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

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.