Enhanced biomass and lipid production by co-cultivation of Chlorella vulgaris with Mesorhizobium sangaii under nitrogen limitation

Microalgal lipids have been considered as one of the most promising feedstocks for biodiesel production. In order to solve the contradiction of algae growth and lipid accumulation, Chlorella vulgaris was co-cultured with Mesorhizobium sangaii under nitrogen deficiency conditions. The biomass and lipid production of C. vulgaris-bacteria co-culture with initial ratio of algae/bacteria = 40:1 were significantly improved compared with the pure algae culture. The maximum biomass, lipid content and productivity of algae in the co-cultures at 40:1 ratio were 1.89 mg L-1, 51.2%, and 96.77 mg L-1 day(-1), respectively, which were 1.5, 2.2, and 3.3 times higher than those of the pure algae culture. Furthermore, the proportion of unsaturated fatty acids and C18:1 fatty acid of the consortium system was also significantly increased. Our study clearly suggests that co-cultivation of algae-bacteria can effectively contribute to the quality and quantity of microalgal bio-oil and shows promising applications for production of algal biomass and biodiesel. Graphical abstrac