasification performance. When the drying degree of feedstock increased, the CO content continuously increased, leading to better co-gasification performances. The RSM results showed that the significance factors in the interactions are ER and drying degree, S/IS-CV and ER , gasification temperature and ER , and gasification temperature and ER , respectively for CGE , LHV , C syngas , and Sel CO. • Thermodynamic model was used for co-gasification of Chlorella vulgaris and industrial sludge. • Co-gasification process was decoupled into four stages, and integrated optimization. • Co-gasification was affected by conditions of temperature, S/IS-CV, ER, drying degree. • Co-gasification were studied by syngas composition, performance indices, and RSM optimization. [ABSTRACT FROM AUTHOR]

• D. vulgaris induced ferrihydrite transformation via the direct reduction and S2−-driven processes. • The presence of SO 4 2− altered the mineralogical transformation of ferrihydrite. • The formation of magnetite and mackinawite enhanced the stability of As in solids. • High SO 4 2− loadings (SO 4 2−/Fe = 1.5) resulted in the substantial mobilization of As into the solution. Sulfate-reducing bacteria play an important role in the geochemistry of iron (oxyhydr)oxide and arsenic (As) in natural environments; however, the associated reaction processes are yet to be fully understood. In this study, batch experiments coupled with geochemical, spectroscopic, microscopic, and thermodynamic analyses were conducted to investigate the dynamic coupling of ferrihydrite transformation and the associated As desorption/redistribution mediated by Desulfovibrio vulgaris (D. vulgaris). The results indicated that D. vulgaris could induce ferrihydrite transformation via S2−-driven and direct reduction processes. In the absence of SO 4 2−, D. vulgaris directly reduced ferrihydrite, and As desorption and re-sorption occurred simultaneously during the partial transformation of ferrihydrite to magnetite. The increase in SO 4 2− loading promoted the S2−-driven reduction of ferrihydrite and accelerated the subsequent mineralogical transformation. In the low and medium SO 4 2− treatments, ferrihydrite was completely transformed to a mixture of magnetite and mackinawite, which increased the fraction of As in the residual phase and stabilized As. In the high SO 4 2− treatment, although the replacement of ferrihydrite by only mackinawite also increased the fraction of As in the residual phase, 22.1% of the total As was released into the solution due to the poor adsorption affinity of As to mackinawite and the conversion of As5+ to As3+. The mechanisms of ferrihydrite reduction, mineralogy transformation, and As mobilization and redistribution mediated by sulfate-reducing bacteria are closely related to the surrounding SO 4 2− loadings. These results advance our understanding of the biogeochemical behavior of Fe, S, and As, and are helpful for the risk assessment and remediation of As contamination. [Display omitted] [ABSTRACT FROM AUTHOR]

Microalgae-based fuel has attracted attention as a green energy source for the transportation sector owing to its high suitability, availability, and rapid growth rate. Furthermore, algae consume carbon dioxide to produce fuel, and indirectly reduce global warming. This study predicts the effects of microalgae biofuel blends assisted by biogas and nanoparticles on diesel engine performance, combustion, and emission characteristics across various engine speeds for the first time. Biogas, which is rich in carbon monoxide and hydrogen, passed through the intake manifold at a constant flow rate of 10 L per minute. Al 2 O 3 nanoparticles were dispersed in the biodiesel at a concentration of 100 ppm. The inclusion of hydrogen enhanced both the brake power and brake thermal efficiency of the engine irrespective of engine speed. A blend of both biogas and nanoparticles resulted in less specific fuel consumption than Chlorella vulgaris biodiesel blends owing to lower viscosity and higher energy ratio. However, the inclusion of nanoparticles reduced the in-cylinder pressure. In terms of emissions, all the microalgae blends exhibited reduced formation of carbon monoxide, carbon dioxide, and hydrocarbon compared to diesel. However, the formation of nitrogen of oxides in 20% microalgae blend A20 was higher than that in diesel and 20% microalgae blend with nanoparticle (AB20 N). Owing to the presence of CO in the biogas, the total accumulation of CO and CO 2 was higher for AB20 N than for other fuel blends. From the above analysis, it is clear that CO can be used in conjunction with hydrogen to assist the internal combustion process. [Display omitted] • A blend of both hydrogen, biogas and nanoparticles added to diesel fuel improved the engine performance. • The addition of nanoparticles resulted in a decrease in the maximum combustion pressures. • The fuel blend used caused the CO, CO2 and HC emission to reduce in the exhaust gasses. • The fuel blend increased the level of NOx in the exhaust gasses. • Having carbon monoxide in the biogas showed better engine performance. [ABSTRACT FROM AUTHOR]

Priming effect (PE) is a key biogeochemical process regulating organic carbon mineralization. However, the impacts of climate change-related factors on PE remain largely unclear in lakes with a large salinity range. The patterns of PE induced by algal (13C-labeled Chlorella vulgaris) and terrestrial grass (13C-labeled Festuca ovina) organic matter (OM) at 8 °C and 18 °C were investigated in lake sediments with a salinity range from 0.7 to 376.3 g L−1. The results showed that the intensities of early (7th day) and late (42nd day) PEs in the studied lake sediments ranged −51.0%–3833.7% and −55.2%–1874.5% of basal respiration, respectively; positive PE predominated over negative PE. Climate-related factors (e.g., salinity, temperature, OM types) exhibited significant influences on the intensity and/or direction of PE. Positive PE was more likely to occur in the sediments of hypersaline lakes than in freshwater/saline lakes, while negative PE showed an inverse trend. PE intensity induced by algal OM was significantly different at 8 °C and 18 °C, but no temperature influence was observed for that induced by grass OM. The effect of temperature increase on PE induced by algal OM was negative and positive in the early and late stages of incubation, respectively. The types of OM (algal OM vs. grass OM) supply significantly (P < 0.05) affected PE intensity except for the late PE intensity at 8 °C. Overall, these results suggest that organic carbon mineralization in lake sediments may be enhanced by positive PEs induced by the increased input of both allochthonous and autochthonous OM, and the autochthonous OM-induced PE is more susceptible to climate warming than that by allochthonous OM. These results help understand the carbon cycle in lakes under global climate change. [ABSTRACT FROM AUTHOR]

To expand space explorations into space settlements, there is a need for the establishment of a sustainable, closed-loop life support system. Systems involving microalgae are promising, as they could simultaneously revitalize air (i.e., CO 2 to O 2 conversion), reclaim water (i.e., nutrient biofixation/recycling), and provide food supplement (i.e., biomass). This would entail microalgal cultivation in human-derived wastes (both gas and liquid), which could provide challenges on system tolerance, particularly on the levels of nutrients in these wastes. In this work, the effect of macronutrient [Carbon (C), Nitrogen (N), and Phosphorus (P)] levels on the phototrophic growth of Chlorella vulgaris UTEX 2714 was investigated using synthetic wastewater. This was done to determine the range of macronutrient levels that are suitable for sustained microalgal growth. The highest biomass concentration was achieved when the microalga was axenically cultivated in 71 mg C/L, 64 mg N/L, and 13 mg P/L. With an equivalent C:N:P mass ratio of 5.5:5:1, this cultivation condition was significantly different from the ideal C:N:P of 41:7:1, suggesting a C-limited growth environment. This was also supported by 99.9% C consumption, while only consuming 56% and 72% of N and P, respectively. These results indicate that during space cultivation, incremental amount of C must be added to the microalgal system to improve the overall C:N:P of the process and to enhance N and P consumption, while ensuring that the C level is below the inhibitory threshold limit. Based on these results, together with human-derived wastes data from the International Space Station, a microalgal photobioreactor configuration was proposed. • Uninhibited growth of C. vulgaris in HCO 3 −, NH 4 +, and H 2 PO 4 − is carbon-limited. • Incremental input of CO 2 could improve the consumption of nitrogen and phosphorus. • The threshold macronutrient levels could be used to estimate bioreactor sizes. [ABSTRACT FROM AUTHOR]

Raceways are widely used as microalgae culture systems due to their low cost, but they are not the best option for biomass yield. Understanding in situ photosynthetic performance can be a first step to increase their biomass productivity. This study aimed at comparing the real time photosynthetic activity in a greenhouse raceway culture (250 L) with discrete measurements under laboratory conditions. We evaluated the photophysiology and biochemical composition of Chlorella fusca culture up to 120 h. In situ photosynthetic activity was continuously monitored and compared to discrete ex situ measurements; biochemical compounds were measured daily. The results showed a final biomass density of 0.45 g L–1 (5 days – 120 h) and an increase of the electron transport rate (ETR) up to 48 h but decreased thereafter. When the relative ETR was estimated considering the absorption coefficient (a) positive correlations of this parameter with photosynthetic capacity, cell density, biomass, biocompounds and antioxidant activity were obtained, whereas no correlation was detected without considering a. In situ photosynthesis monitoring showed higher absolute maximal ETR (10 – 160 μmol m–3s–1) than discrete ex situ measurements. We demonstrated the importance of considering the light absorption coefficient for expressing photosynthetic capacity and showed that C. fusca can produce, in the short-term, bioactive compounds that are correlated to photosynthetic conditions. • RLC is more sensitive to cell physiology information than Fv/Fm. • Calculated rETR considering the absorption coefficient supports culture physiology. • Chlorella fusca , with its biocompounds, is a commercially promising microalga. [ABSTRACT FROM AUTHOR]

