Poly-3-hydroxybutyrate production from methanol by Methylosinus trichosporium IMV3011 in the non-sterilized fed-batch fermentation

Abstract

The methanotrophic bacteria have promising applications in the production of a biopolymer, poly-3-hydroxybutyrate (PHB). The fed-batch fermentation strategies were studied for PHB accumulation by methanol-grown Methylosinus trichosporium IMV3011 under the non-sterilized conditions. The biomass of 2.91 g dry wt/L and PHB accumulation of 47.6% (w/w) were reached in the fed-batch fermentation. In order to increase PHB content, some organic acids were added into the culture as inhibitors of tricarboxylic acid cycle (TCA). It was found that the malic acid should be optimum for PHB accumulation. The biomass and PHB yield would increase to 3.32 g dry wt/L and 58.5% (w/w), respectively by adding 0.2 g/L malic acid. Other key intermediates in the metabolism such as citric acid, succinic acid and acetyl-CoA, also influenced the cell growth and PHB accumulation to a certain extent. The PHB produced in the fermentation process was of steady quality with molecular weights up to 1.7 × 106 Da. Key words: Biosynthesis, poly-3-hydroxybutyrate, methanotrophic bacteria, methanol, fed-batch fermentation.