Methylocystis suflitae as a promising industrial workhorse for methane-based polyhydroxyalkanoate production

Growing interest in the abatement of greenhouse gases has spurred a surge in research within the field of methanotrophy in recent decades. Certain methanotrophic organisms exhibit the unique ability for the production of biodegradable polymers known as polyhydroxyalkanoates (PHAs) using methane as their solitary carbon source. In this study, we harnessed the capability of Methylocystis suflitae, a Type II methanotroph, for the production of PHA from methane. The genome analysis unveiled the presence of four paralogs of PHA synthase gene in Methylocystis suflitae. Subsequently, we elucidated the catalytic sites of each PHA synthase using protein modeling and molecular docking. Both hydroxybutyrate and hydroxydodecanoate demonstrated the highest docking energies among all the tested substrates, recording at − 7.5, and − 7.8 kcal/mol, respectively. The capability of Methylocystis suflitae to synthesize polyhydroxybutyrate (PHB) was evaluated by analyzing the FTIR spectrum, revealing the characteristic carbonyl (C = O) peak at 1723 cm⁻¹. The study included the optimization of the substrate-to-electron acceptor ratio to optimize PHA productivity. Notably, the organism exhibited a productivity value of 11.90 ± 1.34 mg PHA/L/hr. This higher productivity holds significant promise for industrial PHA production, particularly in scenarios where achieving sufficiently high dissolved methane concentrations in industrial fermenters is inherently challenging, potentially enabling more efficient PHA production. Additionally, we determined the melting temperature for PHB produced by Methylocystis suflitae which closely aligns with the standards of commercial-grade PHB, at around 188 °C.