Maximizing Biomass and Lipid Production in Heterotrophic Culture of Chlorella vulgaris: Techno-Economic Assessment

Abstract

Nowadays, chlorophycean microalgae have attained a broad-spectrum attention as a potential candidate for biomass and bioenergy production. Despite their appreciated benefits, one of major problems is their low biomass and lipid productivity. Here we investigated the heterotrophic culture in shake flasks and stirred tank bioreactor to improve the lipid and biomass production in a naturally isolated strain of Chlorella vulgaris. A naturally isolated C. vulgaris strain was cultivated in BG-11 medium in shake flask and bioreactor. Its biochemical composition and growth kinetic parameters were investigated. The biomass productivity was improved (3.68 fold) under heterotrophic culture compared to basal autotrophic culture condition in shake flask experiment. The total lipid content increased to 44% of total Dry Cell Weight (DCW) during heterotrophic growth after 21 days. Moreover, a great Fatty Acid Methyl Esters (FAME) yield was observed under heterotrophic cultivation. Total biomass and lipid content of microalgae in bioreactor experiment increased to 4.95 and 2.18 g L-1 respectively, during 5 days of the experiment compared to its basic autotrophic culture. The techno-economic aspects of exploiting C. vulgaris as a biodiesel feedstock werealso evaluated. The results imply that heterotrophic cultivation could compensate the low biomass productivity in microalgae for green energy production. Ever growing rates of established patents on application of various genetic and bioengineering-based methods have made it possible to achieve higher lipid contents with reduced total costs for microalgal biodiesel production as well.