New approach for raw biogas: Production of single cell protein by sulfide-tolerant methane-oxidizing bacteria consortia

• Sulfide-tolerant Methane-oxidizing bacteria and consortia were obtained. • Single cell protein (SCP) production from raw biogas was practicable. • Compared to pure culture, consortia showed significant production advantages. • Na 2 S influenced the amino acid composition to some extent. Methane-oxidizing bacteria (MOB) have tremendous potential in utilizing biogas to produce single cell protein (SCP). However, the raw biogas contains H 2 S, which could affect the growth of MOB. This study aimed to screen sulfide-tolerant MOB or sulfide-tolerant MOB consortia to produce single cell protein from raw biogas. Firstly, four sulfide-tolerant MOB consortia were enriched from paddy soil by addition of different concentrations of Na 2 S (the highest equivalent 2973 ppmv H 2 S). Microbial community analysis revealed that the highest abundance in different groups was dominated by the same species of MOB- Methylocystis parvus OBBP. Experiments used the pure culture of M. parvus OBBP indicated that this strain had a certain tolerance to Na 2 S. However, MOB consortia performed better for SCP production: the maximum biomass of the MOB consortia was 1.516 (±0.187) g/L, with protein content of 56.10 % (±10.99 %), while the maximum biomass of the pure culture was only 0.818 (±0.106) g/L, with protein content of 37.12 % (±7.40 %). Network analysis displayed that Ciceribacter , Pseudoxanthomonas , Edaphobaculum , Prosthecobacter, Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium showed positive correlation with M. parvus OBBP, indicating they might be the most important partners of M. parvus OBBP. This study provides a promising way for the direct utilization of raw biogas to produce SCP, which also provides references for artificially construction of MOB consortia.