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 μM) and NaCl (0–9%) concentration as well as temperature (25–35 °C) on ectoine synthesis and specific CH₄ biodegradation rate was evaluated for the first time. Concentrations of 20% CH₄ (at 3% NaCl, 0.05 μM Cu²⁺, 25 °C) and 6% NaCl (at 4% CH₄, 0.05 μM Cu²⁺, 25 °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 μM), 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.