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The continued search and urgent need for renewable fuel sources have necessitated the exploration of microalgae to identify relevant species for making biofuels. The aim of the study was bioprospecting and screening native microalgae strains from freshwater habitats of the Almaty region, Kazakhstan, to assess the potential for producing biofuel. The studied strains demonstrated simultaneous biomass productivity, lipid productivity, suitable fatty acid composition, and biodiesel properties. The sequence analysis of the ribosomal DNA internal transcribed spacer partial region and ribulose-bisphosphate carboxylase gene (rbcL) led to the identification of five microalgae: Monoraphidium griffithii ZBD-01, Nephrochlamys subsolitaria ZBD-02, Ankistrodesmus falcatus ZBD-03, Parachlorella kessleri ZBD-04, and Desmodesmus pannonicus ZBD-05. P. kessleri had the highest biomass production (1.42 ± 0.08 g L−1 day−1), lipid productivity (29 ± 1.2 g L−1day−1), and C 16 –C 18 fatty acid contents (90%), followed by A. falcatus and M. griffithi. Gas chromatography/mass spectrometry analysis indicated that the dominant fatty acids in these strains were palmitic, stearic, and oleic acids. The calculated biodiesel properties of P. kessleri and A. falcatus based on fatty acid methyl esters (FAME) profiles showed relatively good fuel properties (cetane numbers - 48 and 50; iodine and saponification values - 83.4 and 103.6 g I₂/100 g oil, 260.8 and 199.5 mg KOH g−1), which correlate well with. Our results suggest that P. kessleri and A. falcatus are promising strains for biodiesel production due to their high lipid productivity, fatty acid profile with relatively high content of oleic acid, and suitable biodiesel properties. The isolated native species of microalgae from natural freshwater bodies of the Almaty region present opportunities for further exploitation for the sustainable production of biomass and biodiesel. [Display omitted] · New native strains of green microalgae were isolated and identified. · Fatty acids composition of microalgae strains was investigated. · Microalgae strains found enriched with saturated fatty acids (C16:0 and C18:0). · These strains are the best candidate for application in biofuel. [ABSTRACT FROM AUTHOR]

Five axenic cultures of microalgae were isolated from the wastewater of Almaty city and identified as Chlorella vulgaris strain № 1, Chlorella sp. strain № 3, Scenedesmus obliquus , Phormidium foveolarum and Lyngbya limnetica . Among these strains, C. vulgaris strain № 1 was characterized by the maximum growth rate and the highest productivity. Mass cultivation of this strain in wastewater resulted in accumulation of 5 × 10 7 cells per ml in 16 days, and in the removal of ∼95% of pollutants from water. Cells of C. vulgaris consisted of ∼35% proteins, 29% carbohydrates, 30% lipids, and 6% ash, as calculated on a dry weight basis. The major fatty-acids of C. vulgaris were represented by palmitic, cis -7,10-hexadecenoic acid, linoleic, and α-linolenic acids. Culturing in wastewater decreased the unsaturation index of FAs. Thus, C. vulgaris cells are suitable for both waste water purification and accumulation of biomass for further biodiesel production. [ABSTRACT FROM AUTHOR]

Environmental and energy security has now become a serious global problem, requiring a lot of research to find and implement its cost-effective and environmentally friendly alternatives. The development and use of renewable energy sources is necessary and important in order to avoid the emergence of a global economic crisis. One of the solution to prevent a future crisis caused by energy shortages is to introduce biofuels into the fuel market. Despite the fact that various forms of renewable energy are currently used, the prospects for the production of biofuels from cyanobacteria are quite high due to their unique properties, such as a high lipid content and a suitable fatty acid (FA) composition for the production of biofuels, their suitability for growing open water and the ability to grow on wastewater. The purpose of this article is to provide a comprehensive overview of the potential of cyanobacteria in the conversion of wastewater into biofuels. The article covers comparative data on the accumulation of lipids and the content of fatty acids in various representatives of cyanobacteria and their possibilities in the remediation of wastewater. Various approaches to the extraction of lipids from phototrophic microorganisms that are currently available, their advantages and disadvantages, and the results of the monitoring of the main key points of the development of the technology for converting cyanobacterial biomass into biofuels, with an emphasis on the existing barriers, effects and solutions, are also considered. Further research in this field is required for the successful implementation of this technology on an industrial scale. [ABSTRACT FROM AUTHOR]

