Methane Based Continuous Culture of Methylosinus trichosporium for Production of Poly-3-hydroxybutyrate Using Membrane Recycle System

Poly-3-hydroxybutyrate (PHB) is a bio-based and biodegradable polymer produced by microbial fermentation from wide variety of feedstocks. Methanotrophic organism Methylosinus trichosporium has been reported for the production of PHB using alternate feedstock like methane which is economical and abundantly available. PHB was produced from methane by cultivating M. trichosporium in a bioreactor with continuous cell recycle system. Different gas sparging strategies were evaluated for impact on cell biomass and PHB production. The fermentation was conducted in different modes including batch and continuous culture with and without membrane recycle. Using membrane based recycle system the biomass increased from 1.5 to maximum of 7.31 g DCW/L in 27 days. Although PHB content was comparable in both batch mode and membrane based recycle system, a 4.9 fold increase in biomass production enhanced the PHB titer by 6.1 fold as compared to batch culture. Continuous cell recycle processes provide an opportunity to increase the competitiveness of gas fermentation based processes for methanotrophs based PHB production.