BACKGROUNDCarbon dioxide fixation by microalgae is a promising biotechnology for reduction of CO2 emissions, however, the photosynthetic process of microalgae is inhibited by excessive dissolved oxygen, especially in enclosed photobioractors. In this study, a consortia of microalgae and yeast was used to investigate the effect of yeast on biomass production, photosynthetic activity and CO2 biofixation rate in the microalgae. RESULTSThe biomass concentration and net photosynthetic activity of a co-culture of Scenedesmus obliquus and Candida tropicalis was increased by 30.3% and 61%, respectively, compared with S. obliquus alone, but no stimulation was observed in a co-culture of S. obliquus and Saccharomyces cerevisiae. The best S. obliquus/C. tropicalis seed ratio for microalgal growth was 3:1, showing the highest concentration of biomass and net photosynthetic activity. Degradation of the extracellular polymeric substances provided nutrition for the yeast and created a suitable microenvironment for the microalgae. Moreover, the co-culture of S. obliquus and C. tropicalis enhanced the lipid content and productivity compared with the microalgae alone. CONCLUSIONThe consortia of S. obliquus and C. tropicalis enhanced the biomass and lipid production of microalgae. It was a suitable solution to the problem of excessive dissolved oxygen in an enclosed photobioreactor. (c) 2015 Society of Chemical Industry