Co-Fermentation of Chlorella vulgaris with Oleaginous Yeast in Starch Processing Effluent as a Carbon-Reducing Strategy for Wastewater Treatment and Biofuel Feedstock Production

Low biomass yield and nutrient removal efficiency are problems challenging the employment of microorganisms for wastewater remediation. Starch processing effluent (SPE) was used as a fermentation substrate to co-culture Chlorella vulgaris and Rhodotorula glutinis for biofuel feedstock production. Co-culture options were compared, and the optimal conditions were identified. The result shows that microalgae and yeast should be inoculated simultaneously at the beginning of SPE-based fermentation to achieve high biomass yield and the optimal inoculation ratio, light intensity, and temperature should be 2:1, 150 mu mol/m(2)/s, and 25 degrees C, respectively. Under the optimal conditions, the lipid yield of microorganisms was 1.81 g/L and the carbon-conversion ratio reached 82.53% while lipid yield and the carbon-conversion ratio in a monoculture fell in the range of 0.79-0.81 g/L and 55.93-62.61%, respectively. Therefore, compared to the monoculture model, the co-fermentation of Chlorella vulgaris and Rhodotorula glutinis in starch processing effluent could convert nutrients to single-cell oil in a more efficient way. It should be noted that with the reduced concentration of residual organic carbon in effluent and the increased carbon-conversion ratio, co-fermentation of microalgae and yeast can be regarded as a promising and applicable strategy for starch processing effluent remediation and low-cost biofuel feedstock production.

Automated summary

Simultaneous inoculation of microalgae and yeast is the optimal strategy for utilizing starch processing effluent for biofuel feedstock production. Under the optimal conditions, the lipid yield and carbon-conversion ratio of the co-fermentation reached 1.81 g/L and 82.53%, respectively, which were higher than those of the monoculture model. Co-fermentation of microalgae and yeast in starch processing effluent is a promising and applicable strategy for wastewater remediation and low-cost biofuel feedstock production.