Microalga Scenedesmus Obliquus Research Articles

Enhanced Scenedesmus obliquus Cultivation in Plastic-Type Flat Panel Photobioreactor for Biodiesel Production

A plastic-type flat panel photobioreactor (PTFPP) prototype was designed for microalgae cultivation as biodiesel feedstock. The growth, biomass, and lipid production of the oleaginous microalga Scenedesmus obliquus were optimized through the enhanced design and cultivation conditions in the PTFPP. The optimization conditions include cultivation of the microalga in a flat panel photobioreactor manufactured from a 10 µm-thick plastic sheet with dimensions of 40 cm in width and 60 cm in height. The width of the designed plastic bags was adjusted by “4 ports” of circular adhesion points which make the volumetric cultural capacity 5 L. Cultivation of the microalga was optimized through the replacement of the sodium nitrate of the BBM medium with urea as a nitrogen source. Cultivation bags were subjected to continuous illumination with 3000 lux white, fluorescent lamps and aerated with 1.5 L air/min (equal to 0.3 VVM). Biomass production from the designed PTFPP reached 3 g/L with around 40% lipid content (on a dry weight basis). Based on a GC-MS analysis of the produced fatty acid methyl ester (biodiesel) from S. obliquus, the percentage of C16 and C18 fatty acids reached more than 90% of the defined fatty acids. Out of this percentage, 66.6% were unsaturated fatty acids. The produced fatty acid profile of the S. obliquus biomass cultivated in the designed PTFPP prototype could be considered a suitable feedstock for biodiesel production.

Light-induced aquaculture wastewater valorization, nutrient recovery, and microalgae biomass production in a biocathode-assisted microbial fuel cell

The present study investigates how well the light quality (white, blue, and red light) affects the growth and biochemical profiling of freshwater microalga Scenedesmus obliquus grown on aquaculture wastewater as a nutrient source in a biocathode microbial fuel cell (MFC). The findings show that the electrochemical behaviour of the MFCs varied with the use of different wavelengths, suggesting that light quality and photosynthetic evolved oxygen increased MFC voltage. Sc. obliquus showed the highest percentage of nutrient removal for blue light-operated biocathode MFC. Blue light maximized biomass production with a cell density of 1.54 ± 0.065 OD680 and Chl-a concentration of 12 ± 1.2 mgL−1 during 6-day cultivation. Valorization of aquaculture using MFC proved successful in nutrient recovery and microalgae biomass production, primarily upon exposure to blue light.

Processing and characterization of antimicrobial bioplastic films based on green microalgae Scenedesmus obliquus extract-loaded polyurethane

The green microalga Scenedesmus obliquus, isolated from the Egyptian environment, was used for the synthesis of bio-based plastic materials. Polyurethane (PU) was blended with different proportions (0%, 10%, 20%, and 40%) of chloroform extract to form bioplastic films. The bioplastic films were characterized using water vapor transmission rate measurements and scanning electron microscopy (SEM). The WVTR of pure PU was 193.37 g/m2. day, while the values of algae/PU films were 129.74, 122.56, and 99.75 g/m2.day. S. obliquus reported having Palmitic, which possesses antimicrobial activity and acts as an effective antimicrobial agent in the synthesized bioplastic films. Antimicrobial activity of the algal extract and the synthesized bioplastic films were tested against two Gram-positive bacteria; Staphylococcus aureus, Enterococcus faecalis, two Gram-negative bacteria; Escherichia coli, Pseudomonas aeruginosa, and Candida albicans as a model for fungi. The results indicated that S. obliquus extract exhibited a clear antimicrobial activity against all tested microbes. The antimicrobial rate of bioplastic films containing 40% of the extract reached 100% after 2 h of contact with E. coli and E. faecalis. In conclusion, this study offers a promising future for the use of biodegradable antimicrobial bioplastic films as an affordable and environmentally friendly alternative to plastics in many applications.

