Investigating the modulation of metabolites under high light in mixotrophic alga Asteracys sp. using a metabolomic approach

Metabolomic fluctuations in microalgal cells under mixotrophic growth regimes are scarcely understood. Our study explores these changes in an oleaginous microalga, Asteracys sp. when grown mixotrophically under high irradiances. Biomass production under autotrophic and mixotrophic regimes were studied at two light intensities (LL; 100 mu mol photonsm(-2) s(-1) and HL; 900 mu mol photonsm(-2) s(-1)) for Asteracys sp. Studies on supplementation of external carbon such as glucose (mixotrophic mode) under different light intensities has not been demonstrated in context with enhanced biomass production. In the present study, we have provided external source of carbon as glucose in LL and HL regimes and observed a marked influence of glucose assimilation on the overall machinery of the cell. Our qualitative metabolomics reveals a stress-like phenomenon in Asteracys sp. under HL with enhanced biomass. In overview, our data analysis highlights few metabolites such as trehalose, proline and a-tocopherol that showed significant changes in response to light as well as in growth regime. Our analysis predicts an interrelation cross talk between maltose and sucrose pathways within cells owing to possible alteration in starch degradation under the influence of light. However, mixotrophy with additional carbon supplementation in presence of light did not alter or enhance lipid biosynthesis. In conclusion, our hypothesis indicates modulation of metabolites in presence of glucose under high light would rather facilitate rearrangement in metabolic pathways for enhanced biomass production.