Green Microalga Scenedesmus Obliquus Research Articles

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.

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.

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.

Improved lipid productivity of Scenedesmus obliquus with high nutrient removal efficiency by mixotrophic cultivation in actual municipal wastewater

This study was aimed to assess the growth and lipid productivity improvement of a green microalga Scenedesmus obliquus by mixotrophic cultivation, via addition of sodium acetate (NaAc) into actual municipal wastewater (AMW). Moreover, the nutrient removal efficiency of the culture media in terms of carbon, nitrogen, and phosphorus was investigated. The results showed that the S. obliquus grew better in the AMW than in the BG11 medium (0.20 g L−1 vs 0.16 g L−1 in dry cell weight), and the final algal lipid productivity was higher (9.02 mg L−1 d−1 vs 7.75 mg L−1 d−1, P < 0.05). Further, the addition of NaAc significantly stimulated the algal growth and lipid productivity. Specifically, the highest improvement was obtained by the NaAc-addition of 1 g L−1, where the algal dry cell weight increased 2.40 times than that in the AMW with little organic carbon (0.48 mg L−1 vs 0.20 mg L−1, P < 0.01), and the corresponding algal lipid productivity increased 2.44 time (22.08 mg L−1 d−1 vs 9.02 mg L−1 d−1, P < 0.01). Meanwhile, the addition of 1 g L−1 of NaAc significantly increased the microalga-driven nitrogen and phosphorus removal efficiency, respectively by 1.75 and 2.23 times (82.20% vs 46.85% for total nitrogen, and 76.35% vs 34.18% for total phosphorus). In summary, this study confirmed the feasibility of using organic carbon-supplemented AMW to replace the artificial media for microalgae-based lipid production and nutrient recycling.

Effects of Sulfur Starvation on Growth Rates, Biomass and Lipid Contents in the Green Microalga Scenedesmus obliquus.

Scenedesmus obliquus, a green unicellular chlorophycean microalga, is well-established as a lipid and biomass production platform. The nutrient starvation strategy is considered as a robust platform for lipid production from different microalgal strains. The study aimed to analyse the influences of sulfur starvation on the growth rates, and also biomass and lipid production and composition in a naturally isolated strain of S. obliquus. The BG-11 culture medium was utilized for preservation and microalgal growth. To monitor the cell growth rates, two different methods, including direct cell counting and also dry cell weight measurement were used. The study was conducted in 28 days composed of two distinct growth modes as 10 days of sulfur-rich and 18 days of sulfur starved media. The studied S. obliquus strain displayed higher lipid and carbohydrate production levels (34.68% and 34.02%) in sulfur starved medium compared with the sulfur-rich medium (25.84% and 29.08%). Nevertheless, a noticeable reduction (51.36%) in biomass contents and also in cell growth rates (63.36%) was observed during sulfur starvation. The investigated strain was composed of some important fatty acids with potential applications as food, feed and biodiesel. The observed results implied the possibility of the sulfur starvation strategy to increase lipid production in S. obliquus strain. Besides, the available data from recently published patents reveals the promising potential of the identified lipids from S. obliquus in this study for bioenergy production and other biotechnological purposes.

Green Microalgae Scenedesmus Obliquus Utilization for the Adsorptive Removal of Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) from Water Samples.

In view of the valorisation of the green microalga Scenedesmus obliquus biomass, it was used for the biosorption of two nonsteroidal anti-inflammatory drugs, namely salicylic acid and ibuprofen, from water. Microalgae biomass was characterized, namely by the determination of the point of zero charge (pHPZC), by Fourier transform infrared (FT-IR) analysis, simultaneous thermal analysis (STA) and scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS). Kinetic and equilibrium batch experiments were carried out and results were found to fit the pseudo-second order equation and the Langmuir isotherm model, respectively. The Langmuir maximum capacity determined for salicylic acid (63 mg g−1) was larger than for ibuprofen (12 mg g−1), which was also verified for a commercial activated carbon used as reference (with capacities of 250 and 147 mg g−1, respectively). For both pharmaceuticals, the determination of thermodynamic parameters allowed us to infer that adsorption onto microalgae biomass was spontaneous, favourable and exothermic. Furthermore, based on the biomass characterization after adsorption and energy associated with the process, it was deduced that the removal of salicylic acid and ibuprofen by Scenedesmus obliquus biomass occurred by physical interaction.