Impacts of organic solvent toxicity on resource recovery from Scenedesmus obliquus biomass after lipid extraction

Residual biomass obtained after microalgae lipid extraction is rich in carbon and nutrients and has great potential for use as a substrate in anaerobic digestion, microalgae cultivation, and plant cultivation. However, residues from organic solvents can make it unfeasible to use the biomass in these applications. In this work, ethyl acetate (EA) and hexane-ethanol mixture (HE) were used to evaluate the yield and quality of lipids extracted from the microalga Scenedesmus obliquus BR003. Also, the toxicity of these solvents to anaerobic digestion, microalgae cultivation, and seed germination was evaluated at concentrations similar to those found in the residual biomass after lipid extraction. Lipid yields were 83.1% and 55.4% for HE and EA, respectively, where EA extracted mostly neutral lipids. In the HE mixture, hexane showed no significant effect in toxicity assays due to its low solubility in the aqueous fraction. However, ethanol in this mixture migrates to the aqueous phase, and the effective concentrations at 50% (EC50) were 3.78, 26.97, and 4.97 g L−1 for methanogenic archaea, S. obliquus, and lettuce seeds, respectively. The EA showed EC50 values of 18.74, 18.02, and 5.85 g L−1 for methanogenic archaea, S. obliquus, and lettuce seeds, respectively. The EA was less toxic to anaerobic microorganisms and lettuce seeds when compared to ethanol, which was less toxic to S. obliquus, making EA an environmentally friendly solvent for industrial use. Our study provides novel information on the criteria of solvent selection when aiming at resource recovery from residual microalgae biomass after lipid extraction.

Metabonomics analysis of microalga Scenedesmus obliquus under ciprofloxacin stress

The wide use of antibiotics in aquaculture has triggered global ecological security issue. Microalgal bioremediation is a promising strategy for antibiotics elimination due to carbon recovery, detoxification and various ecological advantages. However, a lack of understanding with respect to the corresponding regulation mechanism towards antibiotic stress may limit its practical applicability. The microalga Scenedesmus obliquus was shown to be capable of effectively eliminating ciprofloxacin (CIP), which is a common antibiotic used in aquaculture. However, the corresponding transcriptional alterations require further investigation and verification at the metabolomic level. Thus, this study uncovered the metabolomic profiles and detailed toxic and defense mechanisms towards CIP in S. obliquus using untargeted metabolomics. The enhanced oligosaccharide/polyol/lipid transport, up-regulation of carbohydrate and arachidonic acid metabolic pathways and increased energy production via EMP metabolism were observed as defense mechanisms of microalgal cells to xenobiotic CIP. The toxic metabolic responses included: (1) down-regulation of parts of mineral and organic transporters; (2) electrons competition between antibiotic and NAD during intracellular CIP degradation; and (3) suppressed expression of the hem gene in chlorophyll biosynthesis. This study describes the metabolic profile of microalgae during CIP elimination and reveals the key pathways from the perspective of metabolism, thereby providing information on the precise regulation of antibiotic bioremediation via microalgae.

Comparative toxicity assessment of individual, binary and ternary mixtures of SiO2, Fe3O4, and ZnO nanoparticles in freshwater microalgae, Scenedesmus obliquus: Exploring the role of dissolved ions

Metal oxide nanoparticles (NPs) are considered among the most prevalent engineered nanomaterials. To have a deeper understanding of the mode of action of multiple metal oxide nanoparticles in mixtures, we have used a unicellular freshwater microalga Scenedesmus obliquus as a model organism. The toxicity of silicon dioxide (SiO2), iron oxide (Fe3O4), and zinc oxide (ZnO) NPs was studied individually as well as in their binary (SiO2 + Fe3O4, Fe3O4 + ZnO, and ZnO + SiO2) and ternary (SiO2 + Fe3O4 + ZnO) combinations. The effects of metal ions from ZnO and Fe3O4 were investigated as well. The results observed from the study, showed that a significant amount of toxicity was contributed by the dissolved ions in the mixtures of the nanoparticles. Decreases in the cell viability, ROS generation, lipid peroxidation, antioxidant enzyme activity, and photosynthetic efficiency were analyzed. Among all the individual particles, ZnO NPs showed the maximum effects and increased the toxicities of the binary mixtures. The binary and ternary mixtures of the NPs clearly showed increased toxic effects in comparison with the individual entities. However, the ternary combination had lesser toxic effects than the binary combination of Fe3O4 + ZnO. The decline in cell viability and photosynthetic efficiency were strongly correlated with various oxidative stress biomarkers emphasizing the crucial role of reactive oxygen species in inducing the toxic effects. The findings from this study highlight the importance of evaluating the combinatorial effects of various metal oxide NPs as part of a comprehensive ecotoxicity assessment in freshwater microalgae.

