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Abstract\nNOVELTY STATEMENTIn this study, three microalgae species were cultivated using dairy and fish wastewater: Haematococcus pluvialis, Coelastrella saipanensis, and Chlorella sp. The process involved manipulating various physicochemical conditions, to determine optimal growth parameters. Our evaluation considered cell count, biomass productivity, specific growth rate, pigments, carbohydrates, proteins, lipid compositions, and cellulose stored in microalgae. A significant observation of highest cellulose accumulation was recorded in C. saipanensis cultivated in dairy waste (DW) medium (2.54 ± 0.042 µg/mg). In contrast, the species grown in fish waste (FW) media recorded a lower level (0.9405 ± 0.06 µg/mg) of cellulose. In DW, H. pluvialis and C. saipanensis accumulated substantial amounts of astaxanthin and carotenoid, respectively. Carbohydrate, protein, and lipid accumulation was maximized in DW culture, with H. pluvialis exhibiting a more incredible carbohydrate content. Lipid analysis showed as Chlorella sp. was capable of accumulating alpha-linolenic acid. The disparity may be attributed to DW’s nutritional and mineral content, which encourages cellulose deposition. The FTIR analysis confirmed the accumulation of cellulose. These findings underscore the potential of DW and FW media as valuable resources for microalgal biofuel and ethanol production, offering a hopeful future for sustainable energy production.The comparative analysis of microalgae cultivated in DW and FW water reveals distinct carbon sequestration patterns and bio-capture potential, observed from this study. In fact, this study identified C. saipanensis, which thrives exceptionally well in DW water and accumulate cellulose, a unique finding that pave the way on further research in this species on bioenery sequestration. By confirming the feasibility of bioproducts harvesting through compound analysis, this study highlights the potential of DW and FW as cheap nutrient resources for microalgae biomass generation, paving the way to bioremediation. [ABSTRACT FROM AUTHOR]

This study investigates the potential of Chlorella vulgaris for nutrient removal and biomass production in synthetic wastewater. The experiments were conducted in 2 L photobioreactors under controlled aeration, agitation, and lighting conditions for 19 days. Despite a moderate growth rate (0.137 d−1), C. vulgaris achieved efficient pollutant removal, with 97% of nitrate, 90% of nitrite, and 90.6% of COD eliminated. Additionally, the biomass was processed to extract fatty acids, yielding a 20% extraction rate, indicating its potential as a biofuel feedstock. These results demonstrate C. vulgaris's dual function in wastewater remediation and biofuel production, presenting a sustainable and economically viable approach to addressing environmental challenges. [ABSTRACT FROM AUTHOR]

Improving photobioreactor performance for microalgae cultivation has been the aim of many researchers over the past few years. One of the primary challenges associated with existing photobioreactors is light penetration. An effective photobioreactor design should maximize light penetration, ensuring uniform illumination throughout the reactor. This study aims to assess the impact of light intensity on microalgal growth from the perspective of energy efficiency and productivity in two photobioreactors. A novel cactus-like and a cylindrical photobioreactor were designed and fabricated using three-dimensional printing technology. These two photobioreactors were used to cultivate two strains of microalgae. The novel photobioreactor achieved a maximum biomass productivity of 1 g/L/d and a maximum energy efficiency of 0.31 g/d/kWh. The cylindrical photobioreactor reached a maximum biomass productivity of 0.74 g/L/d and energy efficiency of 0.22 g/d/kWh. The increase in biomass productivity can be linked to enhancements in the photobioreactor's surface-to-volume ratio and better light utilization. [ABSTRACT FROM AUTHOR]

In this study, iron oxide nanoparticles (IONPs) were employed as an efficient chemical additive to enhance the Chlorella sp. biomass growth and lipid content. A novel strategy was developed to promote biomass growth and lipid content. Treatment with 20 mg/L followed by an additional 40 mg/L concentration of IONPs increased biomass and lipid content of Chlorella sp. by 53% and 67%, respectively, compared with the control. The hydrolyzate of 20 mg/L IONPs treated biomass residues obtained after combined hydrolysis showed maximum reducing sugars content of 41% dry cell weight (dcw), which was further used as substrate for dark fermentative hydrogen production mediated by Enterobacter aerogenes. The optimized concentration of IONPs supplementation in the dark fermentation system yielded 2.6 mol H 2 /mol sugar with acetate as predominant end metabolite. Hence, the present study demonstrated that the IONPs supplementation was a suitable chemical catalyst for biomass and biofuel production. [Display omitted] • 20 mg/L iron oxide nanoparticle supplementation enhances Chlorella sp. biomass • 60 mg/L iron oxide nanoparticle supplementation enhances Chlorella sp. lipid content • Biomass residues pretreated with combined hydrolysis produces 41% total reducing sugar • Iron oxide nanoparticle supplementation enhances dark fermentative hydrogen production • 30 mg/L iron oxide nanoparticle supplementation produces 2.6 mol H 2 /mol sugar [ABSTRACT FROM AUTHOR]

