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The main goals of this study were to produce biodiesel from Scenedesmus obliquus algae using n-butanol as a green fuel and to analyse engine performance, combustion characteristics, and emission. Researchers are looking into how N-butanol affects mixes of Scenedesmus obliquus algae used to make biodiesel for use in Common Rail Direct Injection (CRDI) engines. In the studies, different combinations of Scenedesmus obliquus diesel algae were employed: 30 A (Algae), 30 A + 10% N-Butanol, 30 A + 20% N-Butanol, and 30 A + 30% N-Butanol. The pure 100% Diesel (D100) combination was also used. The butanol blends 30 A + 30% N and 30 A + 10% N both exhibit mediocre performance across the board in terms of emissions and combustion. When compared to pure diesel (D100), the ideal addition was 30 A + 20% N - Butanol, which led to a 10.96% gain in brake thermal efficiency and a 7.4% decrease in specific fuel consumption. On the other hand, because of the high concentration of D100 and the noticeable rise in exhaust temperature, there was an increase in nitrogen oxides in the exhaust gases. On the other hand, the exhaust gases concentrations of carbon monoxide and smoke opacity decreased by 19.2%, and 15%, respectively, in contrast to D100. Hydrocarbon emissions, on the other hand, dropped by 8%. The cylinder pressure and heat release rate improved by 8.6% and 36.43%, respectively, according to the combustion characteristic analysis results.

This study investigates the potential of two algae species from different genera, namely the recently isolated Scenedesmus obliquus BGP and Porphyridium cruentum, from the perspective of their integral sustainable transformation to valuable substances. Conventional Soxhlet and environmentally friendly supercritical fluid extraction were applied to recover oils from the species. The extracts were characterized through analytical techniques, such as GC-Fid and LC-MS/MS, which allowed their qualitative and quantitative differentiation. Thus, P. cruentum oils contained up to 43% C20:4 and C20:5 fatty acids, while those of S. obliquus BGP had only residual amounts. The LC-MS/MS analysis of phenolic compounds in the S. obliquus BGP and P. cruentum extracts showed higher content of 3-OH-4-methoxybenzoic acid and kaempferol 3-O-glycoside in the former and higher amounts of ferulic acid in the latter. Total phenolic content and antioxidant activity of the oils were also determined and compared. The compositional analysis of the oil extracts revealed significant differences and varying potentialities based on their genera and method of extraction. To the best of our knowledge our work is unique in providing such detailed information about the transformation prospects of the two algae species to high-value chemicals and bioproducts.

In recent years, the prospective use of algae as an alternate fuel source for petroleum-based fuels has increased drastically. It has been researched extensively and proven that it can be used as a sustainable feedstock for producing green energy considering environmental safety. This article focused on the economically viable algal feedstock for the production of lipid content for its use as a feedstock for biodiesel production. For this purpose, the algal species Scenedesmus obliquus and Chlorella vulgaris were selected, and it was grown under lab and open ambient conditions with two Blue green Medium (BG-11) and Bold Basal medium (BBM). Upon the yield, it was noticed that the BG-11 medium gave optimum lipid yield for both species. Hence, it was determined that through this medium higher lipid yield can be expected, and based on the GC-MS result it was notified that it can be a viable source of alternate fuel.

Ag nanoclusters (AgNCs) have gained widespread applications in recent years due to their excellent antimicrobial efficacy and distinctive molecule-like characteristics. However, concerns about their potential effects on environmental and human health have been raised. Despite the fact that abundant research has been carried out to examine the possible ecotoxicology of AgNCs in a variety of living organisms, these studies have mostly concentrated on the toxicology of individual organisms and only a few have attempted to look into the impact of AgNCs across the aquatic food chain. This work evaluated the transcriptome level genotoxicity of AgNCs and their degraded Ag ions in two model species food chains: the aquatic green algae Scenedesmus obliquus and the invertebrate Daphnia magna. Daphnia magna’s digestive system and glycerophospholipid metabolism were hindered after feeding on Ag-containing algae as a result of down-regulation of the crucial gene PLA2G(SPLA2) that codes for secretory phospholipase A2. Our research also showed that the genotoxicity of AgNCs to Daphnia magna was mediated by a synergic interaction between the particulate form of AgNCs and their degraded Ag ions. The current work offers a fresh viewpoint on the mechanisms underlying AgNCs’ harmful effects and the possible ecological concern that metal-based nanoparticles provide to aquatic life.