Effects of Polystyrene Microparticles on Growth and Physiological Metabolism of Microalgae Scendesmus obliquus

Plastic products are widely used due to their lightness, durability, low cost, and malleability, and their threat to the environment is becoming increasingly apparent. However, the detailed mechanism of such an effect is unclear. Due to improper treatment, microplastic contamination is very much studied in the areas around sewage outfalls or some plastic manufacturers, and its content is high. To investigate the ecological impact of microplastics in this particular area, we evaluated the toxic effect of polystyrene microplastics (PS-MPs) on the microalgae Scenedesmus obliquus (S. obliquus). In particular, the cell growth, photosynthesis, antioxidant enzyme activity, membrane permeability, and morphology of the microalgae in the presence of different PS-MP concentrations were monitored. These new data revealed an increase in microalgae cell growth as an early response to low-dose PS-MP exposure with a maximum inhabitation rate of −3.33%. In contrast, a higher concentration of PS-MP solution leads to a significant inhibition within the test concentration, with a maximum inhabitation rate of 43.62%. Meanwhile, a decreased photosynthesis activity of S. obliquus was observed during the exposure. Moreover, PS-MPs induced oxidative damage to the algae cells, exhibiting decreased antioxidant activities and enhanced lipid peroxidation reactions, as evidenced by the reduction in the superoxide dismutase (SOD) level and increased malondialdehyde (MDA) content, as well as damaged cell membrane and soluble protein. Collectively, our study systematically investigates the toxicity of microplastics on microalgae, providing a deep insight into the possible influences of plastic pollution on the whole food web in the aquatic ecosystem.

Using the solution of self-settling microalgae Scenedesmus obliquus as processing medium for hydrothermal liquefaction of biomass

Microalgae has gathered significant interest as a promising feedstock for biocrude production through hydrothermal liquefaction (HTL). However, the challenge of microalgae harvesting presents a significant obstacle to its economic viability and technical feasibility. This study aimed to overcome the complexities of microalgae harvesting processes by exploiting the self-settling characteristic of microalgae Scenedesmus obliquus (S. obliquus). The supernatant was discarded, and the S. obliquus solution was utilized as the processing medium for HTL of various types of biomass. HTL of Chlorella pyrenoidosa (C. pyrenoidosa) in S. obliquus solution at 300 °C resulted in a synergistic increase in biocrude yield (approximately 10 wt%, daf); however, increasing the temperature to 350 °C diminished the observed synergy. HTL of spent coffee grounds in S. obliquus solution generated 39.0 wt% (daf) and 45 wt% (daf) biocrude at 300 °C and 350 °C, respectively, with no synergistic effect observed. Conversely, macroalgae Enteromorpha prolifera (E. prolifera) and sawdust, which had a high carbohydrate content, showed antagonistic effects on biocrude yield when S. obliquus solution was used at high temperatures (350 °C). These observations were further verified by carrying out HTL of carbohydrate model component in S. obliquus solution. Principal component analysis of product yields was performed in this study, and it revealed that HTL of C. pyrenoidosa, protein, and lipid were significantly different from spent coffee grounds, E. prolifera, sawdust, and carbohydrate. Overall, depending on the feedstock used, the self-settling S. obliquus solution could serve as a promising HTL processing medium for biocrude production, eliminating the need for microalgae dewatering processes and the consumption of additional freshwater as an HTL processing medium.

Unmasking effects of masks: Microplastics released from disposable surgical face masks induce toxic effects in microalgae Scenedesmus obliquus and Chlorella sp.

