Immobilization of methane monooxygenase in polyvinyl alcohol hydrogels for enhanced methanol production: Insights into catalytic efficiency and industrial applicability

The utilization of sphingomonas-MT for the isolation of methane monooxygenases (MMO) has garnered significant attention due to the growing focus on selective activation of methane under moderate conditions, particularly for utilizing new sources of natural gas pollution, for controlling its emission in the environment. This study explores the immobilization of soluble methane monooxygenase (sMMO) within polyvinyl alcohol (PVA) hydrogel matrices, evaluating its catalytic performance, stability, and reusability to optimize the conversion of methane to methanol. Methane concentration less than 2±0.5 g/L was found to be suitable for a higher methanotrophic growth rate (0.075±0.5 h -1 ) and sMMO production (2.5 ± 0.25 U) after 48 hours. The polyvinyl alcohol immobilized soluble methane monooxygenase (PVA-sMMO) displayed the highest immobilization yield and immobilization efficiency of 78.20±1.10%, and 86.40±1.25%, respectively, under optimum conditions. The PVA-sMMO exhibits the highest activity (610±1.15 Ug -1 of PVA) and RSM analysis identified the optimal conditions for maximum enzyme activity as follows: temperature 38 °C, pH 7.72, inoculum size 3.8 mL, and a carbon-to-nitrogen (C: N) ratio 0.58, ensuring the robustness of PVA-sMMO in industrial processes. A high value of (1.44 mM) for PVA-sMMO and superior reusability of about 70% after ten cycles, highlight the potential for sustained methanol production. EDX spectra confirmed the successful covalent immobilization of sMMO on the gel. The study also tracked methanol production over time, revealing consistent yields and highlighting the potential of PVA-immobilized sMMO for continuous, sustainable enzymatic processes. The improved stability and reusability of the PVA-sMMO system enhance its suitability for large-scale applications, meeting the rising demand for eco-friendly and efficient methane conversion technologies. • sMMO was successfully immobilized in PVA hydrogel with high efficiency. • Optimal enzyme activity achieved at 37 °C, pH 7.5, C:N ratio 0.5 and inoculum size 4%. • PVA-sMMO showed peak activity of 610 U g -1 under optimized conditions. • High K m (1.44 mM) and reusability after 10 cycles support its promising stability. • Methanol production remained stable, which enables a sustainable bioconversion.