Methanotrophic and heterotrophic co-cultures for the Polyhydroxybutyrate production by co-utilizing C1 and C3 gaseous substrates

Abstract

Polyhydroxybutyrate (PHB) production using methanotrophs offers an economical solution to counter increasing environmental pollution. However, the substrate specificity of methanotrophs limits their ability to use multiple gases for chemical production. In this study, a synthetic heterotrophic and methanotrophic co-culture system was developed to co-utilize methane and propane for PHB production. First, a heterologous pathway was constructed in Escherichia coli BL21 (DE3) to produce PHB from acetone. Later, Methylocystis sp. OK1 produced acetone from propane; however, its PHB content decreased when methane and propane were co-utilized. Subsequently, the recombinant E. coli strain was co-cultured with Methylocystis sp. OK1 in the presence of methane and propane, which enhanced the PHB yield by 35%, 65%, and 100% with propane concentrations of 7% (v/v), 13% (v/v), and 20% (v/v), respectively, compared to the mono-cultures of Methylocystis sp. OK1. The results demonstrated PHB production in heterotrophic and methanotrophic co-cultures through co-utilization of methane and propane.

Keywords: Acetone carboxylase; Bioplastic; Methane; Methylocystis sp. OK1; Propane.