During the COVID-19 pandemic billions of face masks were used since they became a necessity in everyone's lives. But these were not disposed properly and serve as one of the most significant sources of micro and nano plastics in the environment. The effects of mask leached plastics in aquatic biota remains largely unexplored. In this work, we quantified and characterized the released microplastics from the three layers of the mask. The outer layer of the face mask released more microplastics i.e., polypropylene than middle and inner layers. We investigated and compared the acute toxic effects of the released microplastics between Scenedesmus obliquus and Chlorella sp. The results showed a decrease in cell viability, photosynthetic yield, and electron transport rate in both the algal species. This was accompanied by an increase in oxidative stress markers such reactive oxygen species (ROS) and malondialdehyde (MDA) content. There was also a significant rise of antioxidant enzymes such as superoxide dismutase (SOD) and catalase (CAT) in both the algal cells. Furthermore, morphological changes like cell aggregation and surface chemical changes in the algae were ascertained by optical microscopy and FTIR spectroscopy techniques, respectively. The tests confirmed that Scenedesmus obliquus was more sensitive than Chlorella sp. to the mask leachates. Our study clearly revealed serious environmental risk posed by the released microplastics from surgical face masks. Further work with other freshwater species is required to assess the environmental impacts of the mask leachates.

Integrating biological and chemical CO2 sequestration using green microalgae for bioproducts generation

Microalgae cultivation is considered an attractive negative emission technology (NET) due to its ability to remove carbon dioxide (CO2) from the atmosphere as well as from flue gases. Moreover, some microalgae can uptake dissolved carbon in the form of bicarbonate (HCO3-) and grow well by removing nutrients from various wastewater effluents without competing with freshwater resources. Conventional carbon mineralization is another NET where carbon is fixed into carbonate minerals such as calcite (CaCO3), magnesite (MgCO3), nesquehonite (MgCO3-3H2O), and nahcolite (NaHCO3), which can be reused in various applications such as construction and cosmetics, and in this case, to supply carbon to microalgae. Previous initial laboratory studies demonstrated the possibility of using metastable carbonates as a source of carbon for biomass growth of the freshwater microalga Scenedesmus obliquus. In this study, we present results from an experimental and modeling work where 100 L open raceway reactors were used to grow an algae polyculture using industrial nitrogen-rich wastewater. In addition, carbonates such as MgCO3-3H2O and sodium carbonate (Na2CO3) were added to the ponds to primarily buffer the pH and maintain it within the acceptable algae physiological values and to provide extra carbon to the cultures. Cultures using BG-11 growth medium and without addition of carbonates were run as controls. Continuous online monitoring of pH, temperature, and dissolved oxygen was performed while nutrients content and dry weight of algae culture were measured offline daily. A mathematical model coupled with geochemistry was implemented to describe the overall process of algae growth, carbonate dissolution, and solution composition. Biomass harvested from the raceway reactors was concentrated and oil and fatty acid methyl esters (FAME) content were determined. Results showed that biomass and oil content obtained were comparable to controls, indicating a successful metabolic-based pH control by the addition of carbonates in the ammonium-based media. Furthermore, FAME analysis revealed different profiles depending on the source of carbon used. Overall, this study suggests that integrating both types of NET strategies can contribute to the reduction of carbon emissions while producing biomass that can be further processed to generate a variety of bioproducts.

Combined effects of P25 TiO2 nanoparticles and disposable face mask leachate on microalgae Scenedesmus obliquus: analysing the effects of heavy metals.

Disposable surgical face masks extensively used during the COVID-19 outbreak would release microplastics into the aquatic environment. The increasing usage of titanium dioxide nanoparticles (nTiO2) in various consumer items has led to its ubiquitous presence in freshwater systems. This study determined the quantity and kind of microplastics discharged from disposable surgical face masks. The mask-leached microplastics were identified to be polypropylene of varying shapes and sizes, spanning from 1 μm to 15 μm. In addition, heavy metals like Cd, Cr, and Hg leached from the face masks were quantified. Four concentrations of nTiO2, 0.5, 1, 2, and 4 mg L-1, were mixed with leached solution from the face masks to perform the combined toxicity test on freshwater algae, Scenedesmus obliquus. A dose-dependent decrease in algal cell viability was observed upon treatment with various concentrations of nTiO2 individually. The mixtures of nTiO2 and the leached solution from the face masks exhibited significantly more toxicity in the algal cells than in their pristine forms. nTiO2 promoted increased production of oxidative stress and antioxidant enzyme activities resulting in cellular damage and decreased photosynthesis. These impacts were elevated when the algal cells were treated with the binary mixture. Furthermore, the heavy metal ions leached from face masks also contributed to the toxic effects. Our study shows that the leachates from disposable surgical face masks, combined with nTiO2, may pose a severe environmental threat.

