Methane fermentation to methanol (biological gas-to-liquid process) using Methylotuvimicrobium buryatense 5GB1C

Abstract

Methanol is a potential alternate liquid transportation fuel for blending with gasoline. Biochemical conversion of methane to methanol is a green process for methanol production. This paper reports biochemical methanol production using type I γ-proteobacteria Methylotuvimicrobium buryatense, which has particular importance from the viewpoint of scalable biological gas to liquid processes for industrial application. A statistical design of experiments (at the serum bottle level) was used to optimize fermentation parameters. Enhancement in methanol accumulation was attempted using methanol dehydrogenase inhibitors. This was followed by a validation experiment run in a bioreactor at optimum conditions. At optimum conditions (pH = 7, phosphate concentration = 140 mM, temperature = 25°C) and optical density (600 nm) of 0.3, a methanol titer of 8.54 mM was achieved in 24 h (methane conversion = 20.8%). The addition of a methanol dehydrogenase inhibitor (0.5 mM Ethylenediaminetetraacetic acid) enhanced the methanol concentration to 10.37 mM. Experiments in a 3.7 L bioreactor using 1.68 bar headspace pressure and optical density (600 nm) of 0.1 yielded 23.7 mM methanol in 24 h (methane conversion = 47.8%). The methanol titers obtained using M. buryatense 5GB1C in 24 h fermentation are significantly higher than several previously reported methanotrophs. These results demonstrate the potential of M. buryatense 5GB1C for the biochemical synthesis of methanol.