Insights into the effect of cerium oxide nanoparticle on microalgal degradation of sulfonamides

Nanoparticles have been commercially used worldwide; however, there is a lack of information of their environmental impacts and ecotoxicity. In this study, the effect of cerium oxide nanoparticle (CeO2NP) on a green microalga Scenedesmus obliquus, and microalgal biodegradation of four sulfonamides (sulfamethazine, sulfamethoxazole, sulfadiazine, and sulfamethoxazole) was investigated. There is insignificant inhibition of microalgal growth induced by CeO2NP; however, it substantially influenced the expression of genes involved in key cellular metabolic activities of S. obliquus. For example, genes involved in photosynthetic activity (psbA) and energy production (ATPF0C) were downregulated with exposure to CeO2NP. The low concentrations of CeO2NP improved microalgal degradation of sulfonamides. This may be because of the upregulated genes encoding hydrogenase and oxidoreductase. The exploration of this study has provided a new understanding of the environmental impacts of CeO2NP on microalgae-based biotechnologies for treatment of wastewater containing emerging organic contaminants.

Ecotoxicological response of Scenedesmus obliquus to pure energetic compounds and metal ions found in wastewater streams from munitions manufacturing

The energetic compounds 1-methoxy-2,4-dinitrobenzene (DNAN), nitroguanidine (NQ), 3-nitro-1,2,4-triazole-5-one (NTO) and 1,3,5-trinitro-1,3,5-triazinane (Research Department Explosive, RDX) are widely used for explosive formulations production. Wastewater streams from industrial munition facilities are rich in nitrogen and contain considerable amounts of residual energetic compounds and metals such as zinc, nickel and copper. As such, these wastewater streams require physicochemical and/or biological treatment to meet regulatory discharge limits. The high nitrogen content of these streams makes them an attractive nutrient source for growing biomass such as microalgae. In previous studies we have identified some wastewater streams suitable for microalgal growth with minimal or no prior treatment, while others have shown moderate to high growth inhibition. The current study aims to elucidate the toxicity response of microalgae by performing growth-inhibition assays using solutions of single compounds and mixtures of energetic compounds and heavy metals. Using the freshwater green microalga Scenedesmus obliquus (S. obliquus) (ATCC® 11477) as a model organism, a microwell-plate growth-inhibition test procedure was performed to assess potential growth inhibition effects by DNAN, NQ, NTO, RDX, Zn, Ni and Cu. For the three metals tested, the order of growth rate inhibition effect on S. obliquus was Ni > Cu > Zn. The EC50s of Ni, Cu and Zn for S. obliquus were 0.08 mg/L, 0.26 mg/L and 10.13 mg/L, respectively. The effective concentrations for 50% growth inhibition (EC50) were 4.86 mg/L for DNAN and 8,700 mg/L for NTO. Conversely, RDX exhibited no toxicity below its solubility limit, and NQ had a mild toxic effect on S. obliquus with an EC20 of 303.3 mg/L.

Effect of trace metals on growth performance and accumulation of lipids, proteins, and carbohydrates on the green microalga Scenedesmus obliquus

Microalgae biomass is considered one of the most promising raw materials for the development of high commercial value products, mainly because they are potential sources of proteins, lipids, carbohydrates, and vitamins. In this way, the optimization of culture medium of these microorganisms can help to reduce production costs, making final products more accessible. In this sense, the present study aimed to investigate the effect of different trace metal concentrations on growth and biochemical composition of Scenedesmus obliquus. Cultures of S. obliquus were performed using the LCA-AD medium (pH 7.6), in 2-L cylindrical borosilicate glass flasks that were constantly stirred by bubbling 0.7% CO2 enriched air (v/v), irradiance ranging from 520 to 1200 μmols m−2 s−1, and temperature at 22 ± 1 °C. Four trace metal concentrations were tested: control (standard concentration used on Bold’s Basal Medium), ten (10−1), hundred (10−2), and thousand (10−3) times less than control. The trace metal concentration did not significantly affect the growth of S. obliquus – all treatments have reached about 4.2 g L−1 on the tenth day of cultivation. As well for growth performance, no significant differences were observed among the treatments for biomass composition percentages. The dry S. obliquus biomass was mainly composed of carbohydrates (about 65%), crude protein (about 20%), and finally lipids (about 12%). These findings suggest that up to 1000-fold reduction in trace metal concentration does not affect the growth and biochemical composition of the green microalga S. obliquus.