Microalgae are the third generation of biomasses that have received lots of attention due to their high energy content and ability to capture carbon dioxide from the air. However, there are some techno-economic challenges for their world commercialization. A variety of fuels can be extracted from microalgae, and in addition to these fuels, algae by-products can be used to commercialize this industry. Various processes will be performed on microalgae to finally desired products can be extracted. In this research, an integrated system has been designed for the simultaneous production of ethanol, methane, and hydrogen from Chlorella vulgaris microalgae. The results showed that after culturing, harvesting, and increasing the concentration of the solution in addition to the main products such as ethanol, methane, and hydrogen, by-products including acetic acid, methyl acetate, ethyl acetate, furfural and etc. can be utilized for commercializing microalgae industry. Also, another purpose of this study is to apply Pinch Analysis to the mentioned system, which will ultimately improve the concentration of microalgae in the photobioreactor. The results of Pinch Analysis show that by increasing the concentrations of microalgae, carbon dioxide, and nutrients in the photobioreactor inlet up to 2.35 gr/l, the desired amount of demands can be met by the new supplies. [Display omitted] • Designing a simultaneous production process of ethanol, methane and hydrogen. • Modifying the production of biofuels and value-added materials from the microalgae. • Doing mass balance analysis, energy balance analysis and mass pinch analysis. [ABSTRACT FROM AUTHOR]

Microalgae have received increasing attention as one of the most promising feedstocks in the development of new healthier food products and different strategies have been attempted to improve their growth. However, the high production costs and low productivities, commonly associated with photoautotrophic growths, are still a big challenge. In this study, a two-step optimization strategy was carried out in order to maximize the biomass production of a Chlorella vulgaris strain used at industrial scale under heterotrophic conditions. From a total of 24 independent variables, which were studied simultaneously, 10 have presented a positive effect over Xmax, while the remaining have shown to be negative. The amount of (NH4)2SO4 (6.3 g L-1), MgSO4-7H2O (0.7 g L-1), and C6Hi2O6 (50% w/v) in the culture medium has revealed to be the only factors with a significant impact on biomass concentration, with optimum values of 25.5, 64.6, and 75 ml.L-1, respectively. The optimized medium resulted in an improvement of the Xmax by 99.6% when compared to the growth medium applied at industrial scale, proving the success of this strategy. Additionally, the carbohydrates production was enhanced by 48.0%. [ABSTRACT FROM AUTHOR]

Acid-casein production generates waste streams that are rich in nitrogen (in the form of protein and nitrate) and phosphate. This makes this type of waste very difficult to treat using conventional techniques resulting in a high amount of operating cost and costly investment. In this research, the application of single culture or consortium of microalgae for uptake of nitrogen and phosphate in the wastewater of an acid-casein factory was investigated. The waste was a 1:1 mixture of nanofiltered whey permeate and dairy processing wastewater. Monocultures of Chlorella vulgaris, Tetradesmus obloquus, Nonnochlropsis ocenica and a consortium of the three microalgae were analyzed. The results showed that the consortium exhibited more efficient nitrogen and phosphate removal compared to the individual species. The consortium was able to rapidly hydrolyse exogenous protein present in the waste medium, removing 88% of protein and breaking down complex protein molecules into simpler compounds (such as nitrate) for assimilation into the biomass. In the first fourteen days of cultivation, the rate of nitrate assimilation by the consortium biomass was lower than that of nitrate formation from protein degradation, leading to a net increase in nitrate concentration in the medium. As protein source was depleted and biomass concentration increased, however, the rate of nitrate assimilation began to exceed that of nitrate formation allowing for net removal of nitrate. The microalgae consortium was shown to successfully bioremediate all nitrates by day 21. It was indicated that Chlorella and Nannochloropsis species were responsible for nitrogen removal in monocultures. Phosphate, on the other hand, was efficiently removed by Tetradesmus. The results indicated that a consortium cultivation of three species of microalgae led to effective elimination of both nitrogen and phosphate. Combined flow-cytometry and microscopy analyses revealed that Chlorella overtook Tetradesmus and Nannochloropsis to emerge as the dominant population in the consortium by the end of the cultivation cycle. It can be concluded that the application of microalgae consortium for simultaneous recovery of nitrogen and phosphate is a promising approach for treating acid-casein wastewater. • Growth of microalgae on whey permeate from acid casein processing were analyzed. • Flowcytometry and microscopic analysis confirmed the successful growth of microalgae. • The use of a consortium culture exhibited efficient nutrient removal approach. • Microalgae depleted phosphate and exhibited proteolytic activity. • Application of microalgae for nutrient recovery from acid casein wastewater is promising. [ABSTRACT FROM AUTHOR]

• The experimental results shown that the variant concentration of iron ions in the medium and the variant pH of the initial algal fluid did different effects on the growth of Chlorella vulgaris. The Chlorella vulgaris can thrive better in the culture fluid with iron ions raising. The initial pH of the algae fluid affects its growth mainly in 1–3 days. Meanwhile, in a weak alkaline environment, such as pH 8.27 is beneficial to the growth of Chlorella vulgaris during the initial developing period. Also we find out in a certain range of alkaline environments such as pH 8 to 9 is the more conducive to its growth. By concluding the results of the research, we can obtain the optimal chlorella aquaculture production cultivation conditions with economic benefits. The use of microalgae as raw materials to produce various new biomass energy in the aquaculture industry has become a key issue in building a friendly ecology. However, maximizing algal growth and profit by regulating iron ion concentration (Fe3+) and acid-base value (pH) remains a major challenge. Therefore, this study utilized Chlorella vulgaris to explore the influence of Fe3+ concentration and initial pH value on algal growth to obtain optimum economic benefits and chemical culture conditions. Using an air-lift columnar photobioreactor for cultivation and a fluorescent lamp as a light source, the experiments were conducted at a light intensity of 3537 Lux at approximately 24 °C. To achieve economically optimal culture conditions, the daily OD 660 value of the Chlorella vulgaris cultures was used to explore the effects of different iron ion concentrations and initial pH values on algae growth and biomass accumulation. Our results demonstrated that different iron ion concentrations and pH conditions of the algal culture rendered different effects on Chlorella vulgaris growth. Overall, the enriched iron-containing medium was more favorable for algae growth. Over time, the medium with higher iron concentration (1.0 g/L) achieved higher OD faster and its accumulated chlorophyll was higher. Moreover, the initial pH of the algae culture medium affected its growth mainly within the first three days. Particularly, a weak alkaline environment (e.g., pH 8.27) benefited Chlorella vulgaris growth during the initial growth period. With the results of this study, our research determined the optimal Chlorella production conditions that maximize economic benefits. [ABSTRACT FROM AUTHOR]

The growing resistance from pathogens against antibiotics has increased the research for new compounds and strategies with antibacterial potential. Lipids from algae are emerging as natural and potent bioactive molecules with interesting results regarding the inactivation of bacteria, viruses, and fungi. The combination of algae lipids with innovative strategies, such as antibacterial photodynamic therapy (aPDT) can enhance their antimicrobial potential. In this work, we aimed to evaluate the antibacterial potential in aPDT of total lipid extracts and polar lipid fractions from the green macroalga, Codium tomentosum , and the green microalga, Chlorella vulgaris on a Gram-positive bacteria Staphylococcus aureus. Total lipid extracts and polar lipid fractions were characterized by LC-MS. The results revealed that the total extracts of algae promote S. aureus inhibition after light irradiation, with a decrease of ca. 6 log 10 (CFU/mL) after 15 min of treatment with both extracts of algae. The polar lipid fractions, composed by phospholipids, glycolipids and betaine lipids, from C. tomentosum and C. vulgaris also revealed antibacterial potential in combination with aPDT, but a decrease of ca. 6 log 10 (CFU/mL) was reached at 60 min of treatment, later than with the total extracts. These results unveil algae lipids as antibacterial compounds in combination with aPDT displaying an alternative from natural origin to tackle pathogen resistance. • Algae total extracts are effective photosensitizers when used with aPDT. • Lipids from C. tomentosum and C. vulgaris reduce the viability of S. aureus in aPDT. • Algae polar lipids are effective photosensitizers when used with aPDT. • Algae polar lipids combined with aPDT can enhance their antimicrobial potential. [ABSTRACT FROM AUTHOR]

