Enhancing high quality oil accumulation and carbon dioxide fixation by a mixed culture of Chlorella sp. and Saccharomyces cerevisiae

• We demonstrate a mixed culture of microalgae and yeast to enhance oil accumulation.
• Biofixation of CO2 was enhanced by using a mixed culture of microalgae and yeast.
• The optimal light intensity for cells is found different from that for oil formation, and the specific oil productivity of the mixed culture increased with light intensity.
• The biodiesel derived from a mixed culture has better oxidative stability.

Mixed culture of Chlorella sp. and Saccharomyces cerevisiae was proposed as a novel strategy for enhancing CO2 biofixation rate and oil formation as compared with the traditional monoculture of microalgae. A symbiotic relationship of the mixed culture was observed, resulting in that the improvements of cellular biomass and oil accumulation reached 128.1% and 165.2%, respectively. Influence of light intensity ranging from 1000 to 8000 lux on the cell growth and product formation of the mixed culture was significant but different; the optimal light intensity for cell growth was at 5000 lux, but for product formation was at 8000 lux. The CO2 biofixation rate of a mixed culture reached 64.76 mg/L/h, which was 195% improvement as compared to that of the monoculture of Chlorella sp. aerated with air. The biodiesel from the mixed culture would show better quality in terms of oxidative stability as compared to those from the monoculture.