Simultaneous bioremediation of Disperse orange-2RL Azo dye and fatty acids production by Scenedesmus obliquus cultured under mixotrophic and heterotrophic conditions

Several types of green photosynthetic microalgae can grow through the process of heterotrophic growth in the dark with the help of a carbon source instead of the usual light energy. Heterotrophic growth overcomes important limitations in the production of valuable products from microalgae, such as the reliance on light, which complicates the process, raises costs, and lowers the yield of potentially useful products. The present study was conducted to explore the potential growth of green microalga Scenedesmus obliquus under mixotrophic and heterotrophic conditions utilizing Disperse orange 2RL Azo dye as a carbon source to produce a high lipid content and the maximum dye removal percentage. After 7 days of algal growth with dye under mixotrophic and heterotrophic conditions with varying pH levels (5, 7, 9, and 11), KNO3 concentrations (1, 1.5, 2, and 3 g/L), and dye concentrations (20, 40, and 60 ppm); dye removal percentage, algal dry weight, and lipid content were determined. The results showed that the highest decolorization of Disperse orange 2RL Azo dye (98.14%) was attained by S. obliquus in heterotrophic medium supplemented with glucose at the optimal pH 11 when the nitrogen concentration was 1 g/L and the dye concentration was 20 ppm. FT-IR spectroscopy of the dye revealed differences in peaks position and intensity before and after algal treatment. S. obliquus has a high concentration of oleic acid, which is enhanced when it is grown with Disperse orange 2RL Azo dye, making it ideal for production of high-quality biodiesel. In general, and in the vast majority of instances, heterotrophic cultivation is substantially less expensive, easier to set up, and requires less maintenance than mixotrophic cultivation. Heterotrophic cultivation allows for large-scale applications such as separate or mixed wastewater treatment along with biofuel production.

Removal of tetracycline from water by catalytic photodegradation combined with the microalga Scenedesmus obliquus and the responses of algal photosynthesis and transcription

The antibiotic tetracycline (TC) and its degradation products (TDPs) in degradation solution present serious environmental problems, such as human health damage and ecological risk; thus further treatment is required before being released into the aquatic environment. Furthermore, their environmental impact on microalgae remains unclear. In this study, TC was degraded by photocatalysis using birnessite and UV irradiation, followed by biological purification using the microalga Scenedesmus obliquus. In addition, the photosynthetic activity and transcription of the microalgae were examined to evaluate the toxicity of TC and TDPs. The results show that photocatalytic degradation efficiency reached 92.7% after 30 min, and 11 intermediate products were detected. The microalgae achieved a high TC removal efficiency (99.7%) after 8 days. Exposure to the degraded TC solution (D) resulted in significantly lower (p < 0.05) biomass than the pure TC (T), and S. obliquus in the T treatment showed better resilience than the D treatment. Transcriptomic assays for different treatments revealed differential gene expression mainly involving the photosynthesis, ribosome, translation and peptide metabolic progresses. The up-regulation of photosynthesis-related genes and differential expression of chloroplast genes may be important for S. obliquus to acquire high photosynthetic efficiency and growth recovery when exposed to TC and TDPs. Our study provides a reference for TC removal using a combination of catalytic degradation and microalgal purification, and it is also helpful for understanding the environmental risk of TDPs in natural aquatic environments.

The comprehensive effects of aluminum oxide nanoparticles on the physiology of freshwater microalga Scenedesmus obliquus and it's phycoremediation performance for the removal of sulfacetamide