Artemia salina enrichment is limited by the high cost and availability of commercial microalgae culturing media. This study was conducted to evaluate the nutritional value of Artemia salina nauplii enriched with Chlorella vulgaris grown in Bold's Basal Medium (BBM, commercial media) and banana stem compost extract (BSCE) as the alternative low-cost media. The C. vulgaris was cultured in the laboratory and fed to Artemia nauplii hatched as per standard protocols and, after that, analyzed for nutritional values. Artemia fed BSCE-cultured C. vulgaris had significantly (p <.05) higher carbohydrates, total polyunsaturated fatty acids (PUFAs), and monounsaturated fatty acids, but lower saturated fatty acids (SFAs), while protein and lipids were the same as those fed BBM-cultured C. vulgaris. It was concluded that BSCE can replace BBM as an alternative microalgae culturing media and produce an ideal enrichment diet for fish larvae nutrition because of high PUFAs and lower SFAs. [ABSTRACT FROM AUTHOR]

This study investigates the potential of Chlorella vulgaris for nutrient removal and biomass production in synthetic wastewater. The experiments were conducted in 2 L photobioreactors under controlled aeration, agitation, and lighting conditions for 19 days. Despite a moderate growth rate (0.137 d−1), C. vulgaris achieved efficient pollutant removal, with 97% of nitrate, 90% of nitrite, and 90.6% of COD eliminated. Additionally, the biomass was processed to extract fatty acids, yielding a 20% extraction rate, indicating its potential as a biofuel feedstock. These results demonstrate C. vulgaris’s dual function in wastewater remediation and biofuel production, presenting a sustainable and economically viable approach to addressing environmental challenges.

Waste-activated sludge disposal has now become a serious global problem. After pretreatment, sludge was hydrolyzed and acidified to release nutrients. The effects of different sludge pretreatments on microalgal growth and contaminants in a hydrolysis acidification solution were compared. Alkalinization (NaOH), ultrasound (US), and combined pretreatment techniques (US-NaOH) all promoted contaminants' release from the sludge by triggering microbial cell wall rupture and extracellular polymer dissolution. The organics released from the pretreated sludge were more readily and rapidly consumed due the presence of abundant microorganisms. The US group was more capable of releasing contaminants than the NaOH group, while the US-NaOH group overrode both. The growth characteristics, photosynthetic performance, and effluent treatment properties of Chlorella were observed in all group. In the untreated group, Chlorella exhibited higher algal density, maximum photochemical quantum yield, and effluent treatment capacity. The results demonstrated that sludge pretreatment could facilitate the release and rapid consumption of pollutants. Additionally, the NaOH pretreatment could remove the refractory organics to a higher degree, and could also accumulate more photosynthetic pigments. This study demonstrated the feasibility of Chlorella being used in practical scenarios such as hydrolytic acidification solutions for different sludge treatment methods, providing data for wastewater treatment and resource utilization. [ABSTRACT FROM AUTHOR]

Background: Microalgal cultures are evolving into a promising ecofriendly technology for a host of applications. To be sustainable, culture conditions need to be optimized and then controlled. One way to develop robust controllers for a cultivation system is by using mathematical growth models to simulate microalga‐based production. In this scenario, engineering design tasks begin by selecting the critical variables of these models. Results: A new methodology for determining the significance ranking of a model's input factors under steady‐state operation (parameters (e.g. biological, geometrical) and/or process variables) was designed. The sensitivity of biomass response to its inputs was investigated in four different photobioreactor growth models within a nominal operational region. The methodology ranks models' input factors based on the one‐at‐a‐time Morris method of elementary effects and variance‐based Sobol's method. Such information provided by the presented procedure is valuable as it reveals which input parameters explain most of the variance in model predictions. Conclusion: The methodology allowed the identification of controlled variables and biological parameters to be targeted for enhanced calibration. Furthermore, the presented methodology showed that in continuous reactors the dilution rate is a critical variable of the process. Therefore, it should be controlled. Additionally, most surprisingly, it is observed that controlling the light intensity within the optimum point of operation is not necessarily a crucial task. However, although its manipulation is still important, the accurate calibration of the parameters of the model may represent a greater influence on the biomass response. © 2023 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

The reuse of the culture media after biomass growth can be a cost-effective strategy for large-scale microalgae production, especially when the target product is biofuel. Therefore, this study aimed to investigate the effect of recycling the microalgae Tetradesmus obliquus culture medium, focusing on the improved production of biomass and lipids, biodiesel properties, and cost reduction. The experiments were carried out in duplicate and three sequential steps with successive recycling (50% of the clarified medium and 50% of the standard). It was found that cells from recycled cultures had a similar overall performance as those from the fresh medium (standard). From this verification, the main findings of this research pointed out that (i) the consumption of the nutrients was efficient, with values in the order of 99% nitrate, 20% phosphate, 64% total iron, and 9% potassium; (ii) the average contents of biomass and lipids in the recycled medium increased around 20% to 24%, respectively, concerning the standard; (iii) the polyunsaturated fatty acids pool present in the microalgal oil dropped from 20.71 to 9.78% in the recycled culture, which represents a high-quality feedstock for biofuel; and (iv) the biodiesel properties evaluated, including iodine and saponification values, were 48 g I2 100 g−1 and 254 mg KOH/goil−1, respectively. Finally, this recyclability bioprocess can reduce overall costs by about 34%, thus improving the economic viability of microalgae production. [ABSTRACT FROM AUTHOR]

