Production of lipids biosynthesis from Tetradesmus nygaardii microalgae as a feedstock for biodiesel production

• Tetradesmus nygaardii MT858750 was screened for higher biomass and lipids accumulation. • Nitrogen concentration and pH affected the output responses significantly. • Tetradesmus nygaardii produces high content of MUFA and PUFA that results in high quality biodiesel. The research and innovative strategies for large scale production and commercialization of algae based biodiesel still presents a need for analysis based on sustainability and quality check. In this study, the three key growth factors (nitrogen concentration, temperature and pH) were manipulated using the Box-Behnken design of the experiment, with the aim to get high lipids and biomass production for Tetradesmus nygaardii. Screening of experimental treatments revealed interactive effects of nitrogen concentration and pH manipulation, as strongly significant towards high lipids accumulation and lower biomass losses. Biomass production increased (543 mg/L) with high nitrogen, temperature and alkaline pH in the medium, while the lipids showed highest values as 272 mg/L and 60% in terms of production and lipid content with lower nitrogen, low temperature and neutral pH in medium. FTIR analysis revealed metabolic shift of protein and carbohydrate synthesis towards lipid accumulation in optimized biomass. Fatty acid methyl ester analysis revealed higher content of MUFA (53.3%) and PUFA (35%) with major contributors of C16-C18 carbon chain length fatty acids in optimized biomass. Biodiesel specifications (Density, Flash point, Cetane number, Saponification value, Acid Value, Cloud point and CFPP) met the requirements of EN14214 and ASTMD6751 biodiesel standards. The results of this study indicates that the biomass and lipid production of Tetradesmus nygaardii could highly be improved by manipulating nitrogen concentration and pH in combination. In this work, the most promising conditions for biomass and lipid production were identified and could be implemented for sustainable and quality biodiesel production.