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

Abstract

Under nutrient -limited conditions, Type II obligate methanotrophs accumulate intracellular poly(3hydroxybutyrate) (P3HB) granules using C1 compounds such as methane or methanol. In this study, Methylocystis parvus OBBP, under similar conditions, utilizes ethane as its sole carbon source, achieving 35 +/- 4 wt% P3HB. 13C NMR confirms 13C incorporation from [13C2]ethane. Quantitative results indicate that methane -fed cultures reach 48 +/- 5 wt% P3HB with a total suspended solids (TSS) concentration of 1820 +/- 200 mg/L. Ethane -fed cultures yield slightly lower P3HB (35 +/- 4 wt%) and reduced TSS (1440 +/- 160 mg/L). Patterns of ethane and oxygen consumption suggest the presence of inhibitory substances. When valerate is introduced with ethane, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) synthesis is facilitated. With valerate, ethane facilitates 12.9 +/- 2.6 % PHBV synthesis, with a 25 +/- 0.01 % 3HV mole fraction. These findings highlight M. parvus OBBP's efficient ethane utilization for high -yield P3HB production, holding promise for industrial biopolymer synthesis.