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.
(© 2019 The Society for Applied Microbiology.)