Production of poly-β-hydroxybutyric acid(PHB) from Liquefied Natural Gas using an Obligatory Methanotroph Methylosinus trichosporium OB3b

Abstract

An obligatory methanotroph Methylosinus trichosporium OB3b was cultivated for the production of poly-β -hydroxybutyric acid(PHB) in shake-flask using liquefied natural gas(LNG) as the sole source of carbon and energy. The maximal specific growth rate decreased by 40% using LNG compared with that obtained with pure methane. This is attributed to the inhibition by ethane and propane presents in the LNG as impurities. For the production of PHB, two-stage culture separating the production stage from the growth stage was carried out. PHB accumulation was observed after switching nutrient-sufficient to nutrient-limited condition of non-carboneous component (NO3-, PO43-, K+, Na+, Fe2+, or Mg2+). The limitation of K+ or Mg2+ resulted in relatively high PHB content, but the highest content was obtained by nitrate limitation. The optimal pH and temperature for PHB accumulation was 7.0 and 30∘C . Under the optimal condition the maximal PHB content was about 45% after 4-day cultivation.