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The thermodynamic instability of conventional aqueous foam‐stabilized surfactants is a critical bottleneck in the construction of porous materials. Herein, a novel strategy is proposed for preparing a capillary foam based on Chlorella and utilizing it as a template for constructing porous materials with high‐efficiency adsorption. The capillary foam was stabilized by Chlorella particles enclosed within a gel network of oil bridges connecting the particles (capillary suspension). Chlorella particles, which act as stable particles, form oil bridges and are distributed at the phase interface of the capillary foam. These particles exhibited resistance to shear forces, allowing the formation of a long‐term stable capillary foam. Using this foam as a template, a porous material with outstanding adsorption performance for Methylene Blue (MB) and Brilliant Green (BG) dyes was successfully constructed. Additionally, the material exhibited a sustained high adsorption performance even after five thermal regeneration‐adsorption cycles. In conclusion, this study presents a green and straightforward method for constructing capillary foams with high stability, which is a promising approach for developing porous materials with exceptional adsorption and regeneration properties for dyes. [ABSTRACT FROM AUTHOR]

The present study reports a new representative of Chlorella‐clade that was newly isolated from the Lake Vos'merka (Samara region, Russian Federation). 18S–ITS1–5.8S–ITS2 sequence analyses indicated that the studied strain ACSSI 368 and related Chlorella chlorelloides, Chlorella pulchelloides, formed an separate cluster in the Chlorella‐clade, unrelated to the holotype of the genus Chlorella – Chlorella vulgaris. The independent place of the genus was also confirmed by genetic distances. The individual species status of the studied strain ACSSI 368, compared with the sister C. chlorelloides, was confirmed by morphological differences (cell number per colony, type of chloroplast, number of autospores), genetic distances of the interspecific level by 18S–ITS1–5.8S–ITS2 fragment, alone by internal transcribed spacer 1 (ITS1) and internal transcribed spacer 2 (ITS2) sequences, one complementary base change in ITS1, and the results of species delimitation using five methods. A description of studied strain ACSSI 368 was provided as an authentic strain of the type species Aliichlorella ignota. Currently, the new genus Aliichlorella also includes Aliichlorella chlorelloides comb. nov. and Aliichlorella pulchelloides comb. nov. In general, six different delimitation algorithms were used in the present study. The ASAP (i.e. assemble species by automatic partitioning) and LocMin (i.e. 'local minimum' function) algorithms showed synchronous results, but their accuracy with respect to closely related species was somewhat lower. The mlPTP algorithm simultaneously aimed to combine closely related species in one and at the same time divide slightly distinguishing strains within a species into several molecular operational taxonomic units. The bPTP algorithm separated excessively Chlorella‐clade representatives into individual species. The generalized mixed Yule coalescent (GMYC) algorithm results were consistent the most with the modern understanding of the Chlorella‐clade taxonomy. However, the same method is one of the most time‐consuming because, for its implementation, it is necessary to carry out long preparatory work. The KoT results were less accurate than the GMYC results, although this is less time‐consuming because it does not require the preliminary construction of ultrametric trees. [ABSTRACT FROM AUTHOR]

Summary: The production of alkaliphilic microalgae can contribute to address the challenging cost of using pure carbon dioxide in large reactors. At high pH values, carbon dioxide is rapidly scavenged and the supply rates of dissolved inorganic carbon from the atmosphere to alkaline media are high. The present study aimed to identify microalgal strains that can cope with high alkalinity and aeration rates. Eight strains were studied and the microalgae Chlorella vulgaris, Scenedesmus almeriensis and Nannochloropsis gaditana were the only ones that were able to grow under these conditions. Their biomass productivities using laboratory‐scale bubble columns with no pH control and high aeration flow were 0.20 ± 0.03, 0.24 ± 0.03 and 0.08 ± 0.01 g·L−1·day−1, respectively. The production of the two former was scaled up to pilot‐scale bubble columns. Overall, the amount of atmospheric carbon dioxide that was transformed into biomass was in the range of 10%–30%, depending on the strain used and the photobioreactor setup. The biomass was rich in proteins and β‐carotene, both valuable products, highlighting the potential production of food ingredients while capturing carbon dioxide from the atmosphere. [ABSTRACT FROM AUTHOR]

Host–parasite interactions can cause strong demographic fluctuations accompanied by selective sweeps of resistance/infectivity alleles. Both demographic bottlenecks and frequent sweeps are expected to reduce the amount of segregating genetic variation and therefore might constrain adaptation during co‐evolution. Recent studies, however, suggest that the interaction of demographic and selective processes is a key component of co‐evolutionary dynamics and may rather positively affect levels of genetic diversity available for adaptation. Here, we provide direct experimental testing of this hypothesis by disentangling the effects of demography, selection and their interaction in an experimental host–parasite system. We grew 12 populations of a unicellular, asexually reproducing algae (Chlorella variabilis) that experienced either growth followed by constant population sizes (three populations), demographic fluctuations (three populations), selection induced by exposure to a virus (three populations), or demographic fluctuations together with virus‐induced selection (three populations). After 50 days (~50 generations), we conducted whole‐genome sequencing of each algal host population. We observed more genetic diversity in populations that jointly experienced selection and demographic fluctuations than in populations where these processes were experimentally separated. In addition, in those three populations that jointly experienced selection and demographic fluctuations, experimentally measured diversity exceeds expected values of diversity that account for the cultures' population sizes. Our results suggest that eco‐evolutionary feedbacks can positively affect genetic diversity and provide the necessary empirical measures to guide further improvements of theoretical models of adaptation during host–parasite co‐evolution. [ABSTRACT FROM AUTHOR]

Metallurgical slag such as solid waste generated in the steel industry carries environmental pollution risks, but it is rich in nutrients required by microalgae. Metallurgical slag used for carbon capture and biomass energy conversion has multiple benefits: (i) reduction and harmless treatment of metallurgical solid waste, (ii) assisting in carbon neutrality by efficient carbon fixation, and (iii) production of biodiesel from CO2. In this study, AOD, BOF, BFS, HVS, and VTS slag were applied to culture Chlorella pyrenoidosa (C. pyrenoidosa) with the regulation of growth, carbon fixation, and lipid synthesis. An excellent fixed amount of CO2 with 94.59 mg is obtained from C. pyrenoidosa biomass at BOF slag added (mass ratio of CO2 captured/microalgae/slag with 1.99/1.00/10.53) since high Ca/Mg mass ratio of 419 (8.38 mg/L Ca and 0.02 mg/L Mg), no Cr and low concentration of Al (0.04 mg/L) contribute to regulating antioxidant enzyme activity (SOD and POD) to resist ROS and improving PEPC activity to reduce carbon flux toward lipid to promote biomass synthesis. Both metal concentrations from Ca (5.86 mg/L), Mg (0.05 mg/L), Al (0.42 mg/L), and Cr (0.006 mg/L) and suitable pH (10.53) in AOD leaching solution at solid/liquid ratio of 0.5 g/L change carbon flow toward efficient lipid synthesis (47.07 wt%) by continuously providing raw materials and energy by regulating ACC, ME, and PEPC activities. High value‐added biodiesel with high concentrations of C16 and C18 methyl esters from lipid of C. pyrenoidosa is achieved, following other ecological and economic benefits including 197 mg CO2 captured and 2198 mg AOD applied with harmless. In this study, C. pyrenoidosa is cultured with elements from metallurgical slag solid waste, which promotes C. pyrenoidosa efficient carbon fixation to assist in carbon neutrality, and provides guidance for CO2 conversion to high‐value‐added products with low cost. [ABSTRACT FROM AUTHOR]

The microalga Chlorella pyrenoidosa is cultivated extensively for its constituents, which are of significant economic worth. Large‐scale growth of C. pyrenoidosa in outdoor environments is subject to various stressors such as elevated temperature. The purpose of this study was to assess the protective effects of exogenous 24‐epibrassinolide (EBL) on C. pyrenoidosa under high‐temperature conditions. Compared to a temperature of 30°C, increasing the temperature to 43°C reduced the enzymatic capacity for carbon assimilation and resulted in the buildup of reactive oxygen species (ROS), thus reducing photosynthesis and proliferation. It was observed that exogenous EBL protected C. pyrenoidosa cells against high temperatures, with an optimal EBL concentration of 100 nM, resulting in enhanced capacity for photosynthetic carbon assimilation with a notable reduction in the imbalance between the absorption of light and energy used under high‐temperature conditions. The addition of 100 nM EBL resulted in a 25.4% increase in cell density when exposed to elevated temperatures for 7 days. In addition, exogenous EBL reduced ROS production and increased the activities of critical antioxidant enzymes. This, in turn, mitigated heat‐induced oxidative damage, resulting in advantageous outcomes in terms of cellular development and maintenance. [ABSTRACT FROM AUTHOR]

