Single cell protein production potential of enriched microbial populations from rice paddy soils and roots: Insights into protein yield enhancement by Methylophilaceae.

This study aimed to determine key factors for enriching methylotrophic populations for single-cell protein (SCP) production and to determine the predominant active methylotrophs. Microbial populations from rice paddy soils and roots, hotspots for CH4 oxidation, underwent serial incubation by feeding CH4 and O2. The protein content was primarily influenced by the incubation stage, with a lesser effect from the rice plant roots as an inoculum source, reaching a maximum of 20 % in biomass dominated by Methylomonadaceae and Methylophilaceae. While Methylomonadaceae as CH4 oxidizers exhibited lower abundance but high transcription activity, Methylophilaceae as methanol oxidizers were more abundant and strongly correlated with protein content (Pearson's coefficient >0.8, p < 0.05). Enhancing Methylophilaceae in the mixed cultures may improve SCP yields via interactions with Methylomondaceae, likely mediated by methanol. The cooperative relation plausibly offers a promising strategy for sustainable CH4-based SCP production.