Nano-biocatalysts, based on Rhizopus oryzae lipase (ROL) immobilized on 3D superparamagnetic graphene oxide (3DMGO) were prepared in two methods and used for the conversion of Chlorella vulgaris oil to biodiesel. The 3D graphene oxide hydrogel was synthetized using two different cross-linking agents, p-phenylene diamine (PPD) and ethylene diamine tetra acetic acid (EDTA), and then magnetized by insitu co-participation of Fe 3 O 4. A modified BG-11 medium was used for cultivation of this microalgae to increase the total biomass lipid (up to 35 wt%). The kinetics parameters, enzyme loading percentage, thermal stability, and storage stability of ROL, ROL/3DMGO-EDTA, and ROL/3DMGO-PPD were evaluated. The biodiesel production yields in the presence of ROL, ROL/3DMGO-PPD, and ROL/3DMGO-EDTA were 75.04%, 74.25%, and 72.12%, respectively. The reusability tests confirmed that the ROL/3DMGO-EDTA had better performance. Therefore, 3D graphene oxide nanostructures can be introduced as a suitable option for enzyme immobilization in the biodiesel production from microalgae oil. [Display omitted] • Preparation of superparamagnetic 3D graphene oxide (3DMGO) as ROL enzyme support. • Biodiesel production from Chlorella vulgaris oil using ROL/3DMGO nano-biocatalyst. • Evaluation of the crosslinking agent type effect on ROL/3DMGO catalytic performance. • Evaluation of ROL/3DMGO kinetic parameters and its thermal and storage stability. • Biomass lipid content increase using a modified BG-11 for microalgae cultivation. [ABSTRACT FROM AUTHOR]

Photosynthetic microorganisms, specifically cyanobacteria and microalgae, can synthesize a vast array of biologically active molecules, such as lectins, that have great potential for various biotechnological and biomedical applications. However, since the structures of these proteins are not well established, likely due to the presence of intrinsically disordered regions, our ability to better understand their functionality is hampered. We embarked on a study of the carbohydrate recognition domain (CRD), intrinsically disordered regions (IDRs), amino acidic composition, as well as and functional motifs in lectins from cyanobacteria of the genus Arthrospira and microalgae Chlorella and Dunaliella genus using a combination of bioinformatics techniques. This search revealed the presence of five distinctive CRD types differently distributed between the genera. Most CRDs displayed a group-specific distribution, except to C. sorokiniana possessing distinctive CRD probably due to its specific lifestyle. We also found that all CRDs contain short IDRs. Bacterial lectin of Arthrospira prokarionte showed lower intrinsic disorder and proline content when compared to the lectins from the eukaryotic microalgae (Chlorella and Dunaliella). Among the important functions predicted in all lectins were several specific motifs, which directly interacts with proteins involved in the cell-cycle control and which may be used for pharmaceutical purposes. Since the aforementioned properties of each type of lectin were investigated in silico , they need experimental confirmation. The results of our study provide an overview of the distribution of CRD, IDRs, and functional motifs within lectin from the commercially important microalgae. • Cyanobacteria and microalgae lectins are few characterized structurally. • Most of carbohydrate recognition domains seems to be microalgae group-specific. • Lectins from Dunaliella and Chlorella contain higher levels of IDR than Artrhospira. • C. sorokiniana is lectin source with higher number and types of functional motifs. [ABSTRACT FROM AUTHOR]

With the rapid expansion of the maricultural scale, the treatment of mariculture tail water (MTW) has become a focus of marine environmental protection. Meanwhile, as a cost-effective wastewater treatment technology, immobilized algal-bacterial beads (IABB) has received wide attention. The nutrients removal of wastewater by IABB is limited by the stability and strength of the beads during the treatment process. In this study, the fabrication of IABB composing Chlorella vulgaris and activated sludge with different concentration of SA (1.5%, 2.5% and 3.5% w/v) and Ca2+ (2%, 3.5% and 5% w/v) and their application in the treatment of synthetic MTW was primarily investigated. The SA concentration has significant impact on the characteristics of IABB. Specifically, 2.5% of SA resulted in the formation of IABB with the best homogeneity, chemical and mechanical stability. Ca2+ concentration affect the nutrient removal efficiency during MTW treatment. The IABB fabricated under the conditions of 2.5% SA and 2% Ca2+ showed the highest removal efficiency of NH 3 -N, TP and COD within the 48 h of experiment, i.e. 66.7 ± 3.2, 81.0 ± 2.8 and 90.7 ± 1.9%, respectively. Therefore, the application of IABB offers promising prospects for MTW treatment and marine environmental safety. [Display omitted] [ABSTRACT FROM AUTHOR]

Aiming at realizing efficient microalgae-based CO 2 sequestration from coal-fired power plants, this study investigated the interaction between the mass transfer of SO 2 -contained flue gas and microalgae growth. The results indicate that the CO 2 dissolution in microalgae suspension and the growth of Chlorella vulgaris could be hindered by solution acidification and oxidative molecular species produced in the conversion of bisulfite to sulfate. With the SO 2 concentration increased from 0 to 400 ppm, the pH of the culture medium decreased from 7 to 2, and the SO 4 2− concentration reached 1 g L−1, resulting in a decrement of 18.1% in the CO 2 dissolution rate. Moreover, the Chlorella cells could only maintain their growth within the SO 4 2− concentration of 800 mg L−1 accompanied by a decrement of 58% in maximum biomass concentration. The cultivation collapsed under excessive SO 2 (over 400 ppm) as the plasmolysis and chloroplast decomposition occurred which severely inhibited the microalgal photosynthesis. This work provides a guide to cultivating microalgae using real flue gas. [Display omitted] [ABSTRACT FROM AUTHOR]

Microalgae fractionation was investigated combining supercritical carbon dioxide extraction of lipids and pigments and protein extraction from the residues, on Chlorella vulgaris and Nannochloropsis oculata. The results indicated that for N. oculata , chlorophyll (a) is extracted rapidly and selectively apart from Chlorophyll (b), representing 34% and 0.41% in 30 min at 450 bar and 50 °C and up to 43% and 0.48% at 750 bar at the same time and temperature, respectively. The extraction profile of chlorophyll (a) is similar to of neutral lipids. For C. vulgaris , the results emphasized the importance of adding a co-solvent during the supercritical extraction to achieve 30% of chlorophyll (a), while the extraction of other pigments was lower especially for chlorophyll (b) extraction yield reaching 0.1% of its total content. Then for the second time, the extraction of proteins was studied on N. oculata delipidated cake. The results showed that the higher the level of delipidation, the higher the extraction yield, with an increase from 54% for crude cake to 73% for delipidated cake. [Display omitted] • he presence of neutral lipids favors the extraction of pigments by supercritical CO 2. • The addition of ethanol allows the extraction of all lipids and pigments. • The extraction of proteins is improved by delipidation. • Lipid extraction allows extraction of unextracted proteins without delipidation. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the purification of radioactive thorium (Th4+) by Chlorella vulgaris in aquatic environment s. Single-factor experiments and response surface optimization tests identified optimal purification conditions. The purification and metabolic response mechanisms of Chlorella to Th4+ were elucidated using physiological and biochemical analyses, three-dimensional excitation-emission matrix (3D-EEM) analysis, and metabolomic profiling. Increases in the Th4+ concentration caused Chlorella to self-flocculate, significantly improving the Th4+ purification efficiency. Under optimal conditions, the Th4+ purification efficiency for Th4+ in wastewater by Chlorella stabilized between 94.3 % and 98.2 %. Morphological analysis revealed that the purified Th4+ existed mainly in a stable residual state. Chlorella efficiently purified wastewater during treatment by regulating environmental pH, performing redox reactions, and utilizing extracellular polymeric substances (EPS) to interact with Th4+. Metabolomic analysis indicated that Chlorella adapted to the Th4+-contaminated environment and enhanced its purification function by adjusting the synthesis of metabolites, such as carbohydrates, nucleotides, and amino acids. Chlorella demonstrated a remarkable self-flocculation phenomenon and a high-efficiency purification capability for Th4+, offering new possibilities for environmental remediation. Its purification mechanism involves environmental regulation, redox reactions, and complex metabolic adjustments. The results presented here provide theoretical support for environmental remediation using Chlorella. [Display omitted] • Chlorella highly efficient purification of radioactive thorium in water (94.3 %−98.2 %). • Chlorella effectively cleans wastewater by interacting with Th4+ through EPS. • Thorium is in a stable residue state, which is safe and reliable to handle. • Chlorella shows strong Th purification ability by adjusting metabolite synthesis. [ABSTRACT FROM AUTHOR]