This trial aimed to customize pikeperch (Sander lucioperca) larval nutrition using live feed enrichments based on Chlorella vulgaris and Trachydiscus minutus. Pikeperch larvae were fed with rotifers and Artemia enriched with C. vulgaris and T. minutus during the first 17 days after exogenous feeding (started 4 days post‐hatching [dph]) and only Artemia until 20 dph. Larvae were exposed to seven different enrichments: (a) Nannochloropsis occulata (Nanno 3600 reed Mariculture) (Control), (b) C. vulgaris cultured at 20°C in BG‐117 medium (BG20), (c) C. vulgaris cultured at 30°C in BG‐117 medium (BG30), (d) T. minutus cultured at 15°C (T15), (e) T. minutus cultured at 25°C (T25), (f) C. vulgaris cultured at 20°C in urea medium (U20), and (g) C. vulgaris cultured at 30°C in urea medium (U30). After 20 days, no significant differences were found between treatments on total length, standard length, myomere height, and eye diameter. On the contrary, significant differences were found in larval fatty acid composition after the trial period. Larvae from the BG30 treatment showed a significantly higher concentration of docosahexaenoic acid (5.61%), and larvae from the T25 treatment had a higher concentration of eicosapentaenoic acid 12.95%. Furthermore, larvae from the U20 treatment had a significantly higher arachidonic acid concentration of 0.116%. Overall, regarding essential fatty acid concentration, a significant difference was observed between the control treatment (Nannochloropsis) and the other treatments. No adverse effects were found on growth or survival when Nannochloropsis‐enriched live feed was replaced with the other enrichments. This trial's results will help optimize the pikeperch larvae's nutritional requirements and diversify the live feed enrichments used during the first feeding. [ABSTRACT FROM AUTHOR]

Chlorella pyrenoidosa has been grown in artificial vinasse digestate. The method being used is intended to gather data on kinetic parameters that govern the performance of C. pyrenoidosa cultivated in a medium containing bacterial components. This condition was developed by introducing 1000 μL of Bacillus cereus to the medium (5 ppm of vinasse: 15 ppm of NaHCO3 = 3:2), which was subsequently mixed with C. pyrenoidosa culture at a 1:1 v/v ratio. The cultivation was carried out in batch mode for 15 days. The photosynthesis process of C. pyrenoidosa was conducted in 14 h and supported by 2 mL L−1 Guillard, which was given every 5 days. The study additionally investigated how different amounts of Zeolite (30, 60, and 90 gL−1) affected the kinetic parameters of microalgae grown in artificial vinasse digestate. This study demonstrated that the utilization of artificial vinasse digestate as a growing medium for C. pyrenoidosa resulted in growth limitation symptoms of microalgae, as a consequence of unfavorable interaction between C. pyrenoidosa and bacteria that already existed in the medium. This is indicated by low values of growth kinetics parameters, including specific growth rate (0.0259 d−1) and biomass productivity (0.51774 gL−1d−1) as compared to the reactor without bacteria in the medium. Therefore, adding a certain quantity of Zeolite to the reactor is a promising alternative for mitigating the negative effects of bacterial presence. With the addition of 90 g L−1 of Zeolite to the reactor, the specific growth rate of C. pyrenoidosa increases by 71%, indicating an appropriate growth. In addition, the total yield of PHB formation and the Melanoidin degradation efficacy of this reactor improved by 70% and 98%, respectively. [ABSTRACT FROM AUTHOR]

Summary: Chlorella ohadii was isolated from desert biological soil crusts, one of the harshest habitats on Earth, and is emerging as an exciting new green model for studying growth, photosynthesis and metabolism under a wide range of conditions.Here, we compared the genome of C. ohadii, the fastest growing alga on record, to that of other green algae, to reveal the genomic imprints empowering its unparalleled growth rate and resistance to various stressors, including extreme illumination. This included the genome of its close relative, but slower growing and photodamage sensitive, C. sorokiniana UTEX 1663.A larger number of ribosome‐encoding genes, high intron abundance, increased codon bias and unique genes potentially involved in metabolic flexibility and resistance to photodamage are all consistent with the faster growth of C. ohadii. Some of these characteristics highlight general trends in Chlorophyta and Chlorella spp. evolution, and others open new broad avenues for mechanistic exploration of their relationship with growth.This work entails a unique case study for the genomic adaptations and costs of exceptionally fast growth and sheds light on the genomic signatures of fast growth in photosynthetic cells. It also provides an important resource for future studies leveraging the unique properties of C. ohadii for photosynthesis and stress response research alongside their utilization for synthetic biology and biotechnology aims. [ABSTRACT FROM AUTHOR]

Pregnancy dramatically changes maternal metabolism and the microbiome. Low‐grade inflammation can cause maternal complications and fetal abnormalities. The objective of this open‐label, randomized, controlled study was to evaluate the efficacy and safety of orally administered Chlorella, a green alga that is commercially available as a dietary supplement with rich nutrients and dietary fiber for pregnant women with low‐grade inflammation. Patients with C‐reactive protein levels >0.05 mg/dL (16 weeks gestation, n = 22) were enrolled and randomly allocated to the Chlorella group (n = 10) or control group (n = 12). We conducted blood biochemical tests at 25, 30, and 35 weeks gestation and evaluated the evacuation status (symptoms depending on the Rome IV C2 criteria and laxative usage), side effects, and complications throughout the investigation. We also monitored the status of the offspring. The Chlorella group (n = 0) showed a significantly lower rate of constipation than the control group (n = 8). This study demonstrated the beneficial effects and safety of Chlorella supplementation in pregnant women, which prevented constipation and unnecessary laxative administration. Chlorella dietary supplements contain essential amino acids and chlorophyll as well as minerals, such as iron, vitamins and fiber. Chlorella supplementation in pregnant patients with low‐grade inflammation was safe and decreased the prevalence of constipation. [ABSTRACT FROM AUTHOR]

Desert algae are important components of the desert soil crust and play an essential role in desert soil ecosystem development. Owing to their special habitat, desert algae are often exposed to harsh environments, among which drought represents the most common stress. Green algae are considered to have drought tolerance potential; however, only a few studies have investigated this. In this study, we selected the green alga Chlorella sp., which was isolated from desert soil, and studied its physiological response to polyethylene glycol (PEG) 6000‐induced drought stress. The results showed that drought stress can affect the photosynthetic efficiency of Chlorella sp., reduce its water retention ability, and destroy its ultrastructure. However, Chlorella sp. can cope with drought stress through a series of physiological regulatory strategies. Protective strategies include quick recovery of photosynthetic efficiency and increased chlorophyll content. In addition, induced synthesis of soluble proteins, lipids, and extracellular polysaccharide (EPS), and accumulation of osmotic regulatory substances, such as sucrose and trehalose, also contribute to improving drought tolerance in Chlorella sp. This study provides insights into the physiological responses of Chlorella sp. to drought stress, which may be valuable for understanding the underlying drought adaptation mechanisms of desert green algae. [ABSTRACT FROM AUTHOR]

Algae have been explored for renewable energy, nutraceuticals, and value‐added products. However, low lipid yield is a significant impediment to its commercial viability. Genetic engineering can improve the fatty acid profile of algae without compromising its growth. This study introduced the diacylglycerol acyltransferase (BnDGAT) gene from Brassica napus into Chlorella sorokiniana‐I, a fast‐growing and thermotolerant natural strain isolated from wastewater, which increased its intracellular lipid accumulation. Hygromycin‐resistant cells were selected, and enhanced green florescence protein fluorescence was used to distinguish pure transgenic cell lines from mixed cultures. Compared to the wild type, BnDGAT expression in transgenic C. sorokiniana‐I caused a threefold increase in non‐polar lipid and a twofold increase in polyunsaturated fatty acids. Nile red staining reaffirmed the presence of higher intracellular lipid bodies in transgenic cells. There was a substantial alteration in the fatty acid profile of transgenic alga expressing BnDGAT. The non‐essential omega 9 (C18: 1) fatty acid decreased (5%–7% from 18%), while alpha‐linolenic acid, an essential omega 3 fatty acid (C18: 3), was increased (23%–24% from 11%). This study substantiates a valuable strategy for enhancing essential omega‐3 fatty acids and neutral lipids to improve its nutritional value for animal feed. The increased lipid productivity should reduce the cost of producing fatty acid methyl esters (FAME). Improved FAME quality should address the clouding issues in cold regions. [ABSTRACT FROM AUTHOR]

