Co-cultivation of methane oxidizing bacteria and photosynthetic bacteria for single cell protein production

Single cell protein (SCP) is widely used in food and feed due to its high protein content, rich essential amino acids, low fat content, and presence of various trace elements. It can serve as a dietary supplement in animal diets or as a substitute for certain proteins. Methane-oxidizing bacteria (MOB), which utilize methane as their sole carbon and energy source and are not limited by factors such as land or light, are a significant asset for SCP production. Their co-culture system with photosynthetic bacteria (PSB) can further enhance SCP production efficiency. By comparing monoculture and co-culture data, it was confirmed that a synergistic interaction based on intracellular substance exchange exists between two mixed microorganisms: adding intracellular substances from MOB increased the maximum OD₆₀₀ of PSB by 19% and cell dry weight by 10%, while adding intracellular substances from PSB increased the OD₆₀₀ of MOB by 32% and cell dry weight by 2.06 times. Under nitrogen-limited conditions, the co-culture system achieved 2.26 times higher OD₆₀₀ and 2.6 times greater cell dry weight compared to monoculture, demonstrating that the nitrogen-fixing activity of PSB effectively supplemented nitrogen sources. In normal nitrogen-supplied medium, the co-culture increased methane consumption by 13% (0.1252 g vs. 0.1108 g), SCP yield by 8% (0.349 vs. 0.323 g DCW/g CH₄), and cell dry weight by 21%. 16S rRNA analysis revealed that MOB dominated the co-culture system (46.25%), with photosynthetic cyanobacteria as a secondary component (10.9%), validating the ecological structure of this synergistic system. The research outcomes provide a novel and efficient co-culture model for optimizing industrial SCP production.