Effects of exogenous vitamin B12 on nutrient removal and protein expression of algal-bacterial consortium

Chlorella vulgaris and Bacillus licheniformis consortium was added to synthetic wastewater with exogenous vitamin B 12 . In the presence of 100 ng/L vitamin B 12 , removal efficiencies of TN, NH 3 -N, PO 4 3— P, and COD were 80.1%, 76.8%, 87.9%, and 76.7%, respectively. The functional groups on the cell surface of the consortium, including -NH, -CH 3 , C=O, C=C, and P-O-C, increased with 100 ng/L vitamin B 12 . These functional groups improved the biological adsorption of the consortium; however, higher concentrations of vitamin B 12 resulted in an occlusion of the functional groups. Furthermore, there were 5 significantly enriched protein pathways, namely carbon fixation in photosynthetic organisms; amino acid metabolic pathways; the pathway of one carbon pool by folate; nitrogen metabolism; and photosynthesis. Most proteins in these pathways were upregulated, which enhanced carbon fixation and photosynthesis in the algal cells. Simultaneously, B 12 promoted significant upregulation of proteins associated with the quorum-sensing pathway, which promoted the interaction between algae and bacteria.