A comparison of harvesting and drying methodologies on fatty acids composition of the green microalga Scenedesmus obliquus

Harvesting and drying processes are still obstacles in the microalgae production chain. In this study, a combination of different harvesting and drying methods for Scenedesmus obliquus was proposed. S. obliquus was cultivated in a pond raceway for 15 days until reaching stationary phase. The culture was separated by different harvesting methods (centrifugation and flocculation) and drying methods (freezing, freeze-drying and oven drying), each combination in triplicate. Flocculation did not influence FAME yield of S. obliquus, except when the biomass was dried in an oven. The biomass that was only frozen had the lowest FAME content due to the presence of reactive water in the biomass. In contrast, frozen biomass had higher content of saturated and monosaturated fatty acids; freeze-drying or oven drying caused an enrichment of the polyunsaturated fatty acids content. In conclusion, if the biomass will be used to extract polyunsaturated fatty acids, freeze-drying would be more appropriate. On the other hand, if the purpose of the biomass is to produce biodiesel, the best process would be to just freeze the biomass.

Enhanced yield of Scenedesmus obliquus biomacromolecules through medium optimization and development of microalgae based functional chocolate.

The freshwater green microalga Scenedesmus obliquus was cultivated to enhance the contents of proteins, carbohydrates and lipids by using Box-Behnken experimental design. S. obliquus was cultured under phototrophic conditions by using Bold's Basal Medium with different cultivation parameters including pH (7, 8 and 9), salinity (10, 30 and 50mM), and nitrogen source (0.125, 0.5 and 1g/L). The highest biomass yield (64.9 ± 0.94mg/L/day) was obtained by using optimized medium at a salinity concentration of 30mM (w/v), and nitrogen sources of 0.125g/L. The maximum content of protein, lipid and carbohydrates from S. obliquus optimized medium were 342.19 ± 0.28mg/g, 241.41 ± 4.32mg/g and 288.05 ± 1.12mg/g of dry wt. respectively. The amino acid and fatty acid analysis of S. obliquus biomass indicated the presence of significant amount of essential amino acids and essential fatty acids. Furthermore, chocolate crispy bar was developed by fortification with encapsulated freeze-dried S. obliquus and evaluated for its oxidative stability and sensory analysis. The chocolate fortified with microalgae can be a potential source of essential fatty acids and amino acids in addition to other bioactive compounds.

Night illumination using monochromatic light-emitting diodes for enhanced microalgal growth and biodiesel production

The present study investigated the effect of monochromatic light-emitting diodes (LEDs) on the growth and biodiesel yield of the green microalga Scenedesmus obliquus. Different LEDs were applied individually or in combination during the night period. Among different individual treatments, red and blue illumination showed the highest biomass and lipid productivity due to stimulation of pigmentation and photosystem II, respectively. Microalgal growth, lipid production and biodiesel recovery significantly increased under combined blue-red illumination. In addition, saturated and monounsaturated fatty acids proportions increased in favor of polyunsaturated ones. Moreover, blue-red LEDs enhanced the net biodiesel energy output over the control. The total increase in net energy output represented 5.1, 3.8 and 10.8 MJ using red, blue and blue-red light, respectively. In conclusion, application of blue-red LEDs during the night period is an economical technology for microalgae cultivation, which might have a potential impact on the future of commercial biodiesel production from microalgae.

