Growth of Methylosinus trichosporium OB3b on methane and poly-β-hydroxybutyrate biosynthesis

Optimal conditions for batch cultivation of the obligate methanotroph Methylosinus trichosporium OB3b on methane without superatmospheric pressure were chosen. The yield of absolutely dry biomass after 120 h of growth reached 20 g/l. This biomass contained 30% poly-beta-hydroxybutyrate (PHB) with molecular weight 300 kDa. The growth process included the stages of biomass growth and PHB biosynthesis. The latter stage occurred under nitrogen-deficiency conditions. It was accompanied by an increase in the activity of PHB biosynthesis enzymes (beta-ketothiolase, acetoacetyl-CoA reductase, and PHB synthase) and the main NAD(P)H producer, methylenetetrahydromethanopterin dehydrogenase. The activity of PHB depolymerase increased insignificantly.