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Biocatalysis for the synthesis of polymer precursors  

The U.S. Air Force Material Science directorate has identified the compounds m-hydroxybiphenyl (m-HBP) and m-hydroxydiphenylacetylene (m-HDPA) as critical precursors in the production of high performance polymers.  Epoxy resins synthesized using m-HBP or m-HDPA have exceptional thermal resistance and could be used in a number of important aerospace applications. While m-HBP and m-HDPA are difficult to produce by normal chemical synthesis, biocatalysis may offer an alternative method.  Research by Dr. Glenn Johnson at Tyndall AFB, FL has identified two bacterial enzymes that are capable of producing either m-HBP from biphenyl or m-HDPA from diphenyl acetylene (DPA).In these studies, product purities as high as 90% were observed.  Unfortunately, the reaction rates were quite low, due in part to the low aqueous solubility of biphenyl and DPA. Chemical reaction rates are generally proportional to the concentration of reactant in solution. 

Fed-batch operation of a bioreactor to grow recombinant  E. coli expressing a foreign gene

Bioreactor, control unit & computer control station used in biochemical engineering lab.

To increase biocatalysis rates for these compounds, the effective concentration of enzyme and/or substrate in solution must be increased. While Dr. Johnson has developed an  E. coli strain that will over express the genes that encode for our desired enzymes, the culture environment can have a significant effect on the actual amount of enzyme produced. Jason Herr is currently evaluating fed-batch strategies for the production of high cell density E. coli cultures.By increasing the cell density prior to induction,we hope to maximize the overall enzyme concentration in solution.  Conversely, Sowmya Talari is trying to increase the effective substrate concentration in aqueous solution through the addition of surfactants.  Certain surfactants are toxic to specific bacterial species; thus, we are screening a variety of surfactant compounds to determine the optimal one for our particular biocatalysis system. 

High Performance Liquid Chromatography (HPLC) is used extensively in our research for the quantification of various compounds in our fermentations.

This research is supported by the Air Force Research Laboratory through the DoD-EPSCoR program