Hydrothermal liquefaction (HTL) is the direct conversion of wet biomass into bio‐oil at high temperature (200–400°C) and high pressure (10–25 MPa). In this work, we investigated HTL with 4.5 g of Chlorella and 45 ml of water/ethanol (1:1 vol. ratio) in a 100 ml reactor. Bio‐oils produced are characterized via elemental analysis, thermogravimetric analysis, and gas chromatography–mass spectrometry (GC–MS). HTL of Chlorella was investigated at 240 and 250°C for 0 and 15 min under an air or H2 atmosphere and with and without 5% zeolite Y. Temperature increased the bio‐oil yield from 38.75% at 240°C to 43.04% at 250°C for 15 min reaction time. Longer reaction time increased the bio‐oil yield at 250°C from 39.14% for 0 min to 43.04% for 15 min. The H2 atmosphere had a significant effect for HTL at 240°C. Zeolite Y increased the bio‐oil yield significantly from 32.03% to 43.06% at 250°C for 0 min. The carbon content of bio‐oil increased with the temperature while the oxygen content decreased. The boiling point distribution of bio‐oils in the range of 110–300°C varies with temperature, and atmosphere. At 240°C for 15 min, the 110–300°C range increased from 31.19% in air (240‐15‐air) to 39.25% in H2 (240‐15‐H2). The H2 atmosphere increased the content of hydrocarbons, alcohols, and esters from 69.61% in air (240‐0‐air) to 82.83% in H2 (240‐0‐H2). Overall, temperature, reaction time, atmosphere, and catalyst all significantly influenced the yield and/or quality of bio‐oils from HTL of Chlorella. [ABSTRACT FROM AUTHOR]

Engineering living microorganisms to enhance green biomanufacturing for the development of sustainable and carbon‐neutral energy strategies has attracted the interest of researchers from a wide range of scientific communities. In this study, we develop a method to achieve photosynthesis‐mediated biomineralization of gold nanoparticles (AuNPs) inside Chlorella cells, where the photosynthesis‐dominated reduction of Au3+ to Au0 allows the formed AuNPs to locate preferentially around the thylakoid membrane domain. In particular, we reveal that the electrons generated by the localized surface plasmon resonance of AuNPs could greatly augment hypoxic photosynthesis, which then promotes the generation and transferring of photoelectrons throughout the photosynthetic chain for augmented hydrogen production under sunlight. We demonstrate that the electrons from AuNPs could be directly transferred to hydrogenase, giving rise to an 8.3‐fold enhancement of Chlorella cells hydrogen production independent of the cellular photosynthetic process under monochromatic 560 nm light irradiation. Overall, the photosynthesis‐mediated intracellular biomineralization of AuNPs could contribute to a novel paradigm for functionalizing Chlorella cells to augment biomanufacturing. [ABSTRACT FROM AUTHOR]

SUMMARY: While light is the driving force of photosynthesis, excessive light can be harmful. Photoinhibition is one of the key processes that limit photosynthetic productivity. A well‐defined mechanism that protects from photoinhibition has been described. Chlorella ohadii is a green micro‐alga, isolated from biological desert soil crusts, which thrives under extreme high light (HL). Here, we show that this alga evolved unique protection mechanisms distinct from those of the green alga Chlamydomonas reinhardtii or plants. When grown under extreme HL, a drastic reduction in the size of light harvesting antennae occurs, resulting in the presence of core photosystem II, devoid of outer and inner antennas. This is accompanied by a massive accumulation of protective carotenoids and proteins that scavenge harmful radicals. At the same time, several elements central to photoinhibition protection in C. reinhardtii, such as psbS, light harvesting complex stress‐related, photosystem II protein phosphorylation and state transitions are entirely absent or were barely detected. In addition, a carotenoid biosynthesis‐related protein accumulates in the thylakoid membranes of HL cells and may function in sensing HL and protecting the cell from photoinhibition. Taken together, a unique photoinhibition protection mechanism evolved in C. ohadii, enabling the species to thrive under extreme‐light intensities where other photosynthetic organisms fail to survive. Significance Statement: Analysis of the photosynthetic properties of a desert alga that thrives at extreme high light intensities revealed protection from photoinhibition driven by a unique protection mechanism that is significantly different from those described in other green alga and plants. [ABSTRACT FROM AUTHOR]

The separation of multiple products from microalgae using a biorefinery approach is essential for the economic sustainability of microalgae‐based products. In the current study, a technique for the simultaneous extraction of such products was investigated for the complete valorization of microalgae biomass. Three principal metabolites – chlorophylls, carbohydrates and proteins – were simultaneously fractionated from the biomass of isolated Chlorella thermophila using a modified version of the triphasic separation (TPS) process. Optimized process parameters were determined as: (i) ammonium sulfate as the salt; (ii) 40% (w/v) as the salt concentration; (iii) 1:1 as the salt/alcohol ratio; (iv) 0.25% (w/w) as biomass loading; (v) 6 min of homogenization time, and (vi) 10 000 rpm as homogenization speed. These optimized process parameters resulted in the simultaneous recovery of 71%, 40%, and 22% yields for proteins, carbohydrates, and chlorophylls, respectively. Ultrastructure analysis revealed that intracellular metabolites could be extracted without complete cell disruption. Finally, a comparative analysis between triphasic separation with and without homogenization demonstrated the economic feasibility of the optimized extraction process. [ABSTRACT FROM AUTHOR]

Microalgae are globally accepted source of fatty acids (FA) due to their cell's potential to efficiently accumulate triacylglycerides which contain a significant amount of fatty acids for biodiesel production. This study aimed to screen nine (09) green microalgae strains in the laboratory for their high biomass and lipid productivity. Various microalgae strains were cultured at 30°C, with a light to dark ratio of 16:8 h (10–12 klux of light intensity) and aeration supplementation of 2% CO2 for longer period of time. The fatty acids of all microalgae species which showed growth potential under photoautotrophic cultivation had similar fatty acids found in palm oil. The selected strains of Ankistrodesmus sp. IFRPD 1061 and Chlorella sp. IFRPD 1092 were used due to their high lipid productivity content, were cultivated in 100 L NS III medium in an open raceway pond, aerated with 2% v/v CO2. The biomass concentration and productivity, lipid concentration and productivity of Ankistrodesmus sp. IFRPD 1061 (0.865 g/L, 76.250 mg/L/d, 0.167 g/L, and 14.685 mg/L/d, respectively) were found to be higher than those of Chlorella sp. IFRPD 1092 (0.433 g/L, 31.250 mg/L/d, 0.137 g/L, and 8.528 mg/L/d, respectively). Ankistrodesmus sp. IFRPD 1061 showed potential results of growing microalgae under photoautotrophic cultivation for biodiesel production. [ABSTRACT FROM AUTHOR]

The thermodynamic instability of conventional aqueous foam‐stabilized surfactants is a critical bottleneck in the construction of porous materials. This illustration demonstrates porous materials were prepared conveniently via a high stable capillary foam using Chlorella and applied in the removal of Methylene Blue and Brilliant Green dyes with outstanding adsorption performance from water. More details can be found in article number e202400275 by Yongfeng Zhu, Aiqin Wang, and co‐workers...By Hui Yu; Yongfeng Zhu; Fangzhi Duan; Aiping Hui and Aiqin WangReported by Author; Author; Author; Author; Author [Extracted from the article]

Primary (eukaryote and procaryote) and secondary (eukaryote and eukaryote) endosymbioses are driving forces in eukaryotic cell evolution. These phenomena are still contributing to acquire new cell structures and functions. To understand mechanisms for establishment of each endosymbiosis, experiments that can induce endosymbiosis synchronously by mixing symbionts isolated from symbiont‐bearing host cells and symbiont‐free host cells are indispensable. Recent progress on endosymbiosis using Paramecium and their endonuclear symbiotic bacteria Holospora or symbiotic green alga Chlorella has been remarkable, providing excellent opportunities for elucidating host–symbiont interactions. These organisms are now becoming model organisms to know the mechanisms for establishing primary and secondary endosymbioses. Based on experiments of many researchers, we introduce how these endosymbionts escape from the host lysosomal fusion, how they migrate in the host cytoplasm to localize specific locations within the host, how their species specificity and strain specificity of the host cells are controlled, how their life cycles are controlled, how they escape from the host cell to infect more young host cell, how they affect the host viability and gene expression, what kind of substances are needed in these phenomena, and what changes had been induced in the symbiont and the host genomes. [ABSTRACT FROM AUTHOR]