Open-field burning of rice straw contributes significantly to deterioration of air quality. Similarly, defatted algal residue is a surplus by-product of the algal biofuel industry. This study emphasizes on the two-step conversion of agro-industrial residues (rice straw and Scenedesmus obliquus deoiled biomass) into biodiesel and carotenoids using oleaginous red yeast Rhodotorula mucilaginosa R2. The effect of biological pretreatment on degradation of lignocellulosic substrates followed by catalytic saccharification was evaluated using suitable analytical techniques. Mixed biomass favoured the growth and secretion of extracellular cellulose degrading enzymes by Penicillium citrinum PKB20 resulting in the highest specific activity of endoglucanase (83.02 IU/mg), xylanase (103 IU/mg) and β-glucosidase (13.8 IU/mg) under solid-state fermentation. The hydrolysis of pre-treated substrate was achieved with a saccharification yield of 41.41 %. Batch fermentation of detoxified hydrolysate amended with synthetic yeast propagation or lipid production media (YEPD or C/N 75) resulted in maximum lipid content and lipid yield of 30.43 % and 1.19 g/L respectively. GC analysis revealed that oleic acid (29.4-50.39 %) was the predominant fatty acid. The crude carotenoid extract was composed of torularhodin, torulene and β-carotene and exhibited strong antioxidant activity. Graphic Abstract

Carbon nanotubes (CNTs), α-Fe 2 O 3 nanoparticles (nano Fe 2 O 3 ) and MgO nanoparticles (nano MgO) were evaluated for the effects on algae growth and lipid production. Nano Fe 2 O 3 promoted cell growth in the range of 0–20 mg·L −1 . CNTs, nano Fe 2 O 3 and nano MgO inhibited cell growth of Scenedesmus obliquus at 10, 40 and 0.8 mg·L −1 respectively. Neutral lipid and total lipid content increased with the increasing concentration of all tested nanoparticles. The maximum lipid productivity of cultures exposed to CNTs, nano Fe 2 O 3 and nano MgO was observed at 5 mg·L −1 , 5 mg·L −1 and 40 mg·L −1 , with the improvement by 8.9%, 39.6% and 18.5%. High dose exposure to nanoparticles limited increase in lipid productivity, possibly due to the repression on cell growth caused by nanoparticles-catalyzed reactive oxygen species (ROS) generation, finally leading to reduction in biomass and lipid production. Reduced accumulation of fatty acids of C18:3n3, C18:3n6 and C20:2 was observed in cells exposed to nanoparticles.

The increase in worldwide water contamination with numerous pharmaceutical contaminants (PCs) has become an emerging environmental concern due to their considerable ecotoxicities and associated health issues. Microalgae-mediated bioremediation of PCs has recently gained scientific attention, as microalgal bioremediation is a solar-power driven, ecologically comprehensive, and sustainable reclamation strategy. In this review, we comprehensively describe the current research on the possible roles and applications of microalgae for removing PCs from aqueous media. We summarize several novel approaches including constructing microbial consortia, acclimation, and cometabolism for enhanced removal of PCs by microalgae, which would improve practical feasibility of these technologies. Some novel concepts for degrading PCs using integrated processes and genetic modifications to realize algal-based bioremediation technologies are also recommended. Water contamination with numerous pharmaceutical contaminants (PCs) has been one of the most important emerging environmental problems facing humanity due to their ecotoxicities and health issues. Culturing microalgae in wastewater can create a ‘zero-waste concept’ and stimulate an effective and sustainable practice for the microalgae biofuel industry. Constructing microbial consortia, acclimating microorganisms, and cometabolic approaches can improve the engineering feasibility of microalgae-based biotechnologies. Some innovative concepts, such as integrated processes (algae-based technologies with advanced oxidation processes, constructed wetlands, and microbial fuel cells) and genetic modifications, can help to realize algae-based bioremediation technologies.

