Application and development of methanotrophs in environmental engineering

Abstract

Bioconversion by aerobic methanotrophs, with their relatively high selectivity for specific substance (i.e., methane), is a more efficient and cost-effective methanol production method compared to chemical processes. Aerobic methanotrophs oxidize methane to oxidize to methanol, then formaldehyde, followed by formate, and finally carbon dioxide via enzymatic reaction pathways. One of the intermediates of this process, methanol can be recovered by inhibiting enzymatic catalysis of methanol dehydrogenase while maintaining the activity of methane monooxygenase (MMO). Then, the biologically converted methanol is available for use in chemical or alternative fuel production, which, in turn, contributes to reducing greenhouse gas emissions, consequently completing allowable carbon resource circulation. Furthermore, methanotrophs decompose persistent organic pollutants, including halogenated hydrocarbons through MMO reaction. However, many studies have addressed the restrictions associated with methanotrophic oxidation, e.g., slow species growth rate, organic substance uptake limitations, and difficulty in controlling MMO and methanol dehydrogenase activities. Thus, there are additional incubation conditions for methanotrophs that require optimization such as methane and oxygen gas fractions, gas transfer rate to cells, and bioreactor design.