Heterotrophic/mixotrophic cultivation of oleaginous Chlorella vulgaris on industrial co-products

Among many challenges faced in the commercial cultivation of microalgae, low-cost water and nutrients availability is crucial. Our study aimed at testing and optimizing two agro-industrial co-products, dry-grind ethanol thin stillage (TS) and soy whey (SW), as nutrient feedstock for mixotrophic/heterotrophic microalgal cultivation. Heterotrophic growth of Chlorella vulgaris was first optimized in a Bioscreen turbidimeter and 250 mL Erlenmeyer flasks, then scaled up to a 6-L stirred bioreactor. Intracellular oil was extracted from dried microalgal biomass by ultrasonication and solvent extraction treatments for yield comparison, and fatty acid (FA) profile. Biomass yields (dry basis) from TS, SW and modified basal medium (MBM) after 4 days of incubation at mixotrophic conditions in the bioreactor were 9.8, 6.3 and 8.0 g.L-1 with oil content at 43, 11, and 27% (w/w) respectively. FA profile of oil samples was found to vary and depend on growth media characteristics. C vulgaris when grown on TS and MBM produced oil richer in linoleic and linolenic acids, respectively. This research highlights the potential of two agro-industrial co-products as microalgal growth media with consequent production of high-value microalgal oil and biomass. (C) 2012 Elsevier B.V. All rights reserved.