Enzyme-Embedded, Microstructural Reactors for Industrial Biocatalysis

Enzymes must be integrated with functional materials to fully realize their potential in large-scale chemical processes. The specific challenges in energy applications for biocatalysis include (1) the need for very high volume and throughput, (2) the presence of gas-phase reactants or products, (3) the need to supply cofactors to the enzymes of interest, and (4) the requirement to remove products to maintain enzyme activity. We propose to develop new polymeric bioreactor materials that address these challenges. We will evaluate a polymeric bioreactor strategy using particulate methane mono-oxygenase cell membrane fragments from methanotroph cells. The only known catalysts for partial methane oxidation (CH4 → CH3OH (methanol)) under ambient conditions are mono-oxygenase enzymes from methanotrophic bacteria. Particulate methane monooxygenase (pMMO) is highly abundant in the cell membranes. Using membrane fragments, partial methane oxidation (conversion of methane to methanol) has been measured with activity of ~2000 nanomoles/micromole/min. The membrane-bound character of pMMO may be advantageous for concentrating methane (because methane is ~20X more soluble in lipids than in water), maintaining protein structure, and incorporating into a polymer. Therefore, for practical applications, optimized bioreactor elements containing pMMO appear to be a promising and highly relevant route to explore for both a proof-of concept bioreactor design and for gas to liquids applications. Professor Amy Rosenzweig of the Department of Molecular Biosciences at Northwestern University has 25 years experience cultivating methanotrophs and studying MMOs. She is internationally recognized as the foremost expert on pMMO biochemistry. Her research group has studied pMMO for the past 16 years, is the only group to date to crystallize and determine structures of pMMO, and recently identified the pMMO active site. She and her team will be integral to cultivating pMMO enzyme and providing expertise in enzyme structure-function relationships for this project. Her laboratory is fully equipped for methanotroph growth, membrane protein isolation and biochemistry, including purification, metal analysis, activity assays, kinetics, and protein crystallography. LLNL and Northwestern will collaborate on Objectives 1 and 2 for this project. Our study will provide a framework for general bioreactor design for gas to liquids processes using isolated enzymes.