Two-stage fermentation optimization for poly-3-hydroxybutyrate production from methanol by a new Methylobacterium isolate from oil fields

Aims We aimed to explore a new Methylobacterium isolate to produce polyhydroxybutyrate (PHB) by using methanol as a sole carbon resource and improve PHB production. Methods and Results A new PHB-producing isolate (Methylobacterium sp. 1805) was obtained from oil fields by using methanol as a sole carbon source. The fermentation situation of PHB production was further optimized by using Box-Behnken response surface methodology (RSM). Before optimization, the cell biomass was 0 center dot 6 g l(-1) after 3-day culture and 0 center dot 3 g l(-1) PHB was produced after 5-day methanol-inducing stage. The RSM growth medium was optimized as 15 g l(-1) glycerol, 10 g l(-1) beef extract and 0 center dot 65 g l(-1) MgSO4 center dot 7H(2)O. The RSM methanol-inducing medium was optimized as 0 center dot 65 g l(-1) MgSO4 (metal ions), 20 mmol l(-1) PBS pH 6 center dot 5 and final 2% methanol (v/v). The biomass and PHB production reached 1 center dot 0 and 0 center dot 55 g l(-1) after 3-day culture, respectively. The PHB yield increased by about 80% when compared with before optimization. Conclusions The optimization of a two-stage fermentation process improved PHB production from methanol by using Methylobacterium sp. 1805. Significance and Impact of the Study A new Methylobacterium isolate was isolated and produced high-level PHB by using methanol as a sole carbon resource. The bacteria will provide a potential tool for C1 resource in producing PHB.