To achieve the sustainable and effective removal efficiency of nutrients in black odorous water, light source, inter-species microalgae mixed culture, and the harvesting effect were all explored. The results showed that under a LED light source, the addition of interspecific soluble algal products (SAP) promoted the growth of Haematococcus pluvialis (H. pluvialis) M1, and its maximum specific growth rate was 1.76 times that of H. pluvialis cultivated alone. That was due to the hormesis effect between the two kinds of microalgae, the SAP produced by Scenedesmus could stimulate the growth of H. pluvialis. The algae and bacteria symbiotic system with black odorous water as the medium showed excellent performance to treat nutrients, where the concentration of ammonia nitrogen (NH3-N) and total phosphorus (TP) (0.84, 0.23 mg/L) met the requirements of landscape water. The microbial diversity analysis revealed that the introduction of microalgae changed the dominant species of the bacterial community from Bacteroidota to Proteobacteria. Furthermore, timely microalgae harvesting could prevent water quality from deteriorating and was conducive to microalgae growth and resource recycling. The higher harvest efficiency (98.1%) of H. pluvialis was obtained when an inoculation size of 20% and 0.16 g/L FeCl3 were provided. [ABSTRACT FROM AUTHOR]

Waste-activated sludge disposal has now become a serious global problem. After pretreatment, sludge was hydrolyzed and acidified to release nutrients. The effects of different sludge pretreatments on microalgal growth and contaminants in a hydrolysis acidification solution were compared. Alkalinization (NaOH), ultrasound (US), and combined pretreatment techniques (US-NaOH) all promoted contaminants’ release from the sludge by triggering microbial cell wall rupture and extracellular polymer dissolution. The organics released from the pretreated sludge were more readily and rapidly consumed due the presence of abundant microorganisms. The US group was more capable of releasing contaminants than the NaOH group, while the US-NaOH group overrode both. The growth characteristics, photosynthetic performance, and effluent treatment properties of Chlorella were observed in all group. In the untreated group, Chlorella exhibited higher algal density, maximum photochemical quantum yield, and effluent treatment capacity. The results demonstrated that sludge pretreatment could facilitate the release and rapid consumption of pollutants. Additionally, the NaOH pretreatment could remove the refractory organics to a higher degree, and could also accumulate more photosynthetic pigments. This study demonstrated the feasibility of Chlorella being used in practical scenarios such as hydrolytic acidification solutions for different sludge treatment methods, providing data for wastewater treatment and resource utilization.

A correct assessment of microalgae growth on porous building materials (i.e.: fired bricks, sandstones and limestones) can provide a useful tool for researchers and practitioners. In fact, it may help predicting the biofouling damage extension and it can assist the experts in a correct planning of maintenance interventions to limit costs. The literature regarding such issue outlined the Avrami’s model as the most recurrent one, even considering the influence of biocidal treatments on the substrate. However, it seems to have some limitations when the growth is very fast or, conversely, when the latency time is extended over the time. Therefore, a different modelling approach is here proposed, by using the logistic function (extensively used i.e. in population growth). Results reveal that the logistic function seems to succeed in better modelling the available experimental data. Moreover, it seems to overcome the limits of the Avrami’s model, as well as to be less influenced by the main drivers of microalgae growth, such as porosity and roughness of the substrate, biocides treatments and environmental conditions (temperature). [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrochemical pretreatment reduced water use for dilution of swine wastewater. • Electrochemical pretreatment contributed to turbidity and TP removal from swine wastewater. • Electrochemical treatment mitigated negative impact of Zn2+ and Cu2+ on microalgae growth. • Coupling electrochemical pretreatment with S. obliquus cultivation improved nitrogen and phosphorus removal. This study integrates electrochemical pretreatment with microalgae (Scenedesmus obliquus) treatment to enhance nitrogen and phosphorus removal and resource recovery from swine wastewater. By optimizing electrochemical and microalgae treatment conditions, the dilution factor and the hydraulic retention time for microalgae treatment were reduced to 5 times and 7 days, respectively. Under the optimized operational conditions, removal efficiencies of total nitrogen and ammonia could reach over 89 % and 96 %, respectively, and the removal efficiency of total phosphorus was over 99 %. The study also found that aluminum was more suitable than iron for anode as it produced fewer residues. Additionally, the electrochemical pretreatment reduced Cu2+ and Zn2+ concentrations, mitigating negative impacts on microalgal growth. The microalgae biomass harvested from developed processes was rich in saturated fatty acids, which was desirable for biodiesel production. This approach addresses the challenges of nutrient removal for swine wastewater treatment with high quality biomass recovery. [ABSTRACT FROM AUTHOR]

