Ultrasound Induced Enhancement of Biological Gas-to-Liquid Process for Methanol Synthesis from Methane Using Methylotuvimicrobium buryatense 5GB1C

Abstract

Methanol is a potential alternate liquid transportation fuel. Conventional processes for methanol production from methane are energy-intensive. Microbial conversion of methane to methanol (Biological Gas-To-Liquid process) is a potential eco-friendly alternative. In this study, we have reported the intensification of methane fermentation to methanol (24 h batch mode) by Methylotuvimicrobium buryatense 5GB1C using 33 kHz sonication. The fermentation process was optimized for the sonication treatment time and duty cycle. A maximum titer of 20 mM (127.5 mg methanol/g dry cell weight biomass) was obtained in a 10 h sonication treatment at a 10% duty cycle, which was ∼57% higher than in control experiments. A mechanistic study of this result using pmoA gene expression (measured using qRT-PCR) and total protein analysis (sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)) revealed that the overexpression of the pmoA gene (therefore, pmoCAB operon) led to the overexpression of the particulate methane monooxygenase (pMMO) enzyme in the metabolic pathway of M. buryatense resulting in the production of pMMO in higher quantities than that in control experiments. The ultimate manifestation of these phenomena was faster enzyme kinetics and high methanol yield.