Influence of Nitrogen Source and Growth Phase on Extracellular Biosynthesis of Silver Nanoparticles Using Cultural Filtrates of Scenedesmus obliquus

In this study, silver nanoparticles (AgNPs) were green-synthesized extracellularly by the action of bioactive compounds in cultural filtrates of green microalga Scenedesmus obliquus (KY621475). The influences of six different nitrogen sources (i.e., NaNO3, CO(NH4)2, (NH4)2CO3, KNO3, NH4NO3, and (NH4)2SO4) on extracellular biosynthesis of AgNPs were observed by UV–Visible spectroscopy (380–425 nm) and confirmed using high-resolution transmission electron microscopy (HRTEM). The highest biomass production was observed in the case of urea and ammonium carbonate treatments, which, surprisingly, showed negative activity for AgNPs biosynthesis. Considering their coupling and compatible presence in cultural filtrates, reductases (especially nitrate reductase) as reduction agents are assumed to play a key role in the extracellular biosynthesis of AgNPs. The cultural filtrates of the potassium and sodium nitrate treatments produce AgNPs of relatively small size (5–10 and 4–10 nm, respectively), smaller than those produced by filtrate of ammonium nitrate treatment. The antimicrobial activity of produced AgNPs was a function mainly of particle size, which was influenced by the nitrogen source of the microalgal culture. The AgNPs produced from the KNO3 and NaNO3 cultural filtrates performed the best as antimicrobial agents.

Optimization of microwave assisted lipid extraction from microalga Scenedesmus obliquus grown on municipal wastewater

Efficient cost effective lipid extraction from microalgae is a challenging topic for large scale production of microalgae-based biodiesel. In this study, a microwave-assisted lipid extraction process was applied to the oil-rich green microalga Scenedesmus obliquus grown on municipal wastewater. N-hexane/isopropanol solvent was used as alternative solvent. Optimal extraction parameters were determined as: operational temperature of 130 °C, extraction time of 0.25 h, solvent ratio of N-hexane/isopropanol of 3:2 (V:V), phase ratio of co-solvent/biomass was 50:1 (mL:g). Relative extraction rates of lipid and fatty acid methyl esters (FAMEs) achieved using microwave-assisted extraction (MAE) were 88.25% and 95.58%, respectively, which is higher than traditional water bath heating extraction process (WHE). In addition, compared with WHE, the apparent first order rate constant of MAE was enhanced by 18 times compared to traditional methods. Analysis using scanning electron microscopy indicated that disruption of the cell wall of Scenedesmus obliquus by microwave led to the enhancement of solvents’ penetration and lipid extraction.

Growth modeling of the green microalga Scenedesmus obliquus in a hybrid photobioreactor as a practical tool to understand both physical and biochemical phenomena in play during algae cultivation.

In recent years, numerous studies have justified the use of microalgae as a sustainable alternative for the generation of different types of fuels, food supplementation, and cosmetics, as well as bioremediation processes. To improve the cost/benefit ratio of microalgae mass production, many culture systems have been built and upgraded. Mathematical modeling the growth of different species in different systems has become an efficient and practical tool to understand both physical and biochemical phenomena in play during algae cultivation. In addition, growth modeling can guide design changes that lead to process optimization. In the present work, growth of the green microalga Scenedesmus obliquus was modeled in a hybrid photobioreactor that combines the characteristics of tubular photobioreactors (TPB) with thin-layer cascades (TLC). The system showed productivity greater than 8.0 g m-2 day-1 (dry mass) for CO2 -fed cultures, and the model proved to be an accurate representation of experimental data with R2 greater than 0.7 for all cases under variable conditions of temperature and irradiance to determine subsystem efficiency. Growth modeling also allowed growth prediction relative to the operating conditions of TLC, making it useful for estimating the system given other irradiance and temperature conditions, as well as other microalgae species.

