Differential Expression of Acetyl-CoA Carboxylase (Accase) Gene in Chlorella Ellipsoidea under Nitrogen Replete and Deplete Condition Along with Growth, Lipid and Fatty Acid Profile

Abstract

The present study aims at exploring the role of nitrogen on growth, lipid and fatty acid content and profile and corresponding differential Acetyl-CoA carboxylase (ACCase) gene expression in Chlorella ellipsoidea in BBM media. Chlorella ellipsoidea is a single-celled oleaginous microalgae and also a nutritious food with high protein content. C. ellipsoidea is a high quality biomass for producing algal oil. The growth of C. ellipsoidea was affected by N+ condition (maximum OD: 0.1929; maximum cell density: 6820 x105 ) and N- condition (maximum OD: 0.1284; maximum cell density: 1733x105 ). The lipid productivity of C. ellipsoidea under nitrogen repletion (N+) condition was 12% on dry weight basis while under nitrogen deplete condition (N- ) it was 17% on 23rd day of harvesting. C16 and C18 fatty acids comprised major components in both N+ and N- conditions. The main components were palmitic acid (C16:0), oleic acid (C18:1), stearic acid (C18:0) and linoleic acid (C18:2) in cultures grown under N+ condition and in N-condition the main components were palmitic acid (C16:0), oleic acid (C18:1) and linoleic acid (C18:2). However, stearic acid (C18:0) showed a sharp decline in case of cultures grown under Ncondition as compared to N+ condition. Moreover, α-linolenic acid (18:3) showed a sharp increase from 20.3% to 32.6% in N+ to N- cultures. Quantitative real time PCR (qRT-PCR) analysis of ACCase gene from nitrogen repletion (N+) and nitrogen depletion (N- ) conditions showed 0.6322 fold up regulation of ACCase gene in N- cultures of C. ellipsoidea cultures as compared to N+ cultures. The growth rate was more in nitrogen repletion condition as compared to nitrogen depletion. However, the lipid percentage was more in Nitrogen depletion condition than in repletion condition. Fatty acid methyl esters (FAME) analysis showed that the main components were C16 and C18 fatty acids in cultures grown under both the conditions, which are considered suitable for biodiesel production.