Most chemical reactions of interest for clean energy are routinely carried out in nature. These reactions include the conversion of sunlight to chemical energy, the transfer of carbon dioxide into and out of solution, the selective oxidation of hydrocarbons (including methane to methanol), the formation of C-C bonds (including methane to ethylene), and the formation and dissolution of Si-O bonds (including enhanced mineral weathering).
Conventional industrial approaches to catalyze these reactions are either inefficient or have yet to be developed. However, certain enzymes have been identified that carry out each of these reactions with high selectivity under mild conditions. This presents an opportunity for industrial biocatalysis and biomimetics to fill the gap between current technology and natural capabilities.
With some notable exceptions in the food and detergent markets, industrial biocatalysis is primarily limited to the synthesis of low-volume, high-value products, such as pharmaceuticals. This is due to the narrow range of operating parameters required to preserve biocatalyst activity. The reactions are typically carried out in single-phase, usually aqueous, media and suffer from slow rates of throughput due to low catalyst loading and limited mass transfer.
To allow reuse of enzymes in stirred-tank reactors, and to improve stability of enzymes in reactor conditions, enzymes have previously been immobilized on a variety of materials (silicas, polymers, ferrous nanoparticles) using a variety of techniques. The enzymes have almost exclusively been immobilized on inert materials and almost exclusively on the surfaces or in surface-accessible pores of the materials.
The core innovation of LLNL's enzyme-embedded, multi-component polymer-based bioreactors perform one or more additional functions of the bioreactor:
- efficient distribution of reactants and removal of products
- exposure of enzymes to high concentrations of gas-phase reactants
- separation of products and reactants
- formation of high surface area structures for exposing enzyme to reactants
- supply of electrons in hybrid enzyme-electrochemical reactions
- consolidation of enzymes with co-enzymes in nanoscale subdomains for chained reactions
Enzymes are embedded throughout the depth of the material instead of on the surface or in surface-accessible pores.
LLNL's enzyme-embedded polymer technology encompasses several methods to stabilize cell-membrane-bound enzymes. Enzymes can be incorporated into polymers by several methods depending on the application.
A major advantage of polymer-based materials for biocatalysis is the ability to shape and assemble the material into reactor components using conventional and advanced (additive) manufacturing techniques. Livermore's bioreactors based on enzyme-embedded multi-component polymers technology allows the more-efficient and higher-throughput use of enzymes in industrial applications.
LLNL's enzyme-embedded, multi-component polymer-based bioreactors have many applications in energy conversion, chemicals, food science, and pharmaceuticals. Uses of LLNL's bioreactors based on enzyme-embedded multi-component polymers technology include fuel conversion (e.g. natural gas to liquid fuel), chemical production, pharmaceutical production, and other processes where a chemical conversion is catalyzed by enzymes, especially at phases boundaries (e.g. reactions involving a gas and a liquid).
This technology is especially suited to reactions that take place at phase boundaries: gas to liquid, liquid to gas, polar to non-polar, non-aqueous to aqueous, etc. Many application in energy involve a gas-phase reactant or product, e.g. methane to methanol, CO2 absorption, oxidation reactions with O2, reduction reactions with H2 or methane, and CO2 conversion to synthetic fuel. Many reactions in the chemical and pharmaceutical industries involve treatment of non-polar organic compounds with polar reactants or vice versa.