Arthrospira (Limnospira) maxima (A. maxima) and Chlorella vulgaris (Ch. vulgaris) are among the approved microalgae and cyanobacteria (MaC) in the food industry that are known to be safe for consumption. However, both organisms are controversial regarding their vitamin B 12 content, due to the possible occurrence of pseudo-cobalamin. Concurrently, their nutrition profiles remain understudied. The main purpose of the present study was to identify their nutrition profiles, focusing mainly on vitamin B 12 , amino acids, and micronutrients under iron-induced hormesis (10 mg/L Fe in treated samples). Our findings indicate a higher B 12 content in A. maxima compared to Ch. vulgaris (both control and treated samples). Using liquid chromatography with tandem mass spectrometry (LC-MS/MS), the cyanocobalamin content was determined as 0.42 ± 0.09 μg/g dried weight (DW) in the A. maxima control and 0.55 ± 0.02 μg/g DW in treated A. maxima , resulting in an insignificant difference. In addition, the iron-enriched medium increased the amount of iron in both tested biomasses (p < 0.01). However, a more pronounced (approximately 100×) boost was observed in Ch. vulgaris , indicating a better absorption capacity (control Ch. vulgaris 0.16 ± 0.01 mg/g Fe, treated Ch. vulgaris 15.40 ± 0.34 mg/g Fe). Additionally, Ch. vulgaris also showed a higher micronutrient content. Using both tested microalgae, meeting the sufficient recommended daily mineral allowance for an adult is possible. By combining biomass from A. maxima and Ch. vulgaris in a ratio of 6:1, we can fulfill the recommended daily allowance of vitamin B 12 and iron by consuming 6 tablets/6 g. Importantly, iron hormesis stimulated amino acid composition in both organisms. The profile of amino acids may suggest these biomasses as promising potential nutrition sources. • The determination of vitamin B 12 in Ch. vulgaris and A. maxima biomass using microbial and LC-MS/MS methods. • The cyanocobalamin and pseudocobalamin in A. maxima were detected and determined. • Presenting the nutrition profile of iron, B 12 , amino acids, polyphenols, flavonoids, and proteins in Ch. vulgaris and A. maxima. [ABSTRACT FROM AUTHOR]

[Display omitted] • The design and characterization of a solid-state hydrogel photobioreactor (hPBR). • Analysis: surface coverage, productivity, cell viability, lipid and pigment content. • Growth rate comparable to flask culture and other solid-state cultivation systems. Solid-state cultivation is a promising technology for algal biomass production, achieving high productivities without the need for dewatering. However, such systems have suffered from high evaporation, and capital costs. Here is described a hydrogel photobioreactor (hPBR) with the aim of reducing water demand in solid-state cultivations. Two designs are described with "Design A" offering better humidity control overgrowth conditions. A biomass productivity of 2.41 g m - 2 d - 1 , and 2.87 g m - 2 d - 1 when using physically crosslinked poly(vinyl alcohol) (pPVA) and chemically crosslinked PVA (cPVA) respectively were achieved with Chlorella vulgaris with a water demand around 0.44 kg g−1 of biomass. Over the 23 days of growth, the lipid content increased from 18.9 % to 56.6 % and 13.8 % to 43.2 % for pPVA and cPVA respectively, and the chlorophyll content decreased by more than 81 %. However, cell viability stayed high at over 98 % and surface coverage analysis showed good coverage of the gel surface. [ABSTRACT FROM AUTHOR]

Microalgal biomass can potentially be valorized for several purposes, targeting either high added-value metabolites or biofuels. In case the cultivation conditions are inappropriate for the production of high-value metabolites, or the produced yields are insufficient for extraction and further valorization, there is the alternative of the anaerobic digestion (AD) process for biogas production. In the current study, Chlorella vulgaris biomass was treated through the process of AD, focusing on the effect of fatty acids (FAs) content (5–30 %) on biomethane production. Mixotrophic and heterotrophic conditions were used to produce biomass samples with different FAs content. The biochemical methane potential (BMP) assays of the biomass samples followed, targeting the evaluation of the process, taking into account the FAs concentration effect. The BMP yields varied between 304 (5 % FAs) and 502 NmL CH 4 g VSadded −1 (30 % FAs). The next step in this work was the mathematical modeling of CH 4 production, where the proposed model could satisfactorily simulate the biological process with R2 = 0.94 for all the studied experiments. Such a model can be a valuable tool for deciding on the most appropriate biomass utilization option and the description of AD with dual-stage CH 4 production. [ABSTRACT FROM AUTHOR]

Algal oligosaccharides, derived from polysaccharides in algal biomass, exhibit bioactive properties that enhance plant antioxidant enzyme activity and free radical scavenging. Currently, algal oligosaccharides are mainly produced from large algae, while studies on preparing algal oligosaccharides from microalgae are relatively insufficient. This study focuses on utilizing Chlorella cultivated under controlled conditions using diluted livestock wastewater to produce algal oligosaccharides and investigates their impact on rice seed germination under salt stress. Results show that culturing Chlorella with diluted livestock wastewater not only stimulated algal growth but also efficiently removed nitrogen, phosphorus, and other nutrients. Algal oligosaccharides demonstrated significant improvements in rice seed germination, vigor indices, biomass accumulation, and nitrogen absorption under salt stress. Physiological indicators revealed elevated osmotic adjustment substances, increased chlorophyll content, and alleviated oxidative damage in rice seedlings treated with algal oligosaccharides. The study introduces an innovative method of using livestock wastewater for algal oligosaccharides production, emphasizing its dual benefits including efficient resource utilization and significant cost reduction. The findings also support the theoretical application of Chlorella -derived algal oligosaccharides in enhancing rice cultivation under salt stress. • The oligosaccharides were prepared from Chlorella vulgaris cultured in wastewater, and the production cost was reduced. • studied the effects of Chlorella oligosaccharides on the germination of rice seeds under high salinity conditions. • Under salt stress, Algal oligosaccharides have significantly improved various physiological indicators of rice seeds. [ABSTRACT FROM AUTHOR]

Waste tires (WT) are difficult to degrade in natural conditions, but co-pyrolysis with other substances can release environmental pressure. Thus, microwave catalytic co-pyrolysis of WT and Chlorella vulgaris (CV) were studied. The effects of material mixing ratio, catalysts (NiO, CoO and CeO) and their addition amounts (5%, 10%, 15% and 20%) on the co-pyrolysis were analyzed. The results showed that bio-oil yield was boosted by co-pyrolysis and the maximum value (19.77%) appeared at C6W4 (CV:WT = 6:4). While adding 15%NiO, the maximum yield of bio-oil increased by 8.66%. Compared with CV pyrolysis alone, the deoxidation rate, denitrification rate, and desulfurization rate of C6W4 were as high as 44.57%, 59.82% and 52.59%, respectively. Catalysts improved the quality of bio-oil, the highest hydrocarbon content (58.3%) and denitrification rate (27.07%) were obtained at the 15%NiO. The highest aromatic hydrocarbon content (33.2%) and deoxygenation rate (10.31%) appeared in 15%CoO. [Display omitted] • CV and WT co-pyrolysis with different mixing ratios and catalysts. • Co-pyrolysis improved the yield and quality of bio-oil. • The addition of 15% NiO promoted the co-pyrolysis characteristic significantly. • Catalysts increased the hydrocarbons and reduced nitrogen and oxygen compounds. • 15%NiO had the largest hydrocarbon content and denitrification rate. [ABSTRACT FROM AUTHOR]

The study investigated the potential of wastewater-derived microalgae as a cost-effective feedstock for bioethanol production. The influence of CO 2 loading, use of swine wastewater as a nutrient source, effect of micronutrients in the cultivation media, and scale-up of Chlorella vulgaris FSP-E was conducted. Results showed that 2% CO 2 , 25% swine wastewater, 500 mg/L sodium nitrate, 40 mg/L K 2 HPO 4 , 75 mg/L MgSO 4 , and 6 mg/L citric acid were optimal for maximal biomass production, nitrate removal, and carbohydrate accumulation in BG-11 medium. The maximum biomass and carbohydrate content obtained in this study were 35-fold and 60%, respectively. Scaling up to 5 L volume was challenging due to illumination, aeration, and mixing issues. The obtained carbohydrate-rich biomass was subjected to mild sulfuric acid hydrolysis and subsequently used for bioethanol fermentation. The hydrolysate was composed solely of glucose and galactose and was converted into bioethanol within 8 h by Saccharomyces cerevisiae with an ethanol yield of 0.22 ± 0.01 g ethanol per g biomass. Further exploration of effective lighting and mixing strategies are recommended to realize economically viable microalgal biofuels. [Display omitted] • 2% CO 2 build-up hinders growth, which is vital for optimizing the photobioreactor • Swine waste at 25% concentration excels as an alternative nutrient source • 500 mg/L nitrate concentration maximizes biomass yield with the lowest residual N • Scaling up reactor volume by five times reduces biomass production by 50% • Scaled-up Chlorella vulgaris FSP-E culture yields 8.98 g/L ethanol in 8 h [ABSTRACT FROM AUTHOR]