Microalgae are diverse, with many gaps remaining in phylogenetic and physiological understanding. Thus, studying new microalgae species increases our broader comprehension of biological diversity, and evaluation of new candidates as algal production platforms can lead to improved productivity under a variety of cultivation conditions. Chlorella is a genus of fast‐growing species often isolated from freshwater habitats and cultivated as a source of nutritional supplements. However, the use of freshwater increases competition with other freshwater needs. We identified Chlorella desiccata to be worthy of further investigation as a potential algae production strain, due to its isolation from a marine environment and its promising growth and biochemical composition properties. Long‐read genomic sequencing was conducted for C. desiccata UTEX 2526, resulting in a high‐quality, near chromosome level, diploid genome with an assembly length of 21.55 Mbp in only 18 contigs. We also report complete circular mitochondrial and chloroplast genomes. Phylogenomic and phylogenetic analyses using nuclear, chloroplast, 18S rRNA, and actin sequences revealed that this species clades within strains currently identified as Nannochloris (Trebouxiophyceae, Chlorophyta), leading to its reclassification as Nannochloris sp. "desiccata" UTEX 2526. The mode of cell division for this species is autosporulation, differing from the type species N. bacillaris. As has occurred across multiple microalgae genera, there are repeated examples of Nannochloris species reclassification in the literature. This high‐quality genome assembly and phylogenetic analysis of the potential algal production strain Nannochloris sp. "desiccata" UTEX 2526 provides an important reference and useful tool for further studying this region of the phylogenetic tree. [ABSTRACT FROM AUTHOR]

The commercial production of carotenoids as bioactive commodities from microalgae has been severely limited due to the nature of the microalgal outer cell matrix. Microwave technology offers a rapid method for obtaining larger amounts of these biochemical compounds. The process facilitates cell‐wall rupture, releasing the inner cell components. Chlorella biomass, raised in an outdoor raceway pond, is used for downstream extraction of carotenoids by following the microwave‐assisted solvent extraction (MAE) approach. The response surface modeling (RSM) strategy was employed to optimize the two independent parameters, power and extraction time, with a two‐level central composite design (CCD). Acetone, hexane, methanol, hexane : acetone (1:1), hexane : ethanol (7:3) were used as solvents of choice. Acetone gave a total carotenoid yield of 0.061 ± 0.003 mg gm−1 under optimum microwave power and time; 130 W and 1.69 min. The optimized yield from hexane was 0.00173 ± 0.005 mg gm−1 with an exposure time of 1 min to 100 W. The total carotenoid yield of the methanol‐based extraction batch was 0.0371 ± 0.004 mg gm−1 with 157 W and 1 min of extraction time. The solvent mixtures of hexane : acetone gave 0.0398 ± 0.002 mg gm−1 (185 W for 1.7 min) and hexane : ethanol gave 0.0383 ± 0.004 mg gm−1 (195 W, 1.6 min), respectively. The results indicate a satisfactory outcome to the process. They also show microwave‐based extraction to be a fast, economic, reproducible, and repeatable method in comparison with the conventional strategies used for recovering the sensitive natural pigments. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

Carbon dioxide supplementation regulates the metabolism of photosynthetic organisms, initiating CO2 fixation through the central carbon metabolism and partitioning the carbon in various metabolic processes. It is important to understand the molecular mechanisms of carbon fixation and partitioning to control and regulate biomass and lipid production. In this context, we investigated the metabolic and physiological responses of a freshwater microalga, Chlorella saccharophila, supplemented with very low CO2 (VLC) (300 ppm or 0.03%) and high CO2 (HC) (30 000 ppm, or 3% v/v), for its potential as a biorefinery strain. Our results demonstrate that growth with HC was enhanced 1.4‐fold in comparison with VLC. We speculate that growth with VLC was supported by the central electron flow. Similar changes were observed in various biochemical constituents, i.e., lipids, proteins and carbohydrates. It was also observed that the total pigment productivity was 1.8‐fold higher with HC supplementation than in cultures supplemented with VLC, further indicating enhanced growth in HC. Applying qualitative metabolomics, we identified nearly 23 essential metabolites. There was an accumulation of sugars and antioxidants such as trehalose and α‐tocopherol in VLC as compared to HC. In conclusion, our objective is to understand HC supplementation in C. saccharophila UTEX247 and to provide valuable insights leading to enhanced biomass for the production of biofuels and high‐value biorenewables (B3) in the context of a circular bioeconomy by the valorization of carbon dioxide (CO2). © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

As third generation feedstock, microalgae are microorganisms that can grow only in the optimum conditions. There are parameters including the concentration of macro and microelements in nutrient solution, pH, temperature and light intensity that have significant impact on microalgal growth. In recent years, various sensing devices have been developed for sensitive measurement of these parameters during microalgal growth. In this study, a new potentiometric nitrate selective sensor was developed to indicate the nitrate uptake of microalgae and the effect of nitrate nutrient on microalgal growth, specifically, and this sensor was successfully applied to determine nitrate concentration in medium during microalgal growth. Moreover, the effects of nitrate, carbonate and phosphate concentration in the growth medium on biomass production of Chlorella minutissima were investigated by using Box–Behnken design method, and optimum conditions were determined for the highest biomass production of microalgae. As a result of the experiments, it was seen that the highest C. minutissima production was achieved using the medium consist of 2.63 g/L NaNO3, 0.35 g/L Na2CO3 and 0.4 g/L KH2PO4. Statistically, it was observed that there was a proportional relationship between the microalgae production and investigated parameters such as carbon, nitrogen and phosphate amounts of culture mediums. The electrode showed a wide linear range between 1.0 × 10−1 and 5.0 × 10−5 M with a detection limit of the 5 × 10−6 M and the response time was found as 10 s. The results showed that developed nitrate selective sensor could be successfully applied for continuous measurement of nitrate in microalgal productions at reduced cost. [ABSTRACT FROM AUTHOR]

Drying of Chlorella minutissima slurry was carried out in a single rotary drum dryer at varied drum surface temperature and rotational speed to achieve higher lipid yield for biodiesel conversion. Residual moisture content and lipid yield of the corresponding drum speed and drum surface temperature were mapped. Application of the machine learning tool classified the range of residual moisture content to be <10% (wet biomass) for high lipid recovery with an accuracy of 97%. Based on the drying time, lipid recovery, and energy consumption, drying at 80°C drum surface temperature with 0.3 rpm resulted ˃90% lipid recovery as compared to the bone‐dried biomass. The energy consumption of 7.328 kWh for 1 kg of dried biomass was recorded with profound reduction in drying time as compared to oven and tray drying of algal slurry. The fatty acid methyl ester profile of C. minutissima biodiesel constituted higher proportion of saturated fatty acids followed by monounsaturated fatty acid and polyunsaturated fatty acids. Various fuel characteristics, namely, viscosity, density, free glycerin, triglycerides, diglycerides, monoglycerides, copper strip corrosion, flash point, cetane index, iodine value, calorific value, acid value, saponification value, phosphorous, sulfur, water, and ash contents were analyzed, and showed values within the specified limits of national and international biodiesel standards. Thus, considering the drying time, energy consumption, and lipid recovery with suitable fuel properties, the drum dryer could be recommended for drying the microalgal slurry for large‐scale operation. [ABSTRACT FROM AUTHOR]

Lignocellulosic waste is the most abundant global renewable biomass source and contains significant amounts of pentoses. Thus, pentoses can be considered potential carbon sources for the culture media for microalgae cultivation. The present study aimed to determine whether the addition of D‐xylose and L‐arabinose and lighting variations influence the carbohydrate and protein profiles of Chlorella minutissima grown in tubular photobioreactors. The highest biomass concentration of 1.55 g L−1 was attained by the control cultures exposed to a light intensity of 40.50 μmol m−2 s−1. The highest carbohydrate accumulation (66.4%) was obtained through the combined use of 40.50 μmol m−2 s−1 light intensity, 19.16 mg L−1 D‐xylose, 0.89 mg L−1 L‐arabinose, and 0.125 g L−1 KNO3. A reduction in luminosity and the addition of pentoses altered the protein profile of Chlorella minutissima. Thus, growth and carbohydrate production can be stimulated by pentoses and adequate luminous intensity. Therefore, Chlorella minutissima can be considered a potential source of biomass for bioethanol production. [ABSTRACT FROM AUTHOR]