Nanoparticles are inevitable byproducts of modern industry. However, the environmental impacts arising from industrial applications of nanoparticles are largely under-reported. This study evaluated the ecotoxicological effects of aluminum oxide nanoparticles (Al2O3NP) and its influence on sulfacetamide (SA) biodegradation by a freshwater microalga, Scenedesmus obliquus. Although Al2O3NP showed limited toxicity effect on S. obliquus, we observed the toxicity attenuation aspect of Al2O3NP in a mixture of sulfacetamide on microalgae. The addition of 100 mg L−1 of Al2O3NP and 1 mg L−1 of SA reduced total chlorophyll by 23.3% and carotenoids by 21.6% in microalgal compared to control. The gene expression study demonstrated that ATPF0C, Lhcb1, HydA, and psbA genes responsible for ATP synthesis and the photosynthetic system were significantly downregulated, while the Tas gene, which plays a major role in biodegradation of organic xenobiotic chemicals, was significantly upregulated at 1 and 100 mg L−1 of Al2O3NP. The S. obliquus removed 16.8% of SA at 15 mg L−1 in 14 days. However, the removal was slightly enhanced (18.8%) at same concentration of SA in the presence of 50 mg L−1 Al2O3NP. This result proves the stability of sulfacetamide biodegradation capacity of S. obliquus in the presence of Al2O3NP co-contamination. The metabolic analysis showed that SA was degraded into simpler byproducts such as sulfacarbamide, sulfaguanidine, sulfanilamide, 4-(methyl sulfonyl)aniline, and N-hydroxy-benzenamine which have lower ecotoxicity than SA, demonstrating that the ecotoxicity of sulfacetamide has significantly decreased after the microalgal degradation, suggesting the environmental feasibility of microalgae-mediated wastewater technology. This study provides a deeper understanding of the impact of nanoparticles such as Al2O3NP on aquatic ecosystems.

Effects of Tetracycline on Scenedesmus obliquus Microalgae Photosynthetic Processes.

Tetracycline (TC) antibiotics can be detected worldwide in the aquatic environment due to their extensive use and low utilization efficiency, and they may affect the physiological processes of non-target organisms. In this study, the acute and sub-acute toxicities of TC on the freshwater microalga Scenedesmus obliquus were investigated with an emphasis on algal photosynthesis and transcription alterations during an 8 d TC exposure. The results showed that the IC10, IC30 and IC50 values were 1.8, 4.1 and 6.9 mg/L, respectively. During sub-acute exposure, the microalgae of the IC10 treatment was able to recover comparable growth to that of the control by day 7, while significantly lower cell densities were observed in the IC30 and IC50 treatments at the end of the exposure. The photosynthetic efficiency Fv/FM of S. obliquus first decreased as the TC concentration increased and then returned to a level close to that of the control on day 8, accompanied by an increase in photosynthetic activities, including light harvesting, electron transport and energy dissipation. Transcriptomic analysis of the IC10 treatment (1.8 mg/L TC) revealed that 2157 differentially expressed genes were up-regulated and 1629 were down-regulated compared with the control. KEGG and GO enrichments demonstrated that 28 photosynthesis-related genes involving light-harvesting chlorophyll protein complex, photosystem I, photosystem II, photosynthetic electron transport and enzymes were up-regulated, which may be the factor responsible for the enhanced photosynthesis and recovery of the microalgae. Our work may be helpful not only for gaining a better understanding of the environmental risk of TC at concentrations close to the real levels in natural waters, but also for explaining photosynthesis and related gene transcription induced by antibiotics.

Time-resolved transcriptome analysis of Scenedesmus obliquus HTB1 under 10% CO2 condition.

Certain microalgal species can grow under high CO2 concentrations providing potential for mitigating CO2 pollution in flue gas produced by power plants. Microalga Scenedesmus obliquus strain HTB1 was isolated from the Chesapeake Bay and grow rapidly in a high level of CO2 . However, little is known about the molecular responses of HTB1 to high CO2 levels. Here, we investigated how HTB1 responds to 10% CO2 using the time-resolved transcriptome analysis. Gene expression profiles indicated that HTB1 responds quickly (in 2 h) and becomes adaptive within 12 h when exposed to 10% CO2 . Interestingly, certain genes of light-harvesting, chlorophyll synthesis and carbon fixation (i.e. rbcS) were up-regulated at 10% CO2 , and these functional responses are consistent with the increased photosynthesis efficiency and algal biomass under 10% CO2 . Nitrate assimilation was strongly enhanced, with amino acid biosynthesis and aminoacyl tRNA biosynthesis genes being markedly up-regulated, indicating that HTB1 actively takes up nitrogen and accelerates protein synthesis at 10% CO2 . Carbon metabolism including fatty acid biosynthesis and TCA cycle was enhanced at 10% CO2 , supporting the earlier observation of increased lipid content of Scenedesmus sp. under high CO2 levels. Interestingly, key genes like RuBisCO (rbcL) and carbonic anhydrase in carboxysomes did not respond actively to 10% CO2 , implying that exposure to 10% CO2 has little impact on the carbon concentrating mechanisms and CO2 fixation of the Calvin cycle. It appears that HTB1 can grow rapidly at 10% CO2 without significant metabolic changes in carbon fixation and ATP synthesis.

