Valorization of CH4 emissions into high-added-value products: Assessing the production of ectoine coupled with CH4 abatement

This study assessed an innovative strategy for the valorization of dilute methane emissions based on the bio-conversion of CH4 (the second most important greenhouse gas (GHG)) into ectoine by the methanotrophic ectoine-producing strain Methylomicrobium alcaliphilum 20 Z. The influence of CH4 (2-20%), Cu2+ (0.05-50 mu M) and NaCl (0-9%) concentration as well as temperature (25-35 degrees C) on ectoine synthesis and specific CH4 biodegradation rate was evaluated for the first time. Concentrations of 20% CH4 (at 3% NaCl, 0.05 mu M Cu2+, 25 degrees C) and 6% NaCl (at 4% CH4, 0.05 M Cu2+, 25 degrees C) supported the maximum intra-cellular ectoine production yield (31.0 +/- 1.7 and 66.9 +/- 4.2 mg g biomass(-1), respectively). On the other hand, extra-cellular ectoine concentrations of up to 4.7 +/- 0.1 mg L-1 were detected at high Cu2+ concentrations (50 mu M), despite this methanotroph has not been previously classified as an ectoine-excreting strain. This research demonstrated the feasibility of the bio-conversion of dilute emissions of methane into high-added value products in an attempt to develop a sustainable GHG bioeconomy. CO (C) 2016 Elsevier Ltd. All rights reserved.