Ammonium influences kinetics and structure of methanotrophic consortia

Abstract

The literature is conflicted on the influence of ammonium on the kinetics and microbial ecology of methanotrophy. In this study, methanotrophic cultures were enriched, under ammonium concentrations ranging from 0 to 200 mM, from an inoculum comprising leachate and top-cover soil from a landfill. Specific CH 4 biodegradation rates were highest (7.8 × 10 −4 ± 6.0 × 10 −5 gCH 4 g X−1 h −1 ) in cultures enriched at 4 mM NH 4+ , which were mainly dominated by type II methanotrophs belonging to Methylocystis spp. Lower specific CH 4 oxidation rates (average values of 1.8–3.6 × 10 −4 gCH 4 g X−1 h −1 ) were achieved by cultures enriched at higher NH 4+ concentrations (20 and 80 mM), and had higher affinity for CH 4 compared to 4 mM enrichments. These lower affinities were attributed to lower diversity dominated by type I methanotrophs, of the Methylosarcina, Methylobacter and Methylomicrobium genera, encountered with increasing concentrations of NH 4+ . The study indicates that CH 4 oxidation biotechnologies applied at low NH 4+ concentrations can support efficient abatement of CH 4 and high diversity of methanotrophic consortia, whilst enriching type II methanotrophs.