Contributing to the assessment of potential physiological changes in microalgae subjected to different concentrations and types of cyanotoxins, this study investigated the inhibitory effects of cyanotoxins on the growth, density, biomass, and ecotoxicity of Chlorella vulgaris. Chlorella vulgaris was exposed to crude extracts of cyanobacteria producing microcystin-LR (MC-LR), saxitoxin (SXT), anatoxin-a (ATX-A), and cylindrospermopsin (CYN) with initial concentrations of 5.0, 2.05, 0.61, and 1.42 μg.L−1, respectively. The experiments were conducted under controlled conditions, and monitoring of growth and cell inhibition occurred at 24h, 48h, 72h, and 96h. Chlorophyll-a content and ecotoxicity assessment were conducted with samples collected after 96h of exposure to cyanotoxins. The growth assays of Chlorella vulgaris , with results expressed in terms of average growth rates (doublings/day), indicated the following order for cyanotoxins: SXT (2.03) > CYN (1.66) > MC-LR (1.56) > ATX-A (0.18). This assay revealed the prominent inhibitory potential of ATX-A on Chlorella vulgaris growth compared to the other toxins evaluated. Regarding the inhibition of the photosynthetic process, expressed in terms of the percentage inhibition of Chlorophyll-a, the following order for cyanotoxins was obtained: ATX-A (82%) > MC-LR (76%) > STX (46%) > CYN (16%). These results also indicated that among the cyanotoxins, ATX-A was the most detrimental to the photosynthetic process. However, contrary to the observations in the growth study, SXT proved to be more harmful than CYN in terms of Chlorophyll-a inhibition. Finally, the results of the toxicity assay revealed that only ATX-A and MC-LR exerted a chronic influence on Chlorella vulgaris under the investigated conditions. [Display omitted] • Phytotoxicity of cyanotoxins induces different physiological responses to Chlorella vulgaris. • MC-LR and ATX-A promote greater inhibitory effects on the growth, density, biomass and ecotoxicity of Chlorella vulgaris. • The lowest inhibitions of algal growth among the cyanotoxins were for SXT and CYN. • The percentage inhibition of Chlorophyll –a was: ATX-A (82%) > MC-LR (76%) > SAX (46%) > CYN (16%). [ABSTRACT FROM AUTHOR]

Doxorubicin (DOX) is a chemotherapy agent associated with adverse effects on male reproductive health. Chlorella vulgaris (ChV) is a potent natural antioxidant with promising applications in maintaining health and preventing oxidative stress-related diseases. The present study aimed to investigate the protective effect of ChV on DOX-induced testicular toxicity. Twenty-five Wistar rats (230 ± 20 g) were randomly assigned to five groups (n = 5), including the control group, sham group (received normal saline by oral gavage daily and intraperitoneally (IP) once a week), DOX group (3 mg/kg; once a week; IP), ChV group (300 mg/kg/day; by oral gavage), and DOX (3 mg/kg; once a week; IP) + ChV (300 mg/kg/day; by oral gavage) group. After 8 weeks of treatment, the rats were euthanized and serum testosterone level, testes histomorphometry, gonadosomatic index (GSI), apoptotic gene expression, oxidative stress index, and sperm parameters were assessed. The results showed that DOX led to a significant decrease in histological indexes, testosterone level, GSI, sperm parameters, and Bcl-2 gene expression and increased expression of P-53 and Bax genes, and oxidative stress markers (P<0.05). The administration of ChV in the DOX+ChV group significantly improved testosterone levels, sperm parameters, testicular tissue apoptosis, antioxidant enzymes, and structural integrity of the testes (P<0.05). The findings suggest that the co-administration of ChV can be a promising therapeutic agent to reduce the adverse effects of DOX on male reproductive performance. [Display omitted] • Doxorubicin induces apoptosis and testicular damage in rat testis. • Doxorubicin reduces sperm quality and induces oxidative stress in the male reproductive system. • Chlorella vulgaris prevents the adverse effects of doxorubicin on the male reproductive system. [ABSTRACT FROM AUTHOR]

Unicellular microalga Chlorella pyrenoidosa is an excellent source of protein, but its ability to produce functional proteins has received less attention. In this study, a strategy to enhance the levels of functional proteins and biomass, by adding sodium selenite under heterotrophic cultivation, is reported for C. pyrenoidosa 038F. Activities of catalase, superoxide dismutase, and glutathione peroxidase were significantly enhanced by 1.94-, 1.90- and 32.73-fold, respectively, in C. pyrenoidosa 038F exposed to 20 mg/L of sodium selenite. Further, western blot analysis confirmed that sodium selenite promoted the synthesis of glutathione peroxidase, which might be due to the up-regulation of peroxisome and selenocysteine-synthesis-related genes. Sodium selenite also increased biomass, the content of protein and soluble sugar by 1.32-, 1.29-, 1.46-fold, respectively. Subsequent transcriptomic analysis confirmed that cellular respiration and the gluconeogenesis pathway were enhanced. This study highlights the potential use of heterotrophic C. pyrenoidosa 038F as a novel selenoprotein-rich carrier while simultaneously producing soluble sugar and biomass. These results might be helpful for increasing economic production of C. pyrenoidosa under heterotrophic cultivation. • The activity and content of glutathione peroxidase in C. pyrenoidosa were enhanced by sodium selenite. • The biomass, protein content and soluble sugar content in C. pyrenoidosa were increased by sodium selenite. • Sodium selenite promoted cellular respiration through increasing tricarboxylic acid cycle and pentose phosphate pathway. • This strategy could facilitate the production of high value-added Chlorella products. [ABSTRACT FROM AUTHOR]

• A deterministic lateral displacement chip was designed to successfully separate Chlorella vulgaris and Haematococcus pluvialis. • Investigated the optimal flow rate ratio between the equal-width sheath inlet and sample inlet. • Explored the maximum throughput the chip can handle while ensuring sorting purity. Microalgae are a group of photosynthetic organisms that can grow autotrophically, performing photosynthesis to synthesize abundant organic compounds and release oxygen. They are rich in nutritional components and chemical precursors, presenting wide-ranging application prospects. However, potential contamination by foreign strains or bacteria can compromise their analytical applications. Therefore, the obtaining of pure algal strains is crucial for the subsequent analysis and application of microalgae. This study designed a deterministic lateral displacement (DLD) chip with dual input and dual outlet of equal width for the separation of Haematococcus pluvialis and Chlorella vulgaris. Optimal separation parameters were determined through a series of experiments, resulting in a purity of 99.80 % for Chlorella vulgaris and 94.58 % for Haematococcus pluvialis , with recovery rates maintained above 90 %, demonstrating high efficiency. This study provides a reliable foundation for future research and applications of microalgae, which holds considerable significance for the subsequent analysis and utilization of microalgae. [ABSTRACT FROM AUTHOR]

