Comparative study of oxygen-limited and methane-limited growth phenotypes of Methylomicrobium buryatense 5GB1

摘要

Methylomicrobium buryatense 5 GB1 has been identified as a promising biocatalyst for industrial methane conversion to produce value-added products. However, despite recent advancements in understanding the metabolism of 5 GB1, existing knowledge on the differences between oxygen-limited and methane-limited phenotypes is still limited. In this work, both batch and continuous experiments were carried out to systematically examine the strain's oxygen-limited and methane-limited phenotypes. Total carbon balances were performed to ensure the obtained measurements of CH4 and O-2 consumption rates and CO2 production rate were accurate. Our results showed that the feed gas composition alone does not dictate the strain's growth phenotype. In order to achieve a desired phenotype, both feed gas composition and cell growth rate have to be controlled. In addition, contrary to the common belief that oxygen-limited conditions lead to increased production of organic compounds, our results suggest that it is the methane-limited condition that has higher yield for organic compounds. Knowledge of these differences could provide key understanding into how M. buryatense 5 GB1 regulate its carbon flow among different pathways under different growth conditions, which will provide the key insights for both mutant design and process design (e.g., culture conditions) for desired outcomes such as increased production of organic acids. Finally, using data collected in this work and those published in literature, we further validated a published genome-scale model under optimal growth condition. In addition, our results suggest that the current model lacks key metabolic routes to explain the surprisingly robust growth exhibited by the strain under wide substrate availability conditions.