MICROALGAE AS POTENTIAL PROTEIN SOURCES: EVIDENCE FROM PROTEIN EXTRACTION AND AMINO ACID PROFILING OF Chlorella vulgaris AND Scenedesmus SP.

The high protein contents in green microalgae can be used for the generation of bioactive peptides for feed, food, and health. Many methods are available for the extraction of microalgal protein but they are not easily scalable due to the requirement of special techniques and instruments. In the present work, the nitrogenous component of green microalgae Chlorella vulgaris and native species Scenedesmus sp. were quantified by the Lowry method and their amino acid composition was analyzed and compared. Proteins extraction was done by milling algal biomass, solubilization at various concentrations of NaOH, and precipitation at acidic pH. In results, both Scenedesmus sp. and C. vulgaris showed the maximum specific growth rate i.e. 0.653 and 0.589 g L-1 d(-1), respectively in Bold's Basal Medium. Grinding biomass and then alkaline (1N) treatment at 100 degrees C for 10 min resulted in the maximum protein extraction from both species. Under optimum conditions, an increase of 19 and 18% in protein contents of Chlorella vulgaris and Scenedesmus sp., respectively compared to control treatment was noted. Regarding amino acid profiling, glutamic and aspartic acids were found in the highest concentrations in Scenedesmus sp. (2.9 and 2.5%) and C. vulgaris (3.2 and 2.8%), respectively. Six amino acids (alanine, aspartic acid, glutamic acid, leucine, lysine, and glycine) were responsible for 50% or more of the total detected amino acid contents in both microalgal species. In conclusion, the consolidating activity of freeze-drying and milling the dry biomass along with alkaline extraction significantly boosted the protein yield.