Biosynthesis of polyhydroxybutyrate from methane and carbon dioxide using type II methanotrophs
Diep Ngoc Pham, Dung Hoang Anh, Eun Yeol Lee
Abstract
Methane (CH 4 ) and carbon dioxide (CO 2 ) are the dominant greenhouse gases (GHGs) that are increasing at an alarming rate. Methanotrophs have emerged as potential CH 4 and CO 2 biorefineries. This study demonstrated the synchronous incorporation of CH 4 and CO 2 into polyhydroxybutyrate (PHB) for the first time using 13 C-labeling experiments in methanotrophs. By supplying substantial amounts of CO 2 , PHB content was enhanced in all investigated type II methanotrophic strains by 140 %, 146 %, and 162 %. The highest content of PHB from CH 4 and CO 2 in flask-scale cultivation reached 38 % dry cell weight in Methylocystis sp. MJC1, in which carbon percentage in PHB from CO 2 was 45 %. Flux balance analysis predicted the critical roles of crotonyl-CoA carboxylase/reductase and phosphoenolpyruvate carboxylase in CO 2 recycling. This study provided proof of the conversion of GHGs into a valuable and practical product using methanotrophic bacteria, contributing to addressing GHG emissions.