• Single and combined effects of MPs and OA on P. purpureum were investigated. • 0.1 μm MPs significantly promoted algal growth at concentrations of 5–100 mg L−1. • 1 μm MPs caused negative effect on microalgae at medium and high concentrations. • Seawater acidification mitigated the impacts of MPs on microalgae. Microplastics (MPs) pollution and seawater acidification have increasingly become huge threats to the ocean ecosystem. Their impacts on microalgae are of great importance, since microalgae are the main primary producers and play a critical role in marine ecosystems. However, the impact of microplastics and acidification on unicellular red algae, which have a unique phycobiliprotein antenna system, remains unclear. Therefore, the impacts of polystyrene-MPs alone and the combined effects of MPs and seawater acidification on the typical unicellular marine red algae Porphyridium purpureum were investigated in the current study. The result showed that, under normal seawater condition, microalgae densities were increased by 17.75–41.67 % compared to the control when microalgae were exposed to small-sized MPs (0.1 μm) at concentrations of 5–100 mg L−1. In addition, the photosystem II and antioxidant enzyme system were not subjected to negative effects. The large-sized MPs (1 μm) boosted microalgae growth at a low concentration of MPs (5 mg L−1). However, it was observed that microalgae growth was significantly inhibited when MPs concentration increased up to 50 and 100 mg L−1, accompanied by the remarkably reduced F v /F m value and the elevated levels of SOD, CAT enzymes, phycoerythrin (PE), and extracellular polysaccharide (EPS). Compared to the normal seawater condition, microalgae densities were enhanced by 52.11–332.56 % under seawater acidification, depending on MPs sizes and concentrations, due to the formed CO 2 -enrichment condition and appropriate pH range. PE content in microalgal cells was significantly enhanced, but SOD and CAT activities as well as EPS content markedly decreased under acidification conditions. Overall, the impacts of seawater acidification were more pronounced than MPs impacts on microalgae growth and physiological responses. These findings will contribute to a substantial understanding of the effects of MPs on marine unicellular red microalgae, especially in future seawater acidification scenarios. [ABSTRACT FROM AUTHOR]

Featured Application: The virgin soil extracts have a huge potential as growth enhancers for the mass cultivation of microalgae. The microalgae-based industries are trending upwards, particularly as the feed ingredient for aquaculture. Therefore, a sustainable and reasonably priced source of nutrients to support the mass cultivation of microalgae is in great demand. The present study explored the feasibility of using extracts from virgin soil as natural growth-promoting nutrients for the cultivation of Nannochloropsis oculata, Nannochloropsis oceanica, and Chlorella sorokiniana. The extracts were obtained from Bera Lake Forest using five different treatment methods. The greatest retrieval of dissolved organic carbon, total dissolved nitrogen, and total dissolved phosphorus were observed with the autoclave treatment method at 121 °C twice, yielding a respective concentration of 336.56 mg/L, 13.40 mg/L, and 0.14 mg/L, respectively. The highest growth was recorded with Nannochloropsis oculata resulting in an optical density of 0.488 ± 0.009 (×103 cell mL−1), exhibiting 43% and 44% enhanced growth in comparison to Nannochloropsis oceanica and Chlorella sorokiniana, respectively. The specific growth rate (0.114 a ± 0.007 d−1) was the highest for Nannochloropsis oculata when the 24 h-extraction method was used, whereas the utilization of the autoclave 121 °C twice treatment method contributed to the highest specific growth of Nannochloropsis ocenica (0.069 a ± 0.003 d−1) and Chlorella sorokiniana (0.080 a ± 0.001 d−1). Collectively, these findings suggested that the addition of soil extracts which is sustainable and inexpensive promoted the growth of microalgae compared to the control system. A further study investigating the optimum culture conditions for enhanced microalgae growth will be carried out for the mass production of microalgae biomass. [ABSTRACT FROM AUTHOR]

Microcystis aeruginosa is a common microalgae in nature. It is also the dominant algae species to form freshwater blooms. Water bloom will do harm to water environment, so this paper studies the growth law of Microcystis aeruginosa. Single factor experiment and orthogonal experiment were carried out by changing the influencing factors such as photoperiod, initial dosage and initial pH. The results showed that within a certain range, the larger the photoperiod, the larger the initial dosage, the higher the initial pH, the better the growth of Microcystis aeruginosa and the greater the increase of pH value. This study is to deepen the understanding of the growth law of Microcystis aeruginosa. It provides a scientific basis for controlling the growth of Microcystis aeruginosa. [ABSTRACT FROM AUTHOR]

