Effects of l-amino acids as organic nitrogen source on the growth rate, biochemical composition and polyphenol content of Spirulina platensis

Nitrogen plays on important role in enhancing the biochemical composition during photosynthesis. The form of nitrogen source either organic or inorganic further has an impact on the growth and biochemical composition of microalgae. The present work focuses on the influence of various l-amino acids on the growth rate, biochemical composition and polyphenol content of Spirulina platensis. Addition of 0.1 g L−1 of l-Arginine, l-Asparagine and l-Glutamine exerted the biomass productivity of 175.8 ± 0.005, 153.0 ± 0.001 and 144.2 ± 0.003 mg L−1 day−1 respectively while it was 114.0 ± 0.003 mg L−1 day−1 for conventional medium. The yield of protein could be increased by 29% under 0.1 g L−1 of l-Arginine. Addition of 0.05 g L−1 of l-Asparagine increased the carbohydrate and lipid content by 260% and 242% compared with inorganic nitrogen. The in-vitro digestibility of the feed protein is in the order of l-Arginine > l-Asparagine = Nitrate > l-Glutamine. The polyphenol content was 5.0 ± 0.5 4.0 ± 0.2 and 3.2 ± 0.4 mg g−1 for l-Asparagine, l-Glutamine and l-Arginine respectively which is higher than that of inorganic nitrogen (2.4 ± 0.2 mg g−1). The results indicate that the l-amino acids could be utilized by the S. platensis to improve the overall biochemical composition and the resulting biomass may have potential application for food and biofuel production.