Algae–bacteria consortia have been proven effective in the removal of metal pollutants, but the effects of algal–bacterial ratio in the metal accumulation and resistance by this symbiotic system have not been systematically investigated. In this study, we set up consortia with various ratios of Chlorella salina–Bacillus subtilis, determined their growth, Cd accumulation, levels of intracellular glutathione (GSH), extracellular polysaccharide, phosphorus (P) in the culture medium, and functional groups of consortia after Cd treatments (0.1, 0.5, 1 mg L−1) for 7 days. With the addition of B. subtilis in the C. salina culture, the dry weight and specific growth rate of the consortia significantly increased compared with C. salina alone, reaching 68.33 mg and 0.382 (mg L−1) d−1 respectively at the 1:4 algal–bacterial ratio with 1 mg L−1 Cd treatment. Maximum Cd removal (51.66%) was also observed upon the same Cd exposure and algal–bacterial ratio. Cadmium was mostly taken up into cells at 1 mg L−1 Cd whereas its adsorption dominated the accumulation when Cd was 0.1 and 0.5 mg L−1. The amounts of extracellular polysaccharides, GSH, and P of the symbiotic system were also increased by the bacterial addition. Besides, Fouriertransform infrared (FTIR) spectroscopy analysis showed that functional groups like N–H, O–H, and P–O–C were involved in the Cd complexation. Taken together, a higher bacterial ratio promoted the Cd accumulation and detoxification by the C. salina–B. subtilis consortia through intra‐ and extracellular processes. [ABSTRACT FROM AUTHOR]

Chlorella‐associated bacteria can have a significant influence on facilitating higher Chlorella biomass yield due to their symbiotic relationship. In this study, non‐axenic Chlorella was cultivated in an airlift photobioreactor at high and low‐yield conditions. The associated bacterial diversity was analyzed using 16S rRNA metagenome sequencing. At high‐yield conditions, the bacterial load was observed in the range of 108‐1010CFU · mL−1, whereas at low‐yield conditions, bacteria were more dominant and observed in the range of 1014–1015 CFU · mL−1. The majority of the bacterial species associated with Chlorella at high‐yield conditions belongs to Proteobacteria and Bacteroidetes. Further, Bacteroidetes levels were decreased at low‐yield conditions and were highly diversified with Planctomycetes, Firmicutes, and 18 others. Predicted functional genes indicated that Chlorella‐associated bacteria have the enzymes involved in the metabolism and biosynthesis of B‐complex vitamins (i.e., vitamin B12, thiamin, biotin, pyridoxine, and riboflavin). A critical evaluation revealed that vitamin biosynthesis genes were more abundant at low‐yield conditions; however, vitamin B12 transport genes (B12 transport ATP‐binding protein, B12 substrate‐binding transportation, and B12 permease protein) were less abundant, indicating even though vitamins production occurs, but their availability to Chlorella was limited due to the lack of vitamin transport genes. Further, at high yield, Chlorella‐associated bacteria enabled higher growth by supplementing the vitamins. In contrast, at low‐yield condition—an increased bacterial load, diversity, and limited vitamin transport functional genes affected the Chlorella yield. It can be inferred that Chlorella yield was significantly affected by three factors: associated bacterial load, diversity, and transport functional genes of vitamins. [ABSTRACT FROM AUTHOR]

SUMMARY Paramecium bursaria has hundreds of chlorella in the cell. These symbiotic chlorella cells supply maltose, a photosynthetic product, to the host. Only symbiotic chlorella retains the ability to release maltose to the extracellular space, whereas free‐living chlorella does not. To provide the host with maltose, a maltose transporter localized on the symbiotic chlorella plasma membrane is required. However, the molecular identity of the maltose transporter and its properties are unknown. To better understand the characteristics of the maltose transporter, we investigated how maltose release by Chlorella variabilis is affected by the excess external maltose and several agents that inhibit ATP synthesis or disrupt the ion gradient across cell membranes. Our overall findings, including the observation that C. variabilis did not utilize maltose in the growth medium, led to the conclusion that the maltose transporter is likely a unidirectional and active transporter, which utilizes a proton gradient across the plasma membrane and does not use ATP as its energy source. [ABSTRACT FROM AUTHOR]

Heterotrophic cultivation of Chlorella has achieved commercial success, but the application of Chlorella biomass is still limited due to the high cost of biomass production. In this study, an effective and industrially scalable heterotrphic cultivation technology has been developed for a production strain Chlorella sorokiniana GT‐1. Under the optimized culturing conditions, the ultrahigh biomass concentration of 271 and 247 g L−1 was achieved in 7.5 L bench‐scale and 1000 L pilot‐scale fermenters, respectively. Technoeconomic (TE) analysis indicated that the production cost of C. sorokiniana GT‐1 could be reduced to $1601.27 per ton of biomass if the biomass concentration reached 200 g L−1, which is 24.2% lower than that of the reported highest Chlorella biomass production through fermentation with the same TE model. Under the same growth conditions, the maximum biomass concentration of a low‐starch mutant SLM2 was reduced to 93 g L−1, which was 54% lower than that of the wild type, indicating the capabilities of C. sorokiniana GT‐1 cells in accumulating large amounts of starch are essential for achieving the ultrahigh‐cell‐density under the heterotrophic conditions. In addition, the ultrahigh‐cell‐density growth potential of C. sorokiniana GT‐1 cells was inferred to be related to the intrinsic biological characteristics including the tolerance to low dissolved oxygen and a moderate doubling time under the heterotrophic conditions as well. The breakthrough in cultivation technology is promising for Chlorella industry and would expand its applications in food and feed. [ABSTRACT FROM AUTHOR]

Microalgae represent a potential solution to reduce CO2 emission exploiting their photosynthetic activity. Here, the physiologic and metabolic responses at the base of CO2 assimilation were investigated in conditions of high or low CO2 availability in two of the most promising algae species for industrial cultivation, Chlorella sorokiniana and Chlorella vulgaris. In both species, high CO2 availability increased biomass accumulation with specific increase of triacylglycerols in C. vulgaris and polar lipids and proteins in C. sorokiniana. Moreover, high CO2 availability caused only in C. vulgaris a reduced NAD(P)H/NADP+ ratio and reduced mitochondrial respiration, suggesting a CO2 dependent increase of reducing power consumption in the chloroplast, which in turn influences the redox state of the mitochondria. Several rearrangements of the photosynthetic machinery were observed in both species, differing from those described for the model organism Chlamydomonas reinhardtii, where adaptation to carbon availability is mainly controlled by the translational repressor NAB1. NAB1 homologous protein could be identified only in C. vulgaris but lacked the regulation mechanisms previously described in C. reinhardtii. Acclimation strategies to cope with a fluctuating inorganic carbon supply are thus diverse among green microalgae, and these results suggest new biotechnological strategies to boost CO2 fixation. High/low CO2 availability induces in Chlorella vulgaris and Chlorella sorokiniana specific cell responses as lipids remodelling, modulation of mitochondrial respiration and adaptations of the photosynthetic apparatus. [ABSTRACT FROM AUTHOR]

There have been limited studies on the effects of toxicity‐modifying factors, such as dissolved organic matter (DOM), on the toxicity of metal mixtures to aquatic biota. The present study investigated the effects of DOM concentration (low, 2.8 ± 0.1 mg C/L; high, 11 ± 1.0 mg C/L) and DOM source (predominantly terrestrial or microbial) on the chronic toxicity of copper (Cu) and nickel (Ni) binary mixtures to the green freshwater microalga Chlorella sp. This was assessed by using a full factorial design of 72‐h growth inhibition bioassays. Measured algal growth rate was compared with growth predicted by the concentration addition and independent action reference models. Model predictions were based on concentrations of dissolved metals, labile metals (measured by diffusive gradients in thin films [DGT]), and calculated free metal ions (determined by the Windermere Humic Aqueous Model). Copper/Ni mixture toxicity was synergistic to Chlorella sp. in the absence of added DOM, with evidence of metal concentration‐dependent toxicity at low effect concentrations. As DOM concentration increased, the mixture interaction changed from synergism to noninteraction or antagonism depending on the metal speciation method used. The DOM source had no significant effect on mixture interaction when based on dissolved and free metal ion concentrations but was significantly different when based on DGT‐labile metal concentrations. Ratio‐dependent mixture interaction was observed in all treatments, with increased deviation from the reference model predictions as the mixture changed from Ni‐ to Cu‐dominated. The present study demonstrated that both DOM concentration and source can significantly change metal mixture toxicity interactions and that these interactions can be interpreted differently depending on the metal speciation method used. Environ Toxicol Chem 2021;40:1908–1918. © 2021 SETAC [ABSTRACT FROM AUTHOR]