• The optimal concentration of CO 2 for cultivation of cyanobacterial strains was determined. • The optimal concentration of wastewater for cultivation of cyanobacteria was determined. • The fatty acid composition of lipids was studied. • The yield of dry biomass and methyl esters of Cyanobacterium sp. IPPAS B-1200 strain was determined. Current fresh water and energy shortage determines the need to study the possibilities of using living objects in bioenergy and environmental purification technologies. The development of waste-free technologies allows waste recycling, which saves raw materials and energy, in turn, reducing waste generation. The effect of different carbon dioxide concentrations and wastewater from households on the growth of cyanobacteria was studied in order to determine their capabilities in the purification processes. It was found that the optimal CO 2 concentration for the cultivation of cyanobacteria Cyanobacterium sp. IPPAS B-1200 and Desertifilum sp. IPPAS B-1220 was 10 %, and for the Cyanobacterium aponinum IPPAS B-1201 – 5%. It was revealed that the cultivation of the cyanobacterium Cyanobacterium sp. IPPASB-1200 on wastewater from the water storage reduces the concentration of organic pollutants and, accordingly, improves the physicochemical properties of water. The cleaning percentage for selected pollutants was 68–100 %. It was shown that the most optimal ratio of wastewater to nutrient media for cyanobacteria cultivation were 25:75 and 50:50. The lipid content (%/dry weight) in the biomass of the studied strains of cyanobacteria ranges from 15 to 22% after cultivation in wastewater. It was determined that the strains of Cyanobacterium genus were the most suitable for the production of biodiesel according to their fatty acids composition. It was determined that lipids were composed of only saturated and monounsaturated fatty acids. As a result of the studies, the optimal conditions for the growth of Cyanobacterium sp. IPPAS B-1200 were determined. This microorganism has a good potential to produce biodiesel as a producer of saturated and monounsaturated middle-chain-length fatty acids. [ABSTRACT FROM AUTHOR]

Abstract Biomass of high-yielding strains of phototrophic microorganisms actively accumulating lipids is a promising non-traditional raw material for bioenergy including the production of biodiesel. In this study, we present results of searching for new strains of microalgae-producers of lipids from hot springs. Within the framework of research, the primary screening of water for the presence of lipid - accumulative microalgae was carried out with the help of qualitative reaction with lipid-specific dyes, as well as 5 axenic isolates of microalgae with stable growth were identified in the laboratory and their productivity and fatty acid composition were studied. The isolated strains were identified as Chlorella vulgaris sp-1, Ankistrodesmus sp-21 , Scеnеdеsmus obliquus sp-21, Chlorella pyrenoidosa sp-13 and Chlamydomonas sp-22. The obtained data showed that the isolated strains determined by biomass in the range 1.3 g/l to 1.81 g/l. As a result of the research, it was established that the highest content of lipids was observed in the strains Chlorella vulgaris sp-1 and Scеnеdеsmus obliquus sp-21, which is 28.7 and 29.8% of the cell dry weight, respectively. The analysis of the fatty acid composition of the cells showed that the largest mass fraction of saturated and monounsaturated fatty acids was found in strain Scеnеdеsmus obliquus sp-21 - 61.9%. In the result, Scеnеdеsmus obliquus sp-21 strain isolated from thermal sources was selected as a promising candidate for biodiesel production. Highlights • 16 species of microalgae were identified in hot springs, Kazakhstan. • Scеnеdеsmus obliquus sp-21 accumulated 29.8% of lipids in the biomass. • Fatty acid composition of total lipids was suitable for biodiesel production. • Scеnеdеsmus obliquus sp-21 is promising candidate for biodiesel production. [ABSTRACT FROM AUTHOR]