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Applied and Environmental Microbiology, October 2009, p. 6545-6552, Vol. 75, No. 20
0099-2240/09/$08.00+0     doi:10.1128/AEM.00434-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Whole-Cell Biocatalysis for 1-Naphthol Production in Liquid-Liquid Biphasic Systems{triangledown}

S. V. B. Janardhan Garikipati, Angela M. McIver, and Tonya L. Peeples*

Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa 52242

Received 20 February 2009/ Accepted 11 August 2009

Whole-cell biocatalysis to oxidize naphthalene to 1-naphthol in liquid-liquid biphasic systems was performed. Escherichia coli expressing TOM-Green, a variant of toluene ortho-monooxygenase (TOM), was used for this oxidation. Three different solvents, dodecane, dioctyl phthalate, and lauryl acetate, were screened for biotransformations in biphasic media. Of the solvents tested, lauryl acetate gave the best results, producing 0.72 ± 0.03 g/liter 1-naphthol with a productivity of 0.46 ± 0.02 g/g (dry weight) cells after 48 h. The effects of the organic phase ratio and the naphthalene concentration in the organic phase were investigated. The highest 1-naphthol concentration (1.43 g/liter) and the highest 1-naphthol productivity (0.55 g/g [dry weight] cells) were achieved by optimization of the organic phase. The ability to recycle both free cells and cells immobilized in calcium alginate was tested. Both free and immobilized cells lost more than ~60% of their activity after the first run, which could be attributed to product toxicity. On a constant-volume basis, an eightfold improvement in 1-naphthol production was achieved using biphasic media compared to biotransformation in aqueous media.

* Corresponding author. Mailing address: Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, IA 52242. Phone: (319) 335-2251. Fax: (319) 353-1415. E-mail: tonya-peeples{at}uiowa.edu

{triangledown} Published ahead of print on 21 August 2009.

Applied and Environmental Microbiology, October 2009, p. 6545-6552, Vol. 75, No. 20
0099-2240/09/$08.00+0     doi:10.1128/AEM.00434-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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