• Consider a harmonious balance of adsorption capacity, desorption efficiency, and compatibility with different biochar types in solid-phase extraction (SPE). • Nitrogen-doped chlorella biochar reduces irreversible adsorption while enhancing bamboo biochar's selectivity. • H+ proton equilibrium influences biochar's adsorption-desorption balance. Biochar, a sustainable sorbent derived from pyrolyzed biomass, has garnered attention for its efficacy in solid-phase extraction (SPE) of antibiotics, with a particular focus on tetracyclines (TCs). Despite its recognized potential, the intricate separation mechanisms operative in biochar-based SPE systems have not been fully deciphered. This investigation contrasts chlorella biochar against commercial bamboo biochar, harnessing an array of analytical methodologies-microstructure characterization, adsorption thermodynamics, competitive adsorption kinetics, H+ back titration, and selectivity adsorption studies-complemented by a Box-Behnken design for the optimization of chlorella/bamboo-SPE and subsequent application in the analysis of animal-derived foodstuffs. The study unveils that a hybrid sorbent, integrating nitrogen-doped microporous chlorella biochar with mesoporous bamboo biochar in a 95/5 mass ratio, markedly diminishes irreversible adsorption while enhancing selectivity, surpassing the performance of single biochar SPE systems. The elucidated separation mechanisms implicate a partition model, propelled by oxygen-rich functional groups on chlorella biochar and the rapid adsorption kinetics of bamboo biochar, all orchestrated by electrostatic interactions within the mixed biochar framework. Moreover, the synergy of mixed biochar-SPE with high-performance liquid chromatography (HPLC) demonstrates exceptional proficiency in detecting TCs in animal viscera, evidenced by recovery rates spanning 80.80 % to 106.98 % and RSDs ranging from 0.24 % to 14.69 %. In essence, this research not only sheds light on the multifaceted factors influencing SPE efficiency but also propels the use of biochar towards new horizons in environmental monitoring and food safety assurance. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Chlorella vulgaris refined into protein, fatty acids, bioethanol, and biogas. • Cascading process boosts bioethanol yield by 25% and biomethane by 22.4%. • Biorefinery supplies CO 2 for cultivation and solvent for fatty acid extraction. • The biorefinery significantly reduces GHG emissions and associated social costs. • The biorefinery offers a comprehensive and scalable solution for industrialization. An integrated biorefinery was developed that utilizes microalgal biomass, Chlorella vulgaris , to sustainably produce proteins, fatty acids, bioethanol, and biogas. The microalgal soluble proteins and fatty acids were initially extracted through a cascading extraction process, including bead milling and solvent extraction. Subsequently, the investigation focused on utilizing the biomass residues for bioethanol and biogas production, ultimately improving energy recovery. Implementing the cascading process resulted in a 25 % enhancement in bioethanol yield and a 22.4 % increase in biomethane yield compared to untreated biomass. This approach resulted in 78.0 g of protein, 50.9 g of lipid, 20.8 ml of ethanol, and 136.5 L of methane from one kilogram of dry C. vulgaris biomass. Considering the potential of 8,640 k tons of annual microalgae production in Iran, an estimated 4.1 million tons of CO2 emissions could be averted. This reduction could result in saving approximately 1394.8 million USD in associated social costs of carbon. These improvements in fully valorizing biomass through practical cascading methods significantly advance microalgal biorefinery. [ABSTRACT FROM AUTHOR]

Screening for sensitive toxicological indicators and understanding algal tolerance to pharmaceutical contaminants (PhCs) are essential for assessing PhCs risk and their removal by microalgae. Carbamazepine (CBZ) showed adverse effects on microalgae, but the specific toxicity mechanisms on the most sensitive algal photosynthetic system (PS) remain limited. This study delved into the impact of CBZ exposure on the growth, cell viability, pigment content, and PS of Chlorella vulgaris. The findings revealed a notable inhibition of C. vulgaris growth by CBZ, with an IC 50 value of 27.2 mg/L at 96 h. CBZ exposure induced algal membrane damage and cell viability. Intriguingly, CBZ drastically diminished intracellular pigment levels, notably showing "low promotion and high inhibition" of chlorophyll b (Chl b) by 72 h. Moreover, the study identified a decreased number of active reaction centers (RCs) within algal PSII alongside inhibited electron transport from Q A to Q B on the PSII receptor side, leading to PSII disruption. As an adaptive response to CBZ stress, C. vulgaris stimulated its Chl b synthesis, increased non-photochemical quenching (NPQ), and adapted its tolerance to bright light. Additionally, the alga attempted to compensate for the CBZ-induced reduction in electron transfer efficiency at the PSII receptor side and light energy utilization by increasing its electron transfer from downstream. Principal component analysis (PCA) further verified that the parameters on non-photochemical dissipation, electron transport, and integrative performance were the most sensitive algal toxicological indicators for CBZ exposure, and algal PS has energy protection capability through negative feedback regulation. However, prolonged exposure to high doses of CBZ will eventually result in permanent damage to the algal PS. Hence, attention should be paid to the concentration of CBZ in the effluent and the exposure time, while methods to mitigate algal photodamage should be appropriately sought for algal treatment of dense effluents. [Display omitted] • CBZ inhibited algal growth, compromised cell viability and pigments level. • CBZ decreased RCs number and inhibited electron transport on PSII receptor side. • CBZ enhanced electron transfer from downstream as a compensation. • PCA results revealed the most sensitive algal toxicological indicators. • Algal PS has energy protection capability through negative feedback regulation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The optimal pulp ratio ranges from 0.2 % to 0.6 %. • Pigments and Ca-Mg ATPase enzyme increased up to 10 % in the culture with bauxite. • Chlorella vulgaris was the most promising one than other microalgae species. • The optimal aeration rate ranged from 0.4 vvm to 1.2 vvm. • HRT 4d recovered REEs two times higher than HRT 3d. Biomining using microalgae has emerged as a sustainable option to extract rare earth elements (REEs). This study aims to (i) explore the capability of REEs recovery from bauxite by microalgae, (ii) assess the change of biochemical function affected by bauxite, and (iii) investigate the effects of operating conditions (i.e., aeration rate, pH, hydraulic retention time) to REEs recovery. The results showed that increasing bauxite in microalgae culture increases REEs recovery in biomass and production of biochemical compounds (e.g., pigments and Ca-Mg ATPase enzyme) up to 10 %. The optimum pulp ratio of bauxite in the microalgae culture ranges from 0.2 % to 0.6 %. Chlorella vulgaris was the most promising, with two times higher in REEs recovery in biomass than the other species. REEs accumulated in microalgae biomass decreased with increasing pH in the culture. This study establishes a platform to make the scaling up of REEs biomining by microalgae plausible. [ABSTRACT FROM AUTHOR]

[Display omitted] • The synthesis of polysaccharides from six Chlorella strains was studied. • Two of the Chlorella strains studied had higher polysaccharide productivity. • C. kessleri produced more neutral sugars than the studied strains. • C. sorokiniana produced more uronic acids than the strains studied. Microalgae are known to be the richest natural source of polysaccharides. The study aimed to evaluate the ability of microalgae from the Chlorella sp. genus to synthesize polysaccharides. Brody & Emerson max medium proved to be the most effective; the average cell content in the culture fluid at the beginning and at the end of cultivation for IPPAS Chlorella pyrenoidosa Chick was 1.23 ± 0.03 g/L and 1.71 ± 0.20 g/L, respectively. With a high average dry weight of IPPAS Chlorella pyrenoidosa Chick (4.45 ± 0.10 g/L), it produced the least amount of neutral sugars (0.75 ± 0.02 g/L) and uronic acids (0.14 ± 0.01 mg/L). The microalga IPPAS Chlorella vulgaris with the lowest average dry weight (1.18 ± 0.03 g/L) produced 0.80 ± 0.02 g/L of neutral sugars and 0.17 ± 0.01 mg/L of uronic acids. Microalgal polysaccharides have the potential to be used as a source for biologically active food additives, as they contain various types of polysaccharides that can be beneficial to human health. [ABSTRACT FROM AUTHOR]

[Display omitted] • Buoyant barium alginate bubble beads (BABB) boosted the growth of immobilized microalgae. • BABB reduced the leakage of microalgae by 80% over traditional calcium alginate beads (CAB). • BABB enabled rapid microalgal biomass separation and full freeze−drying in 3.5 h. • Three strategic BABB optimizations were introduced for further enhanced culture. • Optimized BABB in open raceway pond reactor achieved 0.609 mg/bead biomass in 7 days. Microalgae immobilization in alginate beads shows promise for biomass production and water pollution control. However, carrier instability and mass transfer limitations are challenges. This study introduces buoyant barium alginate bubble beads (BABB), which offer exceptional stability and enhance Chlorella vulgaris growth. In just 12 days, compared to traditional calcium alginate beads, BABB achieved a 20 % biomass increase while minimizing cell leakage and simplifying harvesting. BABB optimization involved co-immobilization with BG-11 medium, enrichment of CO 2 in internal bubbles, and the integration of Fe nanoparticles (FeNPs). In the open raceway pond reactor, these optimizations resulted in a 39 % increase in biomass over 7 days compared to the unoptimized setup in closed flasks. Furthermore, enhancements in pigment and organic matter production were observed, along with improved removal of ammonia nitrogen and phosphate. These results highlight the overall advantages of BABB for microalgae immobilization, offering a scientific foundation for their effective utilization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu 2 O/BC/SA-SA double-layer coatings were designed and prepared. • Cu 2 O/BC-SA coating was prepared and modified by NaCl for porous structure. • Efficiency layer has a faster release rate of Cu2+. • Large capacity photobioreactor was designed to test antifouling property. • 3 wt% NaCl modifying coating has the best antifouling property against microalgae. In order to pursue optimize antifouling performance and protect the metal substrate from direct contact with external environment, the sodium chloride (NaCl) modified cuprous oxide (Cu 2 O)/Biochar (BC)/styrene-acrylic (SA)-SA double-layer coatings with the effective and controllable release rate of Cu2+ were prepared. The NaCl particles were dispersed and dissolved in the Cu 2 O/BC/SA layer (the functional layer) as the pore-forming agent, which can increase the contact between Cu 2 O/BC and external environment in order to control the release rate of Cu2+ of coatings. A large capacity photobioreactor was designed to conduct adhesion tests of marine microalgae Nannochloropsis oceanica (N. oceanica) and fresh Chlorella vulgaris (C. vulgaris) on the coatings, aiming to evaluate the antifouling performance. Results show that the Cu 2 O/BC/SA-SA coating modified with 3 wt% NaCl possesses the best antifouling property, which is 63.7 % higher than that of unmodified coating and 92.8 % higher than that of pure SA membrane. [ABSTRACT FROM AUTHOR]

