A highly efficient and versatile genetic engineering toolkit for a methanotroph-based biorefinery

•Methane conversion to a value-added mevalonate using methanotrophs as biocatalysts.•A powerful and tunable synthetic biology toolkit for methanotrophs was developed.•CRISPR base editor enabled the efficient markerless single-step genome editing.•A significantly high production of mevalonate (2,090 mg/L) was achieved.•These versatile tools can realize the efficient methanotrophic biorefineries.