Progress 07/01/02 to 09/30/04
Outputs
Enzymes are fundamental to all life on earth. They facilitate all biologically important chemical reactions and are for example essential to handling information and energy in all living organisms. Products derived from inexpensive agricultural byproducts by enzymatic catalysis can be labeled as "natural" which is a significant incentive for the consumer. These products command a much higher price than identical chemicals made using conventional chemical catalysis. However, such new natural products can often only be made in organic solvents where the reactants and products are both soluble. The dissolved water content is crucial for enzymatic reactions in solvents. The technical feasibility of sensing and simultaneously controlling dissolved water in an organic solvent was conclusively shown in laboratory experiments. Commercial enzyme preparations were used to produce a fragrance in the solvent hexane from a byproduct of wood pulping. The optimum reaction conditions
were determined. These results will aid in the use of enzymatic reactions to produce high-value natural flavors and fragrances from inexpensive agricultural feedstocks. Our new technology also allows to investigate the fundamentals of enzymatic catalysis in solvents at controlled water contents, which may lead to new information regarding the function of enzymes.
Impacts
The impact of the proposed work is to develop processing tools for efficient technical scale bioprocessing of agricultural feedstocks to high value added natural products using enzymatic catalysis. This work will remove technical barriers to producing natural high value-added products such as flavors, fragrances, and pharmaceuticals from agricultural feedstocks.
Publications
- Kang, I.-J., Rezac, M. E., Pfromm, P. H., "Membrane permeation based sensing for dissolved water in organic micro-aqueous media", Journal of Membrane Science, 239/2, 213-217, 2004
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Progress 01/01/03 to 12/31/03
Outputs
Nevertheless, we are on-schedule with significant achievements on all of the original objectives. To summarize the results to date that are detailed below, the laser interferometric sensor for dissolved water in organics shows promise and we continue development as proposed. In addition, a membrane permeation based water sensor has been developed and tested in batch reactor runs for gram-scale enzymatic production of geranyl acetate while actively controlling the water concentration via membrane pervaporation. Initial kinetic data with water concentration control and continuous sensing of the thermodynamic water activity by our membrane sensor is shown below. 1. Develop an on-line sensor for the water content of micro-aqueous organic fluids and fluid mixtures. We evaluated two separate approaches for measuring the concentration of dissolved water in n-hexane. The first was based on a laser interferometric principle. The second was based on a selective membrane
permeation process. Both showed good results. The membrane sensor proved to require less instrumentation and up to now provided more stable results over the entire range of water concentrations of interest. Sensor response times are on the order of seconds. To date, we have detected no problems with interference from other solution components. We have worked extensively with water/organic systems. 2. Develop a thin film composite pervaporation membrane. We have used cellulose acetate/ceramic composite membranes made by kiss-coating of cellulose acetate solutions in acetone on a commercial ceramic substrate up to now Defect-free cellulose acetate films on the order of 1 micrometer thickness or less have been produced. 3. Test the performance of the combination of the new sensor and the continuous water removal for a model reaction on the laboratory scale. In this work, we demonstrated that the membrane permeation system could be used to rapidly and accurately increase or decrease the
concentration of water in the system. The rate of reaction for enzymatically catalyzed geraniol conversion to geranyl acetate was measured at water concentrations of 13 and 16 ppm. Even the minor change in water activity in n-hexane (3ppm) had an impact on the initial rate of reaction. We can now explore the exact influence of the water thermodynamic activity (constant throughout the reaction) on the reaction kinetics. Issues such as enzyme lifetime and reversibility (cycling) of the water activity will be investigated.
Impacts
Process technology for the rapid and facile control of the water activity in organic liquids has been developed. The technology is being employed to demonstrate the importance of water content on the kinetic activity of enzymes in organic media.
Publications
- Kang, I.-J., Rezac, M. E. and Pfromm, P. H. "Membrane permeation based sensing for dissolved water in organic micro-aqueous media", Journal of Membrane Science (submitted June 2003, accepted January 2004).
- Kang, I.-J., Rezac, M. E. and Pfromm, P. H., "Sensing of Water in Microaqueous Solvents by Highly Selective Membrane Permeation", AIChE National Meeting, San Francisco, CA, paper 334b, November 18, 2003.
- Bartling, K., Thompson, J., Pfromm, P, Rezac, M., Czermak, P., "Membrane-reactor systems for the selective control of water activity in lipase-catalyzed esterifications", Grenada, Spain, 2001.
- Bartling, K., Thompson, J., Pfromm, P. H., Rezac, M. E., Czermak, P., "Biocatalytic membrane reactor – application of pervaporation for improved enzyme-catalyzed esterification of geraniol in the organic phase", Dechema Section Membrane Technology, Frankfurt, Germany, 2001.
- Bartling, K., Thompson, J. U. S., Pfromm, P. H., Rezac, M.E. and Czermak, P., "Einsatz der Pervaporation zur Verbesserung der enzymkatalysierten Esterifikation von Geraniol in der organischen Phase," Aachener Membran Kolloquium, Preprints 8, pg. II93-II96, Verlag Mainz, Aachen 2001, ISBN 3-89653-834-9, 2001.
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