Efficient resource recycling from liquid digestate by microalgae-yeast mixed culture and the assessment of key gene transcription related to nitrogen assimilation in microalgae

To determine the feasibility of microalgae-yeast mixed culture using the liquid digestate of dairy wastewater (LDDW) for biofuels and single cell protein (SCP) production, the cell growth, nutrient removal and outputs evaluation of the mono and mixed culture of Chlorella vulgaris and Yarrowia lipolytica in LDDW were investigated by adding glycerol as carbon source. The results showed that the mixed culture could enhance the biological utilization efficiency of nitrogen and phosphorus, and obtain higher yield of biomass (1.62 g/L), lipid (0.31 g/L), protein (0.51 g/L), and higher heating value (34.06 KJ/L). Compared with the mono culture of C. vulgaris, a decline of the transcription level in nitrate reductase and glutamine synthetase II genes in C. vulgaris was observed in the mixed culture when ammonia was sufficient. The results suggest the possibility of using the mixed culture for the efficient treatment of LDDW and resources recycling.