• Power density of BPVs increased from 10-4 mW/m2 to 103 mW/m2 since 2006. • Synechocystis and Chlorella are two dominant species for high bioelectricity. • EET of OPMs is mainly mediated by membrane proteins rather than nanowires. • Regulation techniques of BPVs range from biofilm to external environment. • Future directions to EET mechanisms, modular devices, and novel technologies. The development of carbon–neutral fuel sources is an essential step in addressing the global fossil energy crisis. Whole-cell biophotovoltaic systems (BPVs) are a renewable, non-polluting energy-generating device that utilizes oxygenic photosynthetic microbes (OPMs) to split water molecules and generate bioelectricity under the driving of light energy. Since 2006, BPVs have been widely studied, with the order magnitudes of power density increasing from 10-4 mW/m2 to 103 mW/m2. This review examines the extracellular electron transfer (EET) mechanisms and regulation techniques of BPVs from biofilm to external environment. It is found that the EET of OPMs is mainly mediated by membrane proteins, with terminal oxidase limiting the power output. Synechocystis sp. PCC6803 and Chlorella vulgaris are two species that produce high power density in BPVs. The use of metal nanoparticles mixing, 3D pillar array electrodes, microfluidic technology, and transient-state operation models can significantly enhance power density. Challenges and potential research directions are discussed, including a deeper analysis of EET mechanisms and dynamics, the development of modular devices, integration of multiple regulatory components, and the exploration of novel BPV technologies. [ABSTRACT FROM AUTHOR]

• Toxicity of aged PVC MPs is greater than that of virgin PVC MPs. • MPs affect the growth and intracellular components of C. pyrenoidosa. • MPs promote nitrate uptake and inhibit photosynthesis of C. pyrenoidosa. • Extracellular polymeric substances increase during exposure to aged MPs. • The toxicity of MPs was associated with intercellular oxidative stress levels. The toxicity of microplastics (MPs) on freshwater plants has been widely studied, yet the influence of aged MPs remains largely unexplored. Herein, we investigated the influence of polyvinyl chloride (PVC) MPs, both before and after aging, at different environmentally relevant concentrations on Chlorella pyrenoidosa , a freshwater microalgae species widely recognized as a valuable biomass resource. During a 96-h period, both virgin and aged MPs hindered the growth of C. pyrenoidosa. The maximum growth inhibition rates were 32.40 % for virgin PVC at 250 mg/L and 44.72 % for aged PVC at 100 mg/L, respectively. Microalgae intracellular materials, i.e., protein and carbohydrate contents, consistently decreased after MP exposure, with more pronounced inhibition observed with aged PVC. Meanwhile, the MP aging significantly promoted the nitrogen uptake of C. pyrenoidosa , i.e., 1693.45 ± 42.29 mg/L (p < 0.01), contributing to the production of humic acid-like substances. Additionally, aged PVC induced lower chlorophyll a and Fv/Fm when compared to virgin PVC, suggesting a more serious inhibition of the photosynthesis process of microalgae. The toxicity of MPs to C. pyrenoidosa was strongly associated with intercellular oxidative stress levels. The results indicate that MP aging exacerbates the damage to photosynthetic performance and bioenergy production in microalgae, providing critical insights into the toxicity analysis of micro(nano)plastics on freshwater plants. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Bio-metabolites in microalgae were extracted using deep eutectic solvents. • Extracts contained proteins, carotenoids, phenolics, carbohydrates, and lipids. • Bio-active compounds from microalgae were obtained by ultrasound-assisted extraction. • Deep eutectic solvents showed positive results for the extraction of bio-metabolites. Microalgae biomass contains proteins, polysaccharides, carotenoids, phenolic compounds, vitamins, minerals, and other valuable compounds. In the extraction process of useful intracellular products from biomass, deep eutectic solvents (DESs) offer several advantages as an alternative to organic solvents. This study used deep eutectic solvents as extraction media to obtain bio-active compounds from freeze-dried microalgae biomass. This study aimed to evaluate the effect of two different DESs (Choline chloride: acetic acid (1:2) (CCA) and Choline chloride: urea (1:2) (CCU)) on the extraction of lipids, carotenoids, proteins, phenolic compounds, and carbohydrates from different microalgae biomass including Schizochytrium sp., Chlorella vulgaris , Scenedesmus protuberans and Neochloris texensis. The best results were obtained as follows: proteins from CCA- N. texensis (28.99 mg/g DW), carotenoids from CCA- S. protuberans (33.55 mg/g DW), phenolics from CCA- S. protuberans (33.44 mg GAE/g DW), carbohydrates from CCA- S. protuberans (18.32 mg/g DW), and lipids (the treated biomass pellets) from CCU- N. texensis (18.3 %). UV-spectrophotometry, LC–MS/MS, and GC–MS were used to analyse the carotenoid, phenolic, and lipid content, respectively. [ABSTRACT FROM AUTHOR]

In recent years, a growing concern has emerged regarding the environmental implications of flame retardants (FRs) like tetrabromobisphenol-A (TBBPA) and graphene family nanomaterials (GFNs), such as graphene, graphene oxide (GO), and reduced graphene oxide (rGO), on marine biota. Despite these substances' well-established individual toxicity profiles, there is a notable gap in understanding the physicochemical interactions within the binary mixtures and consequent changes in the toxicity potential. Therefore, our research focuses on elucidating the individual and combined toxicological impacts of TBBPA and GFNs on the marine alga Chlorella sp. Employing a suite of experimental methodologies, including Raman spectroscopy, contact angle measurements, electron microscopy, and chromatography, we examined the physicochemical interplay between the GFNs and TBBPA. The toxicity potentials of individual constituents and their binary combinations were assessed through growth inhibition assays, quantifying reactive oxygen species (ROS) generation and malondialdehyde (MDA) production, photosynthetic activity analyses, and various biochemical assays. The toxicity of TBBPA and graphene-based nanomaterials (GFNs) was examined individually and in combinations. Both pristine TBBPA and GFNs showed dose-dependent toxicity. While lower TBBPA concentrations exacerbated toxicity in binary mixtures, higher TBBPA levels reduced the toxic effects compared to pristine TBBPA treatments. The principal mechanism underlying toxicity was ROS generation, resulting in membrane damage and perturbation of photosynthetic parameters. Cluster heatmap and Pearson correlation were employed to assess correlations between the biological parameters. Finally, ecological risk assessment was undertaken to evaluate environmental impacts of the individual components and the mixture in the algae. [Display omitted] • The toxicity of TBBPA towards algal cells was concentration-dependent. • TBBPA showed an increment in the oxidative stress generation in algal cells. • At lower concentrations of TBBPA, TBBPA + GFNs showed increase in toxic effects. • At higher concentrations of TBBPA, TBBPA + GFNs showed decrease in toxic effects. • The risk quotient of TBBPA towards the algae reduced in the presence of GFNs. [ABSTRACT FROM AUTHOR]

