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

Abstract

We aimed to explore a new Methylobacterium isolate to produce polyhydroxybutyrate (PHB) by using methanol as a sole carbon resource and improve PHB production. 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 0·6gl-1 after 3-day culture and 0·3gl-1 PHB was produced after 5-day methanol-inducing stage. The RSM growth medium was optimized as 15gl-1 glycerol, 10gl-1 beef extract and 0·65gl-1 MgSO4 ·7H2 O. The RSM methanol-inducing medium was optimized as 0·65gl-1 MgSO4 (metal ions), 20mmoll-1 PBS pH 6·5 and final 2% methanol (v/v). The biomass and PHB production reached 1·0 and 0·55gl-1 after 3-day culture, respectively. The PHB yield increased by about 80% when compared with before optimization. The optimization of a two-stage fermentation process improved PHB production from methanol by using Methylobacterium sp. 1805. 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.