Bioactive compounds in algae have chain rings that protect the tissue from chemical damage and disease symptoms. In addition, algal bioactive agents have the ability to stimulate the immune system, protective and therapeutic effects against many diseases, including various types of cancers, coronary heart disease, premature aging, and arthritis. These bioactive compounds also have antioxidant, anticoagulant, antiviral, and anti‐inflammatory properties. It is very important to encapsulate these algal compounds for preserving bioactive properties. Two of the most efficient methods used for encapsulation are electrospraying and microemulsion techniques. Although electrospraying is a novel technique to produce nanoparticles in recent years, microemulsion is more conventional method compared with electrospraying. In this study, Chlorella protothecoides oil was encapsulated by using sodium alginate and chitosan biopolymers, and the effects of production parameters of electrospraying and microemulsion methods on the particle size and loading efficiency were investigated. Statistical modeling of critical parameters for particle sizing in microemulsion method and electrospraying technique, which is a novel approach to obtain microalgal oil‐loaded nanoparticles, was also presented. It was seen that electrospraying is suitable for obtaining smaller nanoparticles (123.9–610 nm), homogeneous distribution, and higher oil loading efficiency (60%–77%) compared with microemulsion method (756.9–1128.2 nm and 57%–73%). [ABSTRACT FROM AUTHOR]

SUMMARY: Although light is the driving force of photosynthesis, excessive light can be harmful. One of the main processes that limits photosynthesis is photoinhibition, the process of light‐induced photodamage. When the absorbed light exceeds the amount that is dissipated by photosynthetic electron flow and other processes, damaging radicals are formed that mostly inactivate photosystem II (PSII). Damaged PSII must be replaced by a newly repaired complex in order to preserve full photosynthetic activity. Chlorella ohadii is a green microalga, isolated from biological desert soil crusts, that thrives under extreme high light and is highly resistant to photoinhibition. Therefore, C. ohadii is an ideal model for studying the molecular mechanisms underlying protection against photoinhibition. Comparison of the thylakoids of C. ohadii cells that were grown under low light versus extreme high light intensities found that the alga employs all three known photoinhibition protection mechanisms: (i) massive reduction of the PSII antenna size; (ii) accumulation of protective carotenoids; and (iii) very rapid repair of photodamaged reaction center proteins. This work elucidated the molecular mechanisms of photoinhibition resistance in one of the most light‐tolerant photosynthetic organisms, and shows how photoinhibition protection mechanisms evolved to marginal conditions, enabling photosynthesis‐dependent life in severe habitats. [ABSTRACT FROM AUTHOR]

Photodecarboxylase from Chlorella variabillis (CvFAP) is one of the three known light-activated enzymes that catalyzes the decarboxylation of fatty acids into the corresponding C1- shortened alkanes. Although the substrate scope of CvFAP has been altered by protein engineering and decoy molecules, it is still limited to mono-fatty acids. Our studies demonstrate for the first time that long chain dicarboxylic acids can be converted by CvFAP. Notably, the conversion of dicarboxylic acids to alkanes still represents a chemically very challenging reaction. Herein, the light-driven enzymatic decarboxylation of dicarboxylic acids to the corresponding (C2-shortened) alkanes using CvFAP is described. A series of dicarboxylic acids is decarboxylated into alkanes in good yields by means of this approach, even for the preparative scales. Reaction pathway studies show that mono-fatty acids are formed as the intermediate products before the final release of C2-shortened alkanes. In addition, the thermostability, storage stability, and recyclability of CvFAP for decarboxylation of dicarboxylic acids are well evaluated. These results represent an advancement over the current state-of-the-art. [ABSTRACT FROM AUTHOR]

Novel composite films made of polyurethane (PU) and defatted Chlorella biomass (DCB) at different mass proportions (10–70 wt%) were prepared using polyethylene glycol (PEG) as a model polyol and hexamethylene diisocyanate (HMDI) as a coupling agent. Increasing DCB content led to a respective increase in tensile strength and elongation at break of the composites in the range of 33.9–116% and 69.6–248%, compared to the neat PU‐PEG film. As confirmed by Fourier transform infrared and scanning electron microscopy analysis, such improvement in mechanical properties can be attributed to the establishment of hydrogen bonds and other molecular interactions between isocyanate groups of PEG‐HMDI prepolymer and hydroxyl groups of DCB biofiller along with the uniform distribution of the incorporated DCB into the PU‐PEG based matrix. DCB incorporation at the highest content of 70% increased both antioxidant activity and bulk hydrophilicity of the composites by more than 69.3 and 85.0%, respectively, compared to the neat PU‐PEG. [ABSTRACT FROM AUTHOR]

Previously, we isolated Chlorella sp. HS2 (referred hereupon as HS2) from a local tidal rock pool and demonstrated its halotolerance and high biomass productivity under different salinity conditions. To further understand acclimation responses of this alga under high salinity stress, we performed transcriptome analysis of triplicated culture samples grown in freshwater and marine conditions at both exponential and stationary growth phases. The results indicated that the transcripts involved in photosynthesis, TCA, and Calvin cycles were downregulated, whereas the upregulation of DNA repair mechanisms and an ABCB subfamily of eukaryotic type ABC transporter was observed at high salinity condition. In addition, while key enzymes associated with glycolysis pathway and triacylglycerol (TAG) synthesis were determined to be upregulated from early growth phase, salinity stress seemed to reduce the carbohydrate content of harvested biomass from 45.6 dw% to 14.7 dw% and nearly triple the total lipid content from 26.0 dw% to 62.0 dw%. These results suggest that the reallocation of storage carbon toward lipids played a significant role in conferring the viability of this alga under high salinity stress by remediating high level of cellular stress partially resulted from ROS generated in oxygen‐evolving thylakoids as observed in a direct measure of photosystem activities. [ABSTRACT FROM AUTHOR]

Summary: High‐temperature bioconversion of lignocellulose into fermentable sugars has drawn attention for efficient production of renewable chemicals and biofuels, because competing microbial activities are inhibited at elevated temperatures and thermostable cell wall degrading enzymes are superior to mesophilic enzymes. Here, we report on the development of a platform to produce four different thermostable cell wall degrading enzymes in the chloroplast of Chlamydomonas reinhardtii. The enzyme blend was composed of the cellobiohydrolase CBM3GH5 from C. saccharolyticus, the β‐glucosidase celB from P. furiosus, the endoglucanase B and the endoxylanase XynA from T. neapolitana. In addition, transplastomic microalgae were engineered for the expression of phosphite dehydrogenase D from Pseudomonas stutzeri, allowing for growth in non‐axenic media by selective phosphite nutrition. The cellulolytic blend composed of the glycoside hydrolase (GH) domain GH12/GH5/GH1 allowed the conversion of alkaline‐treated lignocellulose into glucose with efficiencies ranging from 14% to 17% upon 48h of reaction and an enzyme loading of 0.05% (w/w). Hydrolysates from treated cellulosic materials with extracts of transgenic microalgae boosted both the biogas production by methanogenic bacteria and the mixotrophic growth of the oleaginous microalga Chlorella vulgaris. Notably, microalgal treatment suppressed the detrimental effect of inhibitory by‐products released from the alkaline treatment of biomass, thus allowing for efficient assimilation of lignocellulose‐derived sugars by C. vulgaris under mixotrophic growth. [ABSTRACT FROM AUTHOR]

To test the hypothesis that rotifers release one or more chemical microalgal growth inhibitors in addition to devouring the microalgal cells, the effects of different concentrations of filtered, bacteria‐free, rotifer culture filtrate (RCF) on the growth and physiological parameters of Chlorella sp., and the response of Chlorella sp. at different starting cell densities to 10% RCF, were studied. The results show that RCF significantly decreased Chlorella cell densities during the incubation, suggesting that rotifers release some chemical(s) that inhibit microalgal cell growth. Chlorella cell densities decreased with increasing RCF concentration. Increasing the initial cell density of Chlorella dispersed the inhibitory chemical(s) present in 10% RCF over more cells, reducing their effect. The results confirm that the action of the chemical(s) released by rotifers on microalgal cell growth was dependent on both the RCF concentration and the exposure time. They also demonstrate that ≥10% RCF significantly inhibited photosynthesis and respiration, which would account for some of the decreased Chlorella cell growth in the presence of RCF. Calculations based on the data indicate that the rotifer‐derived chemical(s) released hourly from each rotifer inhibits growth by 45.5 microalgal cells in addition to the rotifer predation, with a 48 h LC50 value of 18.8% RCF. Based on these results, fresh medium instead of the old culture medium was contaminated by the rotifers. [ABSTRACT FROM AUTHOR]

