Synthesizing value-added products from methane by a new Methylomonas.

Abstract

Methane and methanol are potential carbon sources of industrial micro-organisms in addition to crop-derived bio-carbon sources. Methanotrophs that can utilize these simple, stable and large amounts chemicals are expected to be developed into 'cell factories' for the production of specific chemicals. In this study, a methanotroph that can synthesize lycopene, C30 carotenoid and exopolysaccharides (EPS) with relative better performances from C1 substrates was isolated, and its performances were evaluated. The isolated strain was identified as Methylomonas sp. ZR1 based on 16S rRNA sequence analysis. Its maximum specific growth rate achieved 0·200h-1 under flask culture conditions, and 0·386h-1 in bubble column reactors. ZR1 was able to utilize 35gl-1 of methanol and even exhibited slight growth in the presence of 40gl-1 of methanol. Furthermore, ZR1 was proved to synthesize lycopene (C40 carotenoids) besides the C30 carotenoids through HPLC-DAD and HPLC-MS/MS analysis methods. Its carotenoid extracts exhibited excellent antioxidative activities measured by the ABTS+ method. Plenty of polysaccharides were also synthesized by ZR1, the components of the polysaccharides were identified as glucose, mannose and galactose with a proportion of 1:2:1 by GC-MS, and its yield achieved 0·13gg-1 cell dry weight. The isolated strain has great potential for the production of value-added bioproducts from C1 compounds because of its excellent C1 substrate utilizing abilities and its abilities to naturally synthesize lycopene, C30 carotenoids and EPS. In this study, we isolated a fast-growing methanotroph, its C1 carbon substrate utilizing ability is excellent in comparison with reported methanotrophs. Furthermore, besides polysaccharides and C30 carotenoids which were commonly synthesized by methanotrophs, our findings suggested that C40 lycopene could also be naturally synthesized from methane by methanotrophs.