Induction of vitamin B12 to purify biogas slurry and upgrade biogas using co-culture of microalgae and fungi

Abstract

Different gradient concentrations of vitamin B12 (0, 10, 100, 1,000 ng L^-1 ) were used in the symbiosis system (Chlorella vulgaris-Ganoderma lucidum or Chlorella vulgaris-Pleurotus ostreatus) to assess their effect on simultaneous purification of biogas and removal of nutrients in biogas slurry using co-culture of microalgae and fungi. When B12 was added to the symbiosis system, biomass growth, intracellular carbonic anhydrase activity (CA), chlorophyll a content (CHL-a), photosynthetic characteristics of the two cultivation system, and removal efficiency of nutrients in biogas slurry and CO₂ in biogas were significantly higher than those in the control group. The optimal concentration of B12 was determined to be 100 ng L^-1 considering the removal efficiency of nutrients and CO₂ . Maximum mean chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP), and CO₂ removal efficiencies were 75.98 ± 6.26%, 78.46 ± 6.21%, 80.21 ± 6.83% and 61.08 ± 5.21% in Chlorella vulgaris-Ganoderma lucidum, respectively. This study showed the potential of microalgae and fungi symbiosis system with B12 addition for nutrient removal and biogas upgrading. PRACTITIONER POINTS: Vitamin B12 had positive effects on algal-fungal pellets growth. The optimal vitamin B12 concentration was 100 ng L^-1 . The highest CO₂ remove rate was 61.08% by G. lucidum/C. vulgaris pellets. Vitamin B12 significantly improved photosynthetic performance of pellets.

Keywords: Vitamin B12; nutrient removal; photosynthetic characteristics; upgrade biogas.