Microalgae are potential candidate for biofuel production as alternative one for fossil fuels. CO2 in flue gas is available carbon source to support microalgae growth. In this study, the effects of different concentrations of the simulated flue gas onto algal growth and photosynthetic activity were evaluated for both Chlorella sp. AE10 and Chlorella sp. Cv. The growth profiles were correlated by a simple kinetic model. It was indicated that the simulated flue gas led to low pH and the photosynthetic activity was partially destroyed. Chlorella sp. Cv can tolerate full simulated flue gas, 10% CO2 + 200 ppm NOx + 100 ppm SOx. The pH in medium maintained at 6 and the photosynthetic activity was more than 0.6 at the first 6 days. If the concentration of NOx was more 100 ppm and that of SOx was more than 50 ppm, the pH was declined to 4 at day 2 or 3 for Chlorella sp. AE10. At the same time, the related photosynthetic activities of Chlorella sp. AE10 were less than 0.4, which was not suitable for algal growth. It was shown that Chlorella sp. Cv could be used for CO2 fixation from the simulated flue gas. [ABSTRACT FROM AUTHOR]

BACKGROUND Chlorella protothecoides is one of the most widely commercialized and studied microalgae species. Recent research reported improved emulsifying properties of the insoluble protein fraction from C. protothecoides after thermal–acid treatment. RESULTS: In this research, we studied the influence of ionic strength (sodium chloride 50–500 mmol L−1 or calcium chloride 5–50 m mol L−1) and pH (2–9) on the stability of oil‐in‐water emulsions prepared by 3% (w/w) of the untreated insoluble microalgae protein fraction or hydrolysates obtained after treatment with hydrochloric acid at 65 °C (Hydrolysates 65) or 85 °C (Hydrolysates 85) for 4 h. The emulsions were prepared by mixing 10% (w/w) oil and homogenized at 68.9 MPa. The ionic strength and pH were, subsequently, adjusted. The mean particle diameter of emulsions remained constant despite extensive variations in ionic strength or pH. Emulsion droplets stabilized by Hydrolysates 85 were stable against coalescence at all ionic strengths or pH values tested. CONCLUSION: The results indicate a high potential to use acid‐hydrolyzed insoluble microalgae protein fractions for the formulation of various emulsion‐based food systems. © 2020 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Summary: Chlorella microalgae are increasingly used for various purposes such as fatty acid production, wastewater processing, or as health‐promoting food supplements. A mass spectrometry‐based survey of N‐glycan structures of strain collection specimens and 80 commercial Chlorella products revealed a hitherto unseen intragenus diversity of N‐glycan structures. Differing numbers of methyl groups, pentoses, deoxyhexoses, and N‐acetylglucosamine culminated in c. 100 different glycan masses. Thirteen clearly discernible glycan‐type groups were identified. Unexpected features included the occurrence of arabinose, of different and rare types of monosaccharide methylation (e.g. 4‐O‐methyl‐N‐acetylglucosamine), and substitution of the second N‐acetylglucosamine. Analysis of barcode ITS1–5.8S–ITS2 rDNA sequences established a phylogenetic tree that essentially went hand in hand with the grouping obtained by glycan patterns. This brief prelude to microalgal N‐glycans revealed a fabulous wealth of undescribed structural features that finely differentiated Chlorella‐like microalgae, which are notoriously poor in morphological attributes. In light of the almost identical N‐glycan structural features that exist within vertebrates or land plants, the herein discovered diversity is astonishing and argues for a selection pressure only explicable by a fundamental functional role of these glycans. [ABSTRACT FROM AUTHOR]

Several strains of terrestrial algae isolated from biological soil crusts in Germany and Ukraine were identified by morphological methods as the widely distributed species Dictyosphaerium minutum (=Dictyosphaerium chlorelloides). Investigation of the phylogeny showed their position unexpectedly outside of Chlorellaceae (Trebouxiophyceae) and distantly from Chlorella chlorelloides, to which this taxon was attributed after revision of the genus Chlorella based on an integrative approach. SSU rRNA phylogeny determined the position of our strains inside a clade recently described as a new genus of the cryptic alga Xerochlorella olmiae isolated from desert biological soil crusts in the United States. Investigation of the morphology of the authentic strain of X. olmiae showed Dictyosphaerium‐like morphology, as well as some other characters, common for our strains and morphospecies D. minutum. The latter alga was described as terrestrial and subsequently united with the earlier described aquatic representative D. chlorelloides because of their similar morphology. The revision of Chlorella mentioned above provided only one aquatic strain (D. chlorelloides), which determined its position in the genus. But terrestrial strains of the morphospecies were not investigated phylogenetically. Our study showed that the terrestrial D. minutum is not related to the morphologically similar D. chlorelloides (=Chlorella chlorelloides, Chlorellaceae), and instead represented a separate lineage in the Trebouxiophyceae, recently described as genus Xerochlorella. Therefore, revision of Xerochlorella is proposed, including nomenclatural combinations, epitypifications, and emendations of two species: X. minuta and X. dichotoma. New characters of the genus based on investigation of morphology and ultrastructure were determined. [ABSTRACT FROM AUTHOR]

Several strains of terrestrial algae isolated from biological soil crusts in Germany and Ukraine were identified by morphological methods as the widely distributed species Dictyosphaerium minutum (=Dictyosphaerium chlorelloides). Investigation of the phylogeny showed their position unexpectedly outside of Chlorellaceae (Trebouxiophyceae) and distantly from Chlorella chlorelloides, to which this taxon was attributed after revision of the genus Chlorella based on an integrative approach. SSU rRNA phylogeny determined the position of our strains inside a clade recently described as a new genus of the cryptic alga Xerochlorella olmiae isolated from desert biological soil crusts in the United States. Investigation of the morphology of the authentic strain of X. olmiae showed Dictyosphaerium‐like morphology, as well as some other characters, common for our strains and morphospecies D. minutum. The latter alga was described as terrestrial and subsequently united with the earlier described aquatic representative D. chlorelloides because of their similar morphology. The revision of Chlorella mentioned above provided only one aquatic strain (D. chlorelloides), which determined its position in the genus. But terrestrial strains of the morphospecies were not investigated phylogenetically. Our study showed that the terrestrial D. minutum is not related to the morphologically similar D. chlorelloides (=Chlorella chlorelloides, Chlorellaceae), and instead represented a separate lineage in the Trebouxiophyceae, recently described as genus Xerochlorella. Therefore, revision of Xerochlorella is proposed, including nomenclatural combinations, epitypifications, and emendations of two species: X. minuta and X. dichotoma. New characters of the genus based on investigation of morphology and ultrastructure were determined. [ABSTRACT FROM AUTHOR]

Summary: Biological control agents including microbes and their products have been studied as sustainable crop protection strategies. Although aquatic microalgae have been recently introduced as a biological control agent, the underlying molecular mechanisms are largely unknown. The aim of the present study was to investigate the molecular mechanisms underlying biological control by microalga Chlorella fusca. Foliar application of C. fusca elicits induced resistance in Arabidopsis thaliana against Pseudomonas syringae pv. tomato DC3000 that activates plant immunity rather than direct antagonism. To understand the basis of C. fusca‐triggered induced resistance at the transcriptional level, we conducted RNA sequencing (RNA‐seq) analysis. RNA‐seq data showed that, upon pathogen inoculation, C. fusca treatment primed the expression of cysteine‐rich receptor‐like kinases, WRKY transcription factor genes, and salicylic acid and jasmonic acid signalling‐related genes. Intriguingly, the application of C. fusca primed pathogen‐associated molecular pattern ‐triggered immunity, characterized by reactive oxygen species burst and callose deposition, upon flagellin 22 treatment. The attempts to find C. fusca determinants allowed us to identify d‐lactic acid secreted in the supernatant of C. fusca as a defence priming agent. This is the first report of the mechanism of innate immune activation by aquatic microalga Chlorella in higher plants. Significance Statement: Aquatic microalgae have been recently used as bioprotectants and biostimulants in crop plants; however, the underlying molecular mechanism remains unclear. Here, we demonstrate for the first time that the priming of PAMP‐triggered immunity induced by the aquatic microalgae Chlorella fusca against Pseudomonas syringae pv. tomato DC3000 in land plant Arabidopsis. [ABSTRACT FROM AUTHOR]