This study investigates the phycoremediation potential of microalgae Chlorella vulgaris in the degradation of Direct green 6 (DG6), a synthetic azo dye commonly used in the textile industry, which poses significant environmental and health risks due to its toxic and carcinogenic properties. Over 50 days of treatment, we analyzed the effects of varying concentrations of DG6 on the biodegradation capabilities of C. vulgaris with the characterization of growth and antioxidant parameters. The findings demonstrate that C. vulgaris reduced DG6 levels significantly (p < 0.05) at higher temperatures (40 °C) compared to other environmental ambient temperatures. Within the acidic range pH < 7 progressive removal efficiency was observed within 25 days in consistency with the enhanced growth indices of biomass concentration (X m), productivity (P x), specific growth rate (μ m), and doubling time (t d) at the higher concentration of 60 mg L−1. Induction of both enzymatic and non-enzymatic antioxidant activities were quantified for superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), azoreductase, and laccase, as well as changes in the total ascorbate pool (AsA + DHA) and ferric reducing antioxidant power (FRAP). Furthermore, the underlying biodegradation mechanisms were elucidated by identifying the reductive cleavage of azo bonds by azoreductase and breakdown by peroxidases and laccase. These molecular by-products were identified using gas chromatography–mass spectrometry (GC–MS), which shed light on the metabolic pathways involved in DG6 biodegradation. This study underscores the effectiveness of C. vulgaris as a sustainable, low-cost solution for the bioremediation of azo-dye-polluted water. This study lays the groundwork for further exploration into the genetic and metabolic adaptations of algae under complex organic pollutant stress, with potential implications for ecophysiology, biotic interactions, and evolutionary biology. [Display omitted] • C. vulgaris growth evidenced efficient utilization of Direct Green 6 (DG6) as substrate. • The optimum DG6 removal positively linked to temperatures raise and acidic conditions. • Exposure to DG6 prompted induction of antioxidant enzymes under different treatments. • Phycoremediation of DG6 by C. vulgaris is a sustainable approach in environmental remediation. [ABSTRACT FROM AUTHOR]

Microalgae-derived biostimulants are increasingly used as viable tools to improve growth, yield of crops, and reduce agricultural environmental footprint. However, microalgae isolated from aquatic environments are the main strains used in the production of biostimulants. This study aims to evaluate the biostimulant effect of a terrestrial Chlorella vulgaris strain isolated from arid soil on germination and growth of wheat (Triticum aestivum, var. Achtar). Different concentrations 0.2 %, 0.5 %, 25 % and 50 % (v /v) of four C. vulgaris treatments (aqueous extract, filtered culture, crude culture and sonified culture) were investigated by measuring several biometric parameters to assess wheat germination and growth performance. All C. vulgaris treatments significantly enhanced wheat germination and growth with concentration dependent effect. The crude culture and filtrate at 25 % were the most effective compared to untreated plants. They significantly improved wheat germination index by 16.86 %, germination rate coefficient by 7.87 %, germination energy by 20.40 % as well as growth parameters such as root length (62.82 % and 52.84 %), stem length (71.36 % and 59.19 %), and root (662.5 % and 391.67 %) and stem dry biomass (675 % and 370.83 %), respectively. Principal Component Analysis (PCA) revealed that crude culture and filtrate at the lowest doses of 0.5 and 25 % were closely correlated to enhanced wheat root and shoot length and dry weight. The plant nutrients, mineral elements, chlorophyll a , total proteins and carbohydrates contents were positively correlated with enhanced shoot length and dry weight. The soil physicochemical properties were significantly increased under all C. vulgaris treatments at higher dose (50 %) whereas plants N and P contents enhancement was correlated to the soil nutrients increase. Thus, the results highlighted the potential of soil microalgae as an eco-friendly biostimulant for promoting sustainable agriculture. • Soil Chlorella vulgaris significantly enhanced wheat germination and growth. • C. vulgaris treatments displayed concentration-dependent effect on wheat growth. • Crude culture and filtrate effectively improved wheat growth at the lowest doses. • Higher dosages of C. vulgaris negatively affect the germination process and growth. • Wheat dry biomass of aboveground and belowground plant parts improved by over 600 %. [ABSTRACT FROM AUTHOR]

Globally, agricultural productivity is facing a serious problem due to soil salinity which often causes osmotic, ionic, and redox imbalances in plants. Applying halotolerant rhizobacterial inoculants having multifarious growth-regulating traits is thought to be an effective and advantageous approach to overcome salinity stress. Here, salt-tolerant (tolerating 300 mM NaCl), exopolysaccharide (EPS) producing Rhizobium azibense SR-26 (accession no. MG063740) was assessed for salt alleviation potential by inoculating Phaseolus vulgaris (L.) plants raised under varying NaCl regimes. The metabolically active cells of strain SR-26 produced a significant amount of phytohormones (indole-3-acetic acid, gibberellic acid, and cytokinin), ACC deaminase, ammonia, and siderophore under salt stress. Increasing NaCl concentration variably affected the EPS produced by SR-26. The P-solubilization activity of the SR-26 strain was positively impacted by NaCl, as demonstrated by OD shift in NaCl-treated/untreated NBRIP medium. The detrimental effect of NaCl on plants was lowered by inoculation of halotolerant strain SR-26. Following soil inoculation, R. azibense significantly (p ≤ 0.05) enhanced seed germination (10%), root (19%) shoot (23%) biomass, leaf area (18%), total chlorophyll (21%), and carotenoid content (32%) of P. vulgaris raised in soil added with 40 mM NaCl concentration. Furthermore, strain SR-26 modulated the relative leaf water content (RLWC), proline, total soluble protein (TSP), and sugar (TSS) of salt-exposed plants. Moreover, R. azibense inoculation lowered the concentrations of oxidative stress biomarkers; MDA (29%), H 2 O 2 content (24%), electrolyte leakage (31%), membrane stability (36%) and Na+ ion uptake (28%) when applied to 40 mM NaCl-treated plants. Further, R. azibense increases the salt tolerance mechanism of P. vulgaris by upregulating the antioxidant defensive responses. Summarily, it is reasonable to propose that EPS-synthesizing halotolerant R. azibense SR-26 should be applied as the most cost-effective option for increasing the yields of legume crops specifically P. vulgaris in salinity-challenged soil systems. [Display omitted] • Exopolysaccharide producing Rhizobium azibense tolerated NaCl (300 mM). • R. azibense synthesized phytohormones and other bioactive molecules under NaCl stress. • Detrimental effect of NaCl on P. vulgaris was alleviated following bacterial inoculation. • R. azibense lowered oxidative stress biomarkers, membrane stability and Na+ ion concentrations. • R. azibense improved salt tolerance mechanism in P. vulgaris by upregulating antioxidant defense responses. [ABSTRACT FROM AUTHOR]

[Display omitted] • The relative abundance of potential ARGs hosts decreased in algal-bacterial system. • New algal-bacterial relationship formed between C. vulgaris and in-situ bacteria. • The effect size of ARGs removal will be affected by algicidal bacteria and the MGEs. Antibiotic resistance genes (ARGs) have exhibited significant ecological concerns, especially in the urban water that are closely associated with human health. In this study, with presence of exogenous Chlorella vulgaris - Bacillus licheniformis consortium, most of the typical ARGs and MGEs were removed. Furthermore, the relative abundance of potential ARGs hosts has generally decreased by 1–4 orders of magnitude, revealing the role of algal-bacterial consortium in cutting the spread of ARGs in urban water. While some of ARGs such as macB increased, which may be due to the negative impact of algicidal bacteria and algal viruses in urban water on exogenous C. vulgaris and the suppression of exogenous B. licheniformis by indigenous microorganisms. A new algal-bacterial interaction might form between C. vulgaris and indigenous microorganisms. The interplay between C. vulgaris and bacteria has a significant impact on the fate of ARGs removal in urban water. [ABSTRACT FROM AUTHOR]

• Higher light intensity improves Chlorella vulgaris growth and productivity. • Maximum biomass productivity was 171 ± 13 mg dw L−1 d−1 under 1107 μmol m−2 s−1 light. • Higher nutrient assimilation achieved with increasing light intensity. • High light intensity promoted lipid and carbohydrate accumulation. It is urgent to find alternatives to fossil fuels to mitigate the effects of climate change. High light intensity during microalgal growth can promote lipid and carbohydrate accumulation (feedstocks to biofuels). However, more research needs to be done concerning the effect of this factor on microalgal productivity and biochemical composition from a growth phase point of view. This study evaluated the impact of high light intensities (291, 527 and 1107 μmol m−2 s−1) on Chlorella vulgaris growth in synthetic wastewater, nutrient assimilation and biochemical composition in late-exponential and stationary growth phases. Under the highest light intensity, a higher growth rate (0.54 ± 0.02 d−1) and maximum productivity (166 ± 13 mg/L d−1) were achieved. Also, nutrient removal efficiencies at the late-exponential phase reached 97.0 ± 0.2 % and 98.2 ± 0.1 % for nitrogen and phosphorus, respectively. Under all light intensities tested at the stationary phase, microalgae also achieved high nutrient removal efficiencies (>95 %). Extreme light intensity (1107 μmol m−2 s−1) boosted the accumulation of carbohydrates (30 ± 3 % w/w) and lipids (13.0 ± 0.4 % w/w). Under lower light intensities, the content of these compounds did not change significantly between growth phases. The chlorophyll content decreased with the increasing light intensity and increasing exposure time. Exposing C. vulgaris to high light intensity seems promising to simultaneously treat wastewater and boost lipid and carbohydrate accumulation, which can be used for biofuel production. [ABSTRACT FROM AUTHOR]