Iron and phosphorus (P) are the important micro- and macro-nutrient for microalgae growth, respectively. However, the effect of iron and P on microalgae growth in co-culture associating with the formation of dominate algae has not been investigated before. In the current study, Anabaene flos-aquae, Chlorella vulgaris and Melosira sp. were co-cultivated under the addition of different initial iron and P to reveal the effect of iron and phosphorus on the growth of microalgae. The results showed that the mean growth rate of A. flos-aquae, C. vulgaris and Melosira was 0.270, 0.261 and 0.062, respectively, indicating that the A. flos-aquae and C. vulgaris algae are liable to be the dominant algae while the growth of Melosira was restrained when co-cultured. The ratio of Fe to P has a significant impact on the growth of microalgae and could be regarded as an indicator of algae growth. Microalgae showed a much more obvious uptake of iron compared to that of P. The information obtained in the current study was useful for the forecast of water quality and the control of microalgae bloom. [ABSTRACT FROM AUTHOR]

The microalgae-based industries are trending upwards, particularly as the feed ingredient for aquaculture. Therefore, a sustainable and reasonably priced source of nutrients to support the mass cultivation of microalgae is in great demand. The present study explored the feasibility of using extracts from virgin soil as natural growth-promoting nutrients for the cultivation of Nannochloropsis oculata, Nannochloropsis oceanica, and Chlorella sorokiniana. The extracts were obtained from Bera Lake Forest using five different treatment methods. The greatest retrieval of dissolved organic carbon, total dissolved nitrogen, and total dissolved phosphorus were observed with the autoclave treatment method at 121 °C twice, yielding a respective concentration of 336.56 mg/L, 13.40 mg/L, and 0.14 mg/L, respectively. The highest growth was recorded with Nannochloropsis oculata resulting in an optical density of 0.488 ± 0.009 (×103 cell mL−1), exhibiting 43% and 44% enhanced growth in comparison to Nannochloropsis oceanica and Chlorella sorokiniana, respectively. The specific growth rate (0.114 a ± 0.007 d−1) was the highest for Nannochloropsis oculata when the 24 h-extraction method was used, whereas the utilization of the autoclave 121 °C twice treatment method contributed to the highest specific growth of Nannochloropsis ocenica (0.069 a ± 0.003 d−1) and Chlorella sorokiniana (0.080 a ± 0.001 d−1). Collectively, these findings suggested that the addition of soil extracts which is sustainable and inexpensive promoted the growth of microalgae compared to the control system. A further study investigating the optimum culture conditions for enhanced microalgae growth will be carried out for the mass production of microalgae biomass.

The influence of fish steroid hormones on algal (Scenedesmus quadricauda) physiology was investigated, as it is relevant to the use of fishery wastewaters for microalgae biomass production. S. quadricauda was exposed to two steroids, 17β-estradiol (E2) and 17,20,β-dihydroxy-4-pregnen-3-one (17,20β-P), commonly found in fish farm effluents. These hormones demonstrated stimulatory effects on S. quadricauda cell growth and accumulation of chlorophyll-a, total carotenoids, and lipids. Both steroids promoted total carotenoid accumulation to higher degree than they promoted chlorophyll accumulation. E2 was a more powerful inducer of the accumulation of total carotenoids and lipids compared with 17,20β-P. The work was conducted to evaluate the possibility of integrating cold-water fish farming with algae production to maximize nutrient recycling in aquaculture wastewaters. Our data suggest that nano-concentrations of fish sex hormones in aquaculture wastewaters could be used to enhance both algae biomass production and the synthesis of high-value molecules. • Scenedesmus quadricauda was exposed to two fish steroid hormones. • The fish steroid hormones stimulated S. quadricauda cell growth. • Accumulation of chlorophyll-a and total carotenoids were also stimulated. • The fish steroid hormones alternated lipid fatty acid profiles. • The steroids from fishery effluents are promising stimulants for biofuel production. [ABSTRACT FROM AUTHOR]

Recently, using microalgae to remediate heavy metal polluted water has been attained a huge attention. However, heavy metals are generally toxic to microalgae and consequently decrease biomass accumulation. To address this issue, the feasibility of adding exogenous glucose, employing algae-bacteria system and algae-bacteria-activated carbon consortium to enhance microalgae growth were evaluated. The result showed that Cd2+ removal efficiency was negatively correlated with microalgal specific growth rate. The exogenous glucose alleviated the heavy metal toxicity to algal cells and thus increased the microalgae growth rate. Among the different treatments, the algae-bacteria-activated carbon combination had the highest biomass concentration (1.15 g L−1) and lipid yield (334.97 mg L−1), which were respectively 3.03 times of biomass (0.38 g L−1) and 4.92 times of lipid yield (68.08 mg L−1) in the single microalgae treatment system. Additionally, this algae-bacteria-activated carbon consortium remained a high Cd2+ removal efficiency (91.61%). In all, the present study developed an approach that had a great potential in simultaneous heavy metal wastewater treatment and microalgal lipid production. [Display omitted] • Biosorption capability of algae was inversely proportional to specific growth rate. • Exogenous glucose increased C. pyrenoidosa growth under Cd stress. • Algae-bacteria-activated carbon consortium showed the highest biomass and lipid yield. • More than 90% Cd2+ removed by algae-bacteria-activated carbon consortium. [ABSTRACT FROM AUTHOR]

