Sunday, May 4, 2008
2-22

Effects of overexpression of NADPH-regenerating glucose 6-phosphate dehydrogenase on caprolactone production in recombinant Escherichia coli harboring cyclohexanone monooxygenase gene

Won-Heong Lee, So Y. Shin, Young-Kyung Park, Hye-Jung Shin, and Jin-Ho Seo. Department of Agricultural Biotechnology, Seoul National University, San 56-1, Shillim-dong, Kwanak-gu, Seoul, South Korea

Caprolactone is an important intermediate compound for production of medical devices, food packages and bio-degradable plastics. As cyclohexanone monooxygenase (CHMO) converts cyclohexanone to caprolactone using NADPH, NADPH might be a critical factor for enhanced production of caprolactone. Whole-cell conversion of cyclohexanone to caprolactone was attempted by recombinant Escherichia coli BL21 (DE3) expressing cyclohexanone monooxygenase (CHMO) of Acinetobacter calcoaceticus NCIMB 9871. High concentrations of cyclohexanone and caprolactone reduced CHMO-mediated bioconversion of cyclohexanone to caprolactone in the recombinant E. coli cells. The metabolically active cells were employed by adopting a fed-batch culture to improve the production of caprolactone from cyclohexanone. A glucose-limited fed-batch Baeyer Villiger oxidation where a cyclohexanone level was maintained less than 6 g/l resulted in a maximum caprolactone concentration of 11.0 g/l. The maximum caprolactone concentration was improved further to 15.3 g/l by coexpression of glucose-6-phosphate dehydrogenase, an NADPH-generating enzyme encoded by the zwf gene which corresponded to a 39% enhancement in caprolactone concentration compared with the control experiment performed under the same conditions.

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