Photoheterotrophic growth of Chlorella vulgaris ESP6 on organic acids from dark hydrogen fermentation effluents

In this work, Chlorella vulgaris ESP6 was used to assimilate the soluble metabolites in the hydrogen fermentation broth of Clostridium butyricum CGS5 to obtain valuable microalgae biomass. The results show that C. vulgaris ESP6 could grow on the 4-fold diluted dark fermentation broth. Acetate was efficiently utilized during the growth of C. vulgaris ESP6, whereas the microalgae growth was inhibited by lactate, butyrate, and HCO 3 - when their concentrations were higher than 0.5, 0.1, and 2.72 g/L, respectively. C. vulgaris ESP6 could completely consume butyrate (the most abundant dark fermentation metabolite) when it was grown on Tris–Acetate–Phosphate medium under a food to microorganism (F/M) ratio of 1.11.