Rain affects the building envelope's durability, increasing the amount of water available on the surfaces due to the wind pressure. Water can activate and accelerate chemical and biological processes causing algae and cyanobacteria growth. The velocity of this process depends on several parameters, such as temperature, relative humidity (RH%), surface characteristics (i.e. roughness, porosity) and water availability on the building surfaces considering that algae and cyanobacteria fall into a latent state without water. Wind plays a significant role: it can push the rain against the facades, wetting them and increasing the growth speed. This paper analyzes the impact of rain on algae growth on building facades, considering wind influence, through a neural network (NN). Experimental data collected imposing different combinations of temperature, RH% and water availability on the surface, also due to rain and WDR, of 5 different porous materials (bricks) were used to train and test the NN. The NN was tested showing an accuracy of 82% (r-squared) in predicting algae growth concerning experimental data, based on the imposed parameters: wind speed, wind direction; air temperature; RH%; surface characteristics (porosity, roughness). Three different UE locations, characteristics of different Koppen-Geiger climates, and four different exposures for each location were selected. The application of the trained NN in different climates, considering different orientations, demonstrates that WDR is the main factor affecting microalgae growth. WDR can increase by more than two times the area covered by algae in a year, depending on the climate and the orientation. • A neural network has been implemented to predict microalgae growth on the building facade. • Rain and wind have been included in the model for the first time. • The model has been applied to 3 representative locations of the main UE Koppen-Geiger climates. • Rain can increase from 2 to 3 times the microalgae growth speed. • Temperatures affect the microalgae growth, reducing the velocity of the microalgae surface coverage ratio. [ABSTRACT FROM AUTHOR]

Due to its abundance and also flexibility of cultivation conditions, Chlorella vulgaris microalgae is one of the most ideal options available in order to production of microalgae based biodiesel. Since vulgaris cultivation for fuel production needs economic considerations to be taken, and in first place providing biomass and lipid production costs is important, wide researches have been conducted in this field, and this study aims to spot the best condition for cultivation of this valuable specie by reviewing the whole research conducted. So far, Researchers' efforts show that, the best condition for vulgaris cultivation is mixotrophic regime which is done in a bubble column photobioreactor. Glucose as carbonic source and nitrate as nitrogen source, have the most efficacy among nutrition conditions. It is known the best results obtain in amounts glucose and nitrate of 20 and o.5 g/L respectively. Alkaline medium (pH 9 to 10), non-continuous illumination, 5 to 7 Klux and a 200 mL/min aeration flow rate, indicated the best physical conditions. The most vulgaris biomass amount produced was 3.43 g/L, and the best lipid productivity was measured 66.25 mg/L/day.

This study investigated the growth-dependent role of algal organic matters (AOMs) to achieve high removal efficiency (R.E) of microalgae. The results showed that the microalgae cells produced 96 ± 2% of total AOMs as loose bound AOMSS (LB-AOMs) and 4 ± 1% as cell-bound (CB-AOMs) in exponential phase. In stationary phase, LB-AOMs and CB-AOMs were 46 ± 0.7percentage and 54 ± 0.2 percentage, respectively. The R.Es in exponential and stationary phase were 83 ± 2.6% and 66 ± 1.2%, respectively. It is found that the difference of biomass concentration (between exponential and stationary phase) had no significant impact on the R.E (P > 0.01). Further investigations revealed that LB-AOMs inhibit flocculation in exponential and CB-AOMs in stationary phase; however, CB-AOMs showed stronger inhibition than the LB-AOMs (P < 0.01). The provision of calcium (17 ± 0.9 mg/L) to the culture reduced the AOMs inhibition and improved the R.E from 66 ± 1.2% (in control) to 90 ± 4.2%. An increase in R.E was attributed to the interaction of calcium with AOMs and subsequently acting as a flocculant. The findings of this study can be valuable to improve the performance of auto-flocculation technology, which is mainly limited by the presence of AOMs. [ABSTRACT FROM AUTHOR]

As a necessary micronutrient for algal growth, iron (Fe) has important effects on the physiological metabolism and enzymatic reactions of algae. In this study, a series of experiments were designed to compare the effects of different kinds of iron on the growth of Anabaena flos-aquae. Results showed that the promotion of iron species on algae growth was in order of ferric ammonium citrate > EDTA-Fe > iron ions > iron oxalate. When the concentration of iron is in the range of 0.1–0.8 mg/L, iron species have more significant influences on Anabaena bloom compared with iron concentration. Our experiments also revealed that A. flos-aquae has the strongest adsorption capacity for iron ion among the four iron sources and further induced. This leads to the toxicity of the iron ion group to algal cells at low concentration. [ABSTRACT FROM AUTHOR]

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Microalgal biomass has received much attention as feedstock for biofuel production due to its capacity to accumulate a substantial amount of biocomponents (including lipid, carbohydrate, and protein), high growth rate, and environmental benefit. However, commercial realization of microalgal biofuel is a challenge due to its low biomass production and insufficient technology for complete utilization of biomass. Recently, advanced strategies have been explored to overcome the challenges of conventional approaches and to achieve maximum possible outcomes in terms of growth. These strategies include a combination of stress factors; co-culturing with other microorganisms; and addition of salts, flue gases, and phytohormones. This review summarizes the recent progress in the application of single and combined abiotic stress conditions to stimulate microalgal growth and its biocomponents. An innovative schematic model is presented of the biomass-energy conversion pathway that proposes the transformation of all potential biocomponents of microalgae into biofuels. [ABSTRACT FROM AUTHOR]

