Effect of CH4/O2 ratio on fatty acid profile and polyhydroxybutyrate content in a heterotrophic–methanotrophic consortium

[Display omitted] •Enriched H–Meth consortium provided 15–20-fold higher CH4 oxidation rate than seed.•H–Meth was dominated by Methylocystis sp., Methylophaga and Pseudoxanthomonas.•Varying CH4 to O2 ratio affected the oxidation capacity of H–Meth.•Biopolymer and fatty acid contents were not affected by varying CH4/O2 ratio. Understanding the role of heterotrophic–methanotrophic (H–Meth) communities is important for improvement of methane (CH4) oxidation capacities (MOC) particularly in conjunction with bio-product development in industrial bio-filters. Initially, a H–Meth consortium was established and enriched from marine sediments and characterized by next generation sequencing of the 16s rDNA gene. The enriched consortium was subjected to 10–50% CH4 (i.e., 0.20–1.6 CH4/O2 ratios) to study the effects on MOCs, biomass growth, fatty acid profiles and biopolymer (e.g. polyhydroxybutyrate; PHB) content. Methylocystis, Methylophaga and Pseudoxanthomonas dominated the H–Meth consortium. Culture enrichment of the H–Meth consortium resulted in 15–20-folds higher MOC compared to seed sediments. Increasing CH4 concentration (and decreased O2 levels) yielded higher MOCs, but did not improve total fatty acid contents. PHB contents varied between 2.5% and 8.5% independently of CH4/O2 ratios. The results suggest that H–Meth consortia could potentially be used in industrial bio-filters for production of biopolymer/biofuel precursors from CH4.