Optimization of chemical flocculation of Scenedesmus obliquus grown on municipal wastewater for improved biodiesel recovery

Cost-efficient harvesting of microalgae is a major challenge for large-scale biomass production. The present study aimed to optimize and model the flocculation process for efficient harvest of the biodiesel promising green microalga Scenedesmus obliquus grown in municipal wastewater. In addition, the influence of applied flocculation on biodiesel recovery was measured. Ferric sulphate showed the highest relative flocculation efficiency in comparison with the other tested flocculants. At initial OD680 of 1, the flocculent dose required to achieve 99.5% flocculation efficiency was 150 mg L−1 after 40 min. In addition, relatively higher flocculation efficiencies of S. obliquus cells were observed at lower initial OD680. The suggested polynomial model showed satisfactory and accurate results, with high positive correlation (0.956) between the calculated and measured flocculation efficiency. Furthermore, fatty acid methyl esters (FAMEs) yield of the flocculated biomass showed 40.9% significant increase (P < 0.01) over the centrifuged cells. It can be concluded that flocculation using ferric sulphate is greatly advantageous, as in a single step it served a dual propose of algal biomass harvest and enhanced FAMEs recovery at doses much lower than that used in wastewater treatment plants.

Production and characterization of biodiesel from the unicellular green alga Scenedesmus obliquus

ABSTRACTRegardless of whether biodiesel is represented in the form of oil from grains, agricultural crops, or microorganisms, it is a clean fuel depends mainly on biomass conversion. The present work indicates that the green microalga Scenedesmus obliquus showed higher biomass productivity of 0.15 g (CDW) L−1 d−1. The increase in NaCl concentration up to +100% caused an increase in growth, esterified fatty acid (EFA) content, and EFA productivity of S. obliquus. The decrease or increase of pH values reduced the growth, EFA content, and productivity. Biomass productivity increased from 0.06 g L−1d−1 under a light intensity of 80 μmol m−2s−1 to 0.1 g L−1d−1 at 160 μmol m−2 s−1. Biodiesel characterization showed that the iodine value of biodiesel of S. obliquus was 70 g iodine/100 g oil. Except viscosity, all biodiesel characteristics are in accordance with the European standards for fuel diesel (EN 590:1999). These results nominate S. obliquus as a promising candidate for biodiesel production by outdoor cultivation.

Biosorptive removal of basic dye methylene blue using raw and CaCl2 treated biomass of green microalga Scenedesmus obliquus

Biosorptive removal of basic dye methylene blue using raw and CaCl2 treated biomass of green microalga Scenedesmus obliquus

Effect of flue gas CO2 on the growth, carbohydrate and fatty acid composition of a green microalga Scenedesmus obliquus for biofuel production

ABSTRACT Effect of various flue gas CO2 concentrations (5%, 10% and 14.1%) on growth rate and biochemical properties of a green microalga Scenedesmus obliquus was investigated. S. obliquus showed the highest biomass production and growth rate (0.36 g L−1 and μ max = 1.00 day−1), total inorganic carbon removal (35.8 mg L−1), lipid productivity (9.9 mg L−1 day) and carbohydrate productivity (10.3 mg L−1 day) with 14.1% CO2 after 8 days of cultivation. Fatty acid methyl ester analysis revealed that the palmitic and oleic acid contents were increased up to 5% and 7% with 14.1% CO2, respectively. Application of flue gas CO2 enhanced the growth along with lipid and carbohydrate productivity of S. obliquus, which can be exploited for reducing the CO2 concentration.

Mixotrophic cultivation of a microalga Scenedesmus obliquus in municipal wastewater supplemented with food wastewater and flue gas CO2 for biomass production

The biomass and lipid/carbohydrate production by a green microalga Scenedesmus obliquus under mixotrophic condition using food wastewater and flue gas CO2 with municipal wastewater was investigated. Different dilution ratios (0.5–2%) of municipal wastewater with food wastewater were evaluated in the presence of 5, 10 and 14.1% CO2. The food wastewater (0.5–1%) with 10–14.1% CO2 supported the highest growth (0.42–0.44 g L−1), nutrient removal (21–22 mg TN L−1), lipid productivity (10–11 mg L−1day−1) and carbohydrate productivity (13–16 mg L−1day−1) by S. obliquus after 6 days of cultivation. Food wastewater increased the palmitic and oleic acid contents up to 8 and 6%, respectively. Thus, application of food wastewater and flue gas CO2 can be employed for enhancement of growth, lipid/carbohydrate productivity and wastewater treatment efficiency of S. obliquus under mixotrophic condition, which can lead to development of a cost effective strategy for microalgal biomass production.