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 0·6 g l −1 after 3‐day culture and 0·3 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 0·65 g l −1 MgSO 4 ·7H 2 O. The RSM methanol‐inducing medium was optimized as 0·65 g l −1 MgSO 4 (metal ions), 20 mmol l −1 PBS pH 6·5 and final 2% methanol (v/v). The biomass and PHB production reached 1·0 and 0·55 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.