Honeycomb monolith-based multichannel reactor for methane bioconversion into ectoine

A novel gas-liquid multichannel bioreactor based on cordierite honeycomb monoliths was engineered and operated under internal gas and liquid recirculation for methane bioconversion into ectoine. The assessment of the volumetric gas-liquid mass transfer coefficients for O₂ ( [Formula: see text] ) in this novel bioreactor showed values up to 1472.7 ± 111.6 h^-1, representing an increase of one order of magnitude over conventional bubble column reactors. Bubble measurements were consistent with a flow regime compatible with Taylor-flow operation, suggesting that liquid-film renewal was likely a major contributor to mass-transfer enhancement. During diluted-methane bioconversion into ectoine, stable operation at relatively high gas and liquid recirculation rates was achieved after gradual enrichment of the halotolerant mixed methanotrophic culture, potentially because of the associated hydrodynamic shear stress. After inoculum adaptation, methane bioconversion efficiencies and capacities of up to 72.9% and 45 g m³ h^-1, with an ectoine concentration of 32.1 mg gVSS^-1, were achieved when operating with a gas residence time of 30 min, and gas and liquid recirculation of 40 L min^-1 and 25 L min^-1, respectively (corresponding to a [Formula: see text] of 679.5 ± 57.3 h^-1). Process performance was supported by a well-adapted inoculum dominated by Methylophaga, Methylonatrum and Methylotuvimicrobium, which accumulated 44% of the relative abundances. Monoliths as microchannels in high gas-liquid mass transfer reactors represent a promising platform for methane valorisation, but further optimisation of operational parameters is required to intensify ectoine production from methane.