Effects of Nitrogen and Phosphorus Concentrations on the Growth and Lipid Accumulation of Microalgae Scenedesmus obliquus

In the study, Scenedesmus obliquus green algae was cultivated under laboratory conditions at 21±2°C, 16:8 (light:dark) photoperiod and continuous aeration in different nitrogen and phosphorus ratio nutrient medium and its growth was determined. Dry weight, cell density (optical density) and chlorophyll a and b were used to determine the growth of the algae. The best growth was determined in the group consisting of 30 ml NaNO3+10 ml PO4. The amount of biomass obtained was determined as 1.549 gL-1 in this group. The lowest values were the group containing 5 ml NaNO3+5 ml PO4. With the decrease in the amount of nitrogen in the medium, an increase in the amount of carotene and a decrease in the amount of chl a and b were detected. The highest lipid values were determined as 36.7% in the group containing 5 ml NaNO3+5 ml PO4 and 36.2% in the group containing 5 ml NaNO3+10 ml PO4.

Enhancing biomass and lipid yield of microalga Scenedesmus obliquus by the periodic direct current

Nowadays, the disposal of municipal wastewater by microalgae while extracting microalgal high-value by-products has become an emerging trend. In this research, direct current electrochemical treatment was used to improve microalgae biomass production and wastewater treatment effect simultaneously. After electrochemical treatment, the cell number, biomass, chlorophyll-a content and lipid content of Scenedesmus obliquus cultivated in BG11 medium were significantly increased respectively by 13.1%, 32%, 9.7% and 30.1% at the 1.0 A/m2 direct current density. When Scenedesmus obliquus was cultured in real wastewater with electrochemical treatment at the 2.0 A/m2 direct current density, the biomass and lipid yield increased by 30.1% and 23.5%, respectively, while the removal of TP, ammonia and TN was also obviously accelerated. Therefore, the electrochemical cultivation of Scenedesmus obliquus offers good prospects for wastewater treatment and resource recycling.

Enhancing Biomass and Lipid Yield of Microalga Scenedesmus Obliquus by the Periodic Direct Current

Enhancing Biomass and Lipid Yield of Microalga Scenedesmus Obliquus by the Periodic Direct Current

Evaluation of the phycoremediation potential of microalgae for captan removal: Comprehensive analysis on toxicity, detoxification and antioxidants modulation

Captan is one of the most widely used organochlorine fungicides, its frequent application contaminates both terrestrial and aquatic ecosystems and negatively affects their key ecological processes. This study demonstrated the toxicity and efficient removal of captan by two different taxonomic species; the green microalga Scenedesmus obliquus and cyanobacterium Nostoc muscorum. After a week of exposure to mild (15 mg/L) and severe (30 mg/L) captan doses, the intracellular captan uptake, degradation and metabolic regulation of captan detoxification were studied. Compared to N. muscorum, S. obliquus accumulated more captan, but efficiently degraded it into two safe eco-friendly by-products; phthalic acid and 1,2,3,6-tetrahydro phthalimide. S. obliquus showed less decrease in cell growth, photosynthesis activity and related parameters including Chla content and activity of PEPC and RuBisCo enzymes. Captan at the severe dose induced oxidative damage particularly in N. muscorum, as expressed by the high levels of H2O2, MDA, NADPH oxidase and protein peroxidation. Both species invested glutathione-s-transferase enzyme in captan detoxification however, induction of antioxidant defence system e.g. ascorbate and glutathione cycle was more pronounced in S. obliquus which could explain its tolerance ability. This study provided a better understanding of the environmental risks of captan and introduced S. obliquus as a promising captan phycoremediator.