BACKGROUND Gut microbiota are major contributors to host metabolism and are considered as potential targets of novel therapeutics. Microalgae have a strong potential for use as prebiotics because they are a rich source of proteins, fatty acids, fiber, and minerals for nutritional supplementation in humans. Nevertheless, there has been insufficient research into the effect of microalgae on gut microbiota. To investigate the effects of three edible microalgae (Chlorella vulgaris, Chlorella protothecoides, and Schizochytrium sp.) on gut microbiota, simulated digestion and colonic fermentation were examined. RESULTS: Following in vitro digestion, the microalgae displayed different levels of bioaccessibility and the nutrient analysis revealed that unabsorbed nutrients during the digestion process could be used for colonic fermentation. Following colonic fermentation, the control, inulin, and microalgae groups displayed different metabolite tendencies when investigated with nuclear magnetic resonance (NMR) spectroscopic analysis. In particular, microalgae supplementation increased the proportion of propionate in the colonic culture (control: 19.14%, Inulin: 18.38%, C. vulgaris: 25.80%, C. protothecoides: 25.46%, and Schizochytrium sp.: 25.56%). Microbial profiling analysis using 16S rRNA gene sequencing also disclosed that the relative abundance of Bacteroides (control: 1.91%, inulin: 2.61%, C. vulgaris: 14.77%, C. protothecoides: 11.17%, and Schizochytrium sp.: 5.51%) and Dialister (control: 0.08%, inulin: 2.06%, C. vulgaris: 6.79%, C. protothecoides: 4.45%, and Schizochytrium sp.: 4.48%), involved in propionate metabolism increased more than in the inulin group. CONCLUSION: Our findings suggest the potential use of microalgae as a functional food to increase propionate generation because propionate has been reported to be effective in weight loss and the inhibition of pathogen infection. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The environmental risk assessment of rare earth elements (REEs) requires data on their potential toxicity. In the present study, the toxicity of lanthanum (La) and cerium (Ce) was studied in relation to metal speciation in solution. For both La and Ce, the use of organic ligands demonstrated that the calculated free ion concentration was a good indicator of toxicity. Whether in the absence or presence of organic ligands, when based on free ion concentrations, the obtained half‐maximal effective concentrations were similar. When all generated data were pooled, Ce and La showed identical toxicity thresholds after 120 h of exposure with free ion concentration–based median effective concentration values (95% confidence intervals) of 0.48 (0.38–0.60) µM and 0.47 (0.36–0.61) µM for La3+ and Ce3+, respectively. The inhibition of algal growth was also correlated with the intracellular lanthanide concentrations, regardless of the ligand used. Finally, increasing the ambient calcium concentration protected the test algae by reducing the amount of lanthanide internalized into the cells. These results suggest that, at constant pH (5.5), REE accumulation and toxicity are linked to the free ion concentration and ambient calcium concentration, as predicted by the biotic ligand model. Environ Toxicol Chem 2020;39:996–1005. © 2020 SETAC [ABSTRACT FROM AUTHOR]

BACKGROUND: Recently, wastewater effluents from animal farms have been treated using microalgae for the removal of organic and inorganic compounds. Swine wastewater (SW) and wastewater treated by anaerobic digestion (TW) were used as culture media for a wild strain of microalga, Chlorella sp. (Chlorophyta), previously isolated for our research group. This was cultivated under laboratory conditions in a batch culture, and then inoculated in a cascade thin‐layer reactor under outdoor conditions. The kinetic behavior, nutrient removal (COD, NH4+‐N, NO3−‐N and PO34−‐P) efficiency and biochemical composition of the microalga biomass were evaluated. RESULTS: SW supported the highest growth (339 × 106 cells mL−1 and μ = 0.42 d−1) and the maximal removal of COD (91%), nitrates (87%), ammonium (45%) and phosphate (70%) in a batch culture. Whereas, in continuous cultivation, an adequate operation was achieved at temperatures up to 42 °C, with removals greater than 80% of COD, 70% of nitrates, 90% of ammonium and 60% of phosphates. Also, the produced biomass achieved the highest content of proteins (386 mg g−1 dry weight), carbohydrates (291.49 mg g−1 dry weight) and saturated and monounsaturated fatty acids, reaching 74.76% of total fatty acids. CONCLUSIONS: The SW medium showed greater growth of Chlorella than TW using the outdoor thin‐layer cascade reactor. This is an opportunity to use wastewater as nutrient to obtain biomass enriched in compounds with various possibilities for application. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Grazing behaviour between protozoa and phytoplankton exists widely in planktonic ecosystems. Poterioochromonas malhamensis is a well‐known and widespread mixotrophic flagellate, which is recognized to play an important role within marine and freshwater planktonic ecosystems and regarded as the greatest contamination threat for mass algal cultures of Chlorella. In this study, a comprehensive range of factors, including morphological characters, biochemical compositions, and specific growth rate of ten species or strains of Chlorella, were evaluated for their effect on the feeding ability of P. malhamensis, which was assessed by two parameters: the clearance rate of P. malhamensis on Chlorella spp. and the specific growth rate of P. malhamensis. The results showed that the clearance rate of P. malhamensis was negatively correlated with cell wall thickness and specific growth rate of Chlorella spp., while the specific growth rate of P. malhamensis was positively correlated with carbohydrate percentage and C/N ratio and negatively correlated with protein, lipid percentage, and nitrogen mass. In conclusion, the factors influencing feeding selectivity include not only the morphological character and chemical composition of Chlorella, but also its population dynamics. Our study provides useful insights into the key factors that affect the feeding selectivity of P. malhamensis and provides basic and constructive data to help in screening for grazing‐resistant microalgae. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the influence of different carbon dioxide (CO2) concentrations on the distribution of carbon forms in the culture medium and the biomass production and biomolecules productivity of the strain Chlorella fusca LEB 111. In this study, experiments were carried out in which C. fusca cultures were exposed to different CO2 concentrations, 0.03% (0.08 mlCO2 mlmedium−1 days−1), 5% (0.18 mlCO2 mlmedium−1 days−1), and 15% vol/vol CO2 (0.54 mlCO2 mlmedium−1 days−1). Among the carbon chemical species distributions in the culture medium, bicarbonate was predominant (94.2–98.9%), with the highest quantitative percentage in the experiment receiving a 15% CO2 injection. C. fusca LEB 111 cultivated with 15% CO2 showed the highest biomass productivity (194.3 mg L−1 days−1) and CO2 fixation rate (390.9 mg L−1 days−1). The carbohydrate productivity in the culture that received 15% CO2 was 46.2% higher than the value verified for the culture with the addition of CO2 from the air (0.03% CO2). In addition, CO2 concentration providing increases of 0.03–15% to C. fusca cultures resulted in a 31.6% increase in the lipid productivity. These results showed that C. fusca can be used for CO2 bioconversion and for producing biomass with potential applications for biofuels and bioproducts. [ABSTRACT FROM AUTHOR]

Inspired by the antifouling strategies of fluorescent corals and Gulf parrotfish, a novel polydimethylsiloxane (PDMS)–phosphor–silicone rubber sandwich‐structure coating is fabricated for combating biofouling. The coatings can emit weak light during night hours and have hydrophilic surfaces. The effectiveness of the coatings against various algae and bacteria, namely, Chlorella, Nitzschia closterium f. minutissima, gram‐negative Paracoccus pantotrophus, and gram‐positive Bacillus subtili is investigated. The results show that the PDMS–phosphor–silicone rubber sandwich‐structure coatings have broad‐spectrum antifouling performances. The results also demonstrate that surface hydrophilicity can effectively reduce adhesion of algae and bacteria, and that fluorescence inhibits only algae. In addition, the effect is revealed of the wavelength of different colored phosphor layers on antifouling capability to resist Chlorella and N. closterium f. minutissima. Blue (427 nm), yellow (663 nm), and red (731 nm) phosphor layers are conducive to combating Chlorella and N. closterium f. minutissima, whereas the green (512 nm) phosphor layer shows no distinct effect on resisting Chlorella and N. closterium f. minutissima. These findings can contribute to the development of new antifouling coatings. In addition, the antifouling capabilities of these coatings have potential for further improvement and development. The sandwich‐structure materials fabricated in this study should prove very useful in practical applications. [ABSTRACT FROM AUTHOR]