Microalgae are microorganisms with the capacity to contribute to the sustainable and healthy food production, in addition to wastewater treatment. The subject of this work was to determine the potential of Scenedesmus obliquus microalga grown in brewery wastewater to act as a plant biostimulant. The germination index of watercress seeds, as well as the auxin-like activity in mung bean and cucumber, and in the cytokinin-like activity in cucumber bioassays were used to evaluate the biostimulant potential. Several biomass processes were studied, such as centrifugation, ultrasonication and enzymatic hydrolysis, as well as the final concentration of microalgal extracts to determine their influence in the biostimulant activity of the Scenedesmus biomass. The results showed an increase of 40% on the germination index when using the biomass at 0.1 g/L, without any pre-treatment. For auxin-like activity, the best results (up to 60% with respect to control) were obtained at 0.5 g/L of biomass extract, after a combination of cell disruption, enzymatic hydrolysis and centrifugation. For cytokinin-like activity, the best results (up to 187.5% with respect to control) were achieved without cell disruption, after enzymatic hydrolysis and centrifugation at a biomass extract concentration of 2 g/L.

Background Cultivation of microalgae in wastewater could significantly contribute to wastewater treatment, biodiesel production, and thus the transition to renewable energy. However, more information on effects of environmental factors, including light intensity, on their growth and composition (particularly fatty acid contents) is required. Therefore, we investigated the biomass and fatty acid production of four microalgal species, isolated in the Northern hemisphere and grown at three light intensities (50, 150 and 300 μE m−2 s−1). Results Increases in light intensities resulted in higher biomass of all four species and, importantly, raised fatty acid contents of both Desmodesmus sp. and Scenedesmus obliquus. Fourier-transform IR spectrometry analysis showed that the increases in fatty acid content were associated with reductions in protein, but not carbohydrate, contents. Assessment of fatty acid composition revealed that increasing light intensity led to higher and lower contents of oleic (18:1) and linolenic (18:3) acids, respectively. The microalgae consumed more than 75% of the nitrogen and phosphorus present in the wastewater used as growth medium. Conclusion The results show the importance of optimizing light intensities to improve fatty acid production by microalgae and their quality as sources of biodiesel. In addition, increase in fatty acid content is associated with decrease in protein content.

The demand for sustainable and environmentally friendly food sources and food ingredients is increasing, and microalgae are promoted as a sustainable source of essential and bioactive lipids, with high levels of omega-3 fatty acids (ω-3 FA), comparable to those of fish. However, most FA screening studies on algae are scattered or use different methodologies, preventing a true comparison of its content between microalgae. In this work, we used gas-chromatography mass-spectrometry (GC-MS) to characterize the FA profile of seven different commercial microalgae with biotechnological applications (Chlorella vulgaris, Chlorococcum amblystomatis, Scenedesmus obliquus, Tetraselmis chui, Phaeodactylum tricornutum, Spirulina sp., and Nannochloropsis oceanica). Screening for antioxidant activity was also performed to understand the relationship between FA profile and bioactivity. Microalgae exhibited specific FA profiles with a different composition, namely in the ω-3 FA profile, but with species of the same phylum showing similar tendencies. The different lipid extracts showed similar antioxidant activities, but with a low activity of the extracts of Nannochloropsis oceanica. Overall, this study provides a direct comparison of FA profiles between microalgae species, supporting the role of these species as alternative, sustainable, and healthy sources of essential lipids.