Individual and combined supplementation of carbon sources for growth augmentation and enrichment of lipids in the green microalga Tetradesmus obliquus

Abstract

Microalgae with high lipid productivity offer great promise as a potential source of biodiesel, an alternative to fossil diesel. Since a target of both high biomass yield and lipid content is difficult to attain with the classical photoautotrophic mode of nutrition, mixotrophy has evolved as a preferred mode for enhancement of growth in microalgae. In the present study, this strategy was explored extensively with six different exogenous carbon sources in eight different concentrations to investigate the effect of these carbon sources on the biomass and lipid production potential of the green alga Tetradesmus obliquus (SAG 276-3a). To further augment the effect of mixotrophy on the growth and lipid accumulation of the test microalga, selected carbon sources with their specific concentrations showing enhancement in both biomass yield and lipid accumulation in the first phase of the experiment were interacted with each other. Significant rise in biomass yield by twofold was seen in the case of 0.16% citrate + 0.08% bicarbonate interaction, whereas for lipid accumulation, maximum rise in lipid content (% dry cell wt.) by 2.3-fold and lipid yield (g L-1) by 4.5-fold was observed in the case of 0.16% acetate + 0.16% citrate-supplemented cultures. The biodiesel samples as analyzed using GC–MS were predominated with saturated and monounsaturated fatty acid methyl esters. Fuel property analysis of the biodiesel samples found them to be well suited to the Indian, American (ASTM), and European (EN) biodiesel standards.