Bioplastic production potential, growth optimization, and biokinetics of methane-oxidizing bacterium Methylosinus sp....

Reducing methane (CH₄) emissions is crucial for mitigating climate change. Methane-oxidizing bacteria (MOB) convert CH₄ into biomass and valuable bioproducts, offering a promising mitigation strategy and a novel biorefinery approach. In this study, Methylosinus sp. strain C49 (MC49), a novel MOB isolated from a CH₄-rich rice paddy field, was characterized, focusing on CH₄ oxidation and polyhydroxyalkanoate (PHA) biosynthesis. MC49 grew optimally at pH 6.8 and 25 °C with 25 % CH₄ and 75 % air, classifying it as a neutrophilic, mesophilic methanotroph. Biokinetic analysis showed cell-specific maximum CH₄ oxidation rate of 8.08 × 10^-14 mg-CH₄/cell/h. Under feast-famine conditions, 94.5 % ± 4.1 % of cells accumulated PHA, reaching 22.4 wt% compared with 14.3 wt% under regular incubation. These findings highlight the dual potential of MC49 in mitigating CH₄ emissions and producing biodegradable plastics-advancing environmental biotechnology at the nexus of climate action and sustainable materials.