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Ethane-dependent synthesis of polyhydroxyalkanoates by the obligate methanotroph Methylocystis parvus OBBP

Under conditions of nutrient-limited growth, Type II obligate methanotrophs oxidize C1 compounds, such as methane or methanol and accumulate intracellular granules of poly(3-hydroxybutyrate) (P3HB). Here, we report that, under same nutrient-limited conditions, the Type II obligate methanotroph Methylocystis parvus OBBP can use ethane as its sole carbon and energy source for synthesis P3HB granules, accumulating up to 35 ± 4 wt% P3HB. 13C-NMR spectra of the P3HB confirmed incorporation of 13C from [13C2]ethane. Moreover, when valerate was added as a co-substrate with ethane, oxidation of the ethane supported synthesis of the copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). IMPORTANCE The presence of ethane in natural gas is often considered undesirable for methanotroph-based biotechnology due to the C1 specialization of obligate methanotrophs and concerns about inhibitory byproducts arising from methane monooxygenase-mediated cometabolism of ethane. This work establishes that co-oxidation of ethane and further metabolism in the absence of methane can support synthesis of the valuable polyhydroxyalkanoate bioplastics P3HB and PHBV.