Although intensive marine fish farming is often assumed to be eco-friendly, the associated activity can lead to chronic exposure of marine organisms to potentially toxic discharges. Moreover, despite the increasing popularity of integrated multi-trophic aquaculture (IMTA), studies of the effects of fish farm effluents are almost non-existent. In the present study, the changes in the toxic potential of effluents from five land-based marine fish farms in NW Spain subjected for different lengths of time to a biodegradation procedure (for 0, 48, 120, and 240 h) were assessed in a battery of bioassays including organisms from different trophic levels (Vibrio fischeri, Isochrysis galbana, and Paracentrotus lividus). The results of the bioassays at the different times were then considered together with farm water flow in the Potential Ecotoxic Effects Probe (PEEP) index. Despite the high volumes of effluents discharged, the generally low toxicity of the effluents hinders assessment of potentially toxic effects. However, dose-response curves and statistical analysis demonstrated the existence of toxic effects during the first five days of the biodegradation procedure, especially immediately after sampling. The proposed modification of the PEEP index better reflects the changes in toxicity over time.ᅟ [ABSTRACT FROM AUTHOR]

Microalgae in genus Chlorella and Scenedesmus are common in aquatic ecosystems and are widely used for various studies on algal growth and applications. Macroalgae may play an important role for control of microalgal growth, attributable to their rich content of bioactive compounds. In this study, the brown seaweed Ascophyllum nodosum was extracted with 70% acetone and the extract was used to treat the green microalgae, Chlorella vulgaris and Scenedesmus sp. Cell density and chlorophyll a concentration were used as growth indexes to evaluate the effects of A. nodosum extract (ANE) on the microalgae. The ANE with concentrations > 1% exhibited significant capability of inhibition of the growth of microalgae by over 80%. On the contrary, 1% ANE caused varying degrees of acceleration of cell proliferation and chlorophyll a synthesis in C. vulgaris and Scenedesmus sp., respectively. Analysis of antioxidant activities of the enzymes superoxide dismutase (SOD) and catalase (CAT) revealed the impact of ANE on the antioxidant defense system of the microalgae. The SOD and CAT activities were significantly depressed by high concentrations (> 2%) ANE, while a slight increase of the enzyme activities was observed with 1% ANE at the early period, which could be correlated to the growth response. Therefore, the mechanism of microalgae control could be related to the interaction between the ANE and the antioxidant defense systems. Phlorotannins are proposed as the principal algistatic components in the ANE which could be utilized in controlling microalgae growth. [ABSTRACT FROM AUTHOR]

Abstract Current study investigated the effectiveness of different macrophytes as culture media for Ankistrodesmus gracilis in laboratory conditions. Significant difference (p < 0.05) was reported in cell density with regard to conventional culture medium (CHU12) and macrophytes culture media. Mean cell density in NPK, Eichhornia crassipes and E. azurea media was higher (p < 0.05) than in conventional culture medium. Chlorophyll-a was higher than 1 g.L-1, except in CHU12 (0.7 ± 0.4 g.L-1) and T. domingensis (0.8 ± 0.3 g.L-1) media. Nitrate decreased sharply as from the 7th-day of the experiment. Ammonium and total phosphorus were highest in culture media and ranged between 0.4 g.L-1 (P. cordata medium) and 1.7 g.L-1 (CHU12 medium) for ammonium, and between 0.8 g.L-1 (CHU12 medium) and 1.9 g.L-1 (T. domingensis medium) for total phosphorus. Results revealed inorganic fertilizer and macrophytes combined with vitamins may be effective as culture media and strongly supports the growth of Ankistrodesmus gracilis, since cell density and biochemical composition are similar to or higher than conventional culture medium (CHU12). Macrophyte is a tool for aquaculture since biological wastes may be used with nutrients to improve the cultivation of microalgae.

Several factors have the potential to influence microalgae growth. In the present study, nitrogen concentration and light intensity were evaluated in order to obtain high biomass production and high phycoerythrin accumulation from Porphyridium purpureum. The range of nitrogen concentrations evaluated in the culture medium was 0.075−0.450 g L−1 and light intensities ranged between 30 and 100 μmol m−2 s−1. Surprisingly, low nitrogen concentration and high light intensity resulted in high biomass yield and phycoerythrin accumulation. Thus, the best biomass productivity (0.386 g L−1 d−1) and biomass yield (5.403 g L−1) were achieved with NaNO3 at 0.075 g L−1 and 100 μmol m−2 s−1. In addition, phycoerythrin production was improved to obtain a concentration of 14.66 mg L−1 (2.71 mg g−1 of phycoerythrin over dry weight). The results of the present study indicate that it is possible to significantly improve biomass and pigment production in Porphyridium purpureum by limiting nitrogen concentration and light intensity.

