Due to their lipid accumulation potential, microalgae are widely studied in terms of their use in the production of biodiesel. The present study was focused on determination of changes in the biomass production, biochemical composition, accumulation and distribution of fatty acids in neutral lipids, glycolipids, phospholipids and biodiesel properties of soil microalga Eustigmatos calaminaris in response to various levels of nitrogen stress and indole-3-acetic acid supplementation. The highest growth rate, the highest lipid content and daily lipid productivity were noted at the nitrogen limitation up to 25% with IAA supplementation. The increase in NL was associated with nutrient stress. An increase in the level of GL and PL were recorded upon the reduction of the nitrogen content (25% N) and the addition of IAA. The gas chromatography/mass spectrometry analysis demonstrated that C16:0, C16:1, and C18:1 were the main fatty acids in E. calaminaris lipids. As shown by the lipidomic analysis, the IAA supplementation in the nitrogen limitation variants enhanced the content of TAGs in C18:1 and monounsaturated fatty acids. The current findings indicated a potential strategy to improve the fatty acid profile in neutral lipids and high potential of E. calaminaris for biodiesel applications.
In the present study, the potential of lead and cadmium removal by the extracellular polymeric substances (EPS) produced from Parachlorella kessleri and Chlorella vulgaris were investigated. Carbohydrates were the dominant components of EPS from both analyzed species. The contents of reducing sugars, uronic acids, and amino acids were higher in EPS synthesized by C. vulgaris than in EPS from P. kessleri. The analysis of the monosaccharide composition showed the presence of rhamnose, mannose and galactose in the EPS obtained from both species. The ICP-OES (inductively coupled plasma optical emission spectrometry) analyses demonstrated that C. vulgaris EPS showed higher sorption capacity in comparison to P. kessleri EPS. The sorption capacity of C. vulgaris EPS increased with the increase in the amount of metal ions. P. kessleri EPS had a maximum sorption capacity in the presence of 100 mg/L of metal ions. The FTIR analysis demonstrated that the carboxyl, hydroxyl, and carbonyl groups of EPS play a key role in the interactions with metal ions. The present study showed C. vulgaris EPS can be used as a biosorbent in bioremediation processes due to its biochemical composition, the presence of significant amounts of negatively charged uronic acids, and higher sorption capacity.
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