Transcriptome analysis reveals metabolic regulation mechanism of microalga Chlorella pyrenoidosa in response to the mixed culture with yeast Yarrowia lipolytica

The mixed culture of microalgae and yeast has been confirmed to enhance many bioprocesses including waste degradation, remediation, and biomass generation for lipid production. Our latest study showed that besides the higher yield of biomass and lipid, the mixed culture of Chlorella pyrenoidosa and Yarrowia lipolytica can achieve the higher yields of carbohydrates, protein, and higher heating value. The strengthening mechanism of the mixed culture of microalgae and yeast mostly focused on nutritional complementarity and the culture conditions in previous works. In this work, de novo transcriptome profiling and central metabolic pathway analysis of C. pyrenoidosa cells in mono microalgae culture and mixed culture were performed. The differential transcriptome analysis revealed that most biological processes of C. pyrenoidosa, such as TCA cycle, glycolysis/gluconeogenesis pathway, pentose phosphate pathway, and nitrate assimilation, were enhanced by the mixed culture with yeast at 24 h. Meanwhile, the CO assimilation of C. pyrenoidosa was inhibited. Deep analysis of carbon metabolism, nitrogen metabolism, and photosynthesis well illustrates the intrinsic mechanism of physiological and biochemical differences occurring in the mono microalgae culture and the mixed culture. This study unraveled metabolic regulation molecular mechanism of C. pyrenoidosa in response to the mixed culture with Y. lipolytica, and strengthens the understanding of the synergistic effect between microalgae and yeast in the mixed culture.