Nanosized titanium dioxide (nTiO 2 ) is widespread in many commercial products and several authors investigated its ecotoxicity effects focusing mainly on freshwater environments. Data on saltwater species are still lacking or present contradicting results. We compared for the first time the toxicity of TiCl 4 and nTiO 2 considering standard toxicity tests with microalgae Phaeodactylum tricornutum (growth inhibition test, 1.8–90 mg/L) and crustacean Artemia franciscana (mortality test, 0.5–64 mg/L). For A. franciscana , two alternative scenarios were considered beside standard protocol: i) darkness; and ii) starvation. About microalgae, results evidenced that effects of TiCl 4 (EC50 = 63 mg/L) were greater than nTiO 2 (no EC50), but IC10 and IC20 were significantly lower suggesting that nTiO 2 is more harmful than TiCl 4 at lower concentrations. The effects of TiCl 4 to crustaceans larvae in all exposure scenarios were lower compared to nTiO 2 (EC50(96 h) = 15 mg/L - standard protocol). During toxicity testing, the absence of light generally lowered nTiO 2 effects while starvation increased the toxicity of both TiCl 4 and nTiO 2 . [ABSTRACT FROM AUTHOR]

Microalgae represent a promising feedstock for the sustainable production of biofuels and many other bio-commodities. However, the optimization of their productivity by assessing the impact that several environmental factors have on microalgae growth still requires intense investigation, as well as numerous and time consuming experiments. In this scenario, microscale technologies are emerging as a valuable tool to improve data production and accordingly to speed up the optimization process, while maintaining a high experimental reliability. Using these approaches for microalgae present additional challenges because of the necessity of dealing with light as a source of energy to support cell metabolism. Currently developed microscale platforms are complex, often requiring a deep experience in the microfluidic field to monitor the device functionality. To overcome this drawback while keeping microscale benefits, here we describe the use of a simple and flexible micro-photobioreactor (micro-PBR) coupled with a quick and reliable growth evaluation method. The system is demonstrated to sustain optimal growth of Nannochloropsis gaditana cells, allowing to assess the impact of different light intensities and to monitor the cells photosynthetic functionality by measuring chlorophyll (Chl) fluorescence in vivo , while providing for a significant time reduction when compared to traditional experimental approaches. [ABSTRACT FROM AUTHOR]

Antibiotics are increasingly being used in human and veterinary medicine, as well as pest control in agriculture. Recently, their emergence in the aquatic environment has become a global concern. The aim of this study was to evaluate the effect of streptomycin on growth and photosynthetic activity of Chlorella vulgaris after 72 h exposure. We found that growth, photosynthetic activity and the content of the D1 protein of photosystem II decreased. Analysis of chlorophyll a fluorescence emission shows a reduction in the energy transfer between the antenna complex and reaction center. Also the activity of the oxygen evolution complex and electron flow between Q A and Q B were significantly reduced; in contrast, we found an increase in the reduction rate of the acceptor side of photosystem I. The foregoing can be attributed to the inhibition of the synthesis of the D1 protein and perhaps other coded chloroplast proteins that are part of the electron transport chain which are essential for the transformation of solar energy in the photosystems. We conclude that micromolar concentrations of streptomycin can affect growth and photosynthetic activity of Chlorella vulgaris . The accumulation of antibiotics in the environment can become an ecological problem for primary producers in the aquatic environment. [ABSTRACT FROM AUTHOR]

Microalgae have a substantial potential as a renewable energy resource, but sustainable microalgae-based bioenergy production has to find an inexpensive water and nutrient resource. Wastewater has been considered as such a resource to reduce environmental impacts and economic burdens of microalgae cultivation. Understanding of microalgae growth kinetics in wastewater is necessary to improve microalgae productivity for successful implementation of the integrated microalgae-wastewater system. This study presents an integrated co-limitation kinetic model of microalgae growth in anaerobically digested municipal sludge centrate. Nitrogen (N), dissolved carbon dioxide (CO 2 ) concentrations, light intensity (I), and temperature (T) were selected as major growth factors in the model. The model framework was constructed by combining threshold and multiplicative structures to explain the relationship among these factors. Depending on culture conditions, the integrated model consists of alternative rate expressions for factors selected. These expressions include the Andrews and Monod models for both CO 2 and N, and the Chalker and Muller-Fuega models combined with the Arrhenius equation for light intensity and temperature. The model was calibrated and validated using batch studies with anaerobically digested municipal sludge centrate as wastewater source. Criteria to select the rate expressions considering limitation conditions include NH 4 -N ≤ 150 mg L − 1 , aqueous CO 2 ≤ 50 mg L − 1 , and light intensity ≤ 90 μmol photon m − 2 s − 1 . Above these ranges, the rate expressions considering both limitation and inhibition were applied to the model. The model was shown to have a reasonable growth rate prediction of Chlorella sp. under different nutrient levels of the centrate. [ABSTRACT FROM AUTHOR]