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Applied and Environmental Microbiology, April 2007, p. 2251-2256, Vol. 73, No. 7
0099-2240/07/$08.00+0     doi:10.1128/AEM.01489-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Transgalactosylation in a Water-Solvent Biphasic Reaction System with ß-Galactosidase Displayed on the Surfaces of Bacillus subtilis Spores

Seok Joon Kwon,^1, Heung-Chae Jung,^1,2, and Jae-Gu Pan^1,2*

GenoFocus, Inc., 461-58 Jeonmindong, Yusong, Daejeon 305-811,¹ Systems Microbiology Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), 52 Oundong, Yusong, Daejeon 305-333, Korea²

Received 30 July 2006/ Accepted 13 December 2006

The ever-increasing industrial demand for biocatalysis necessitates innovations in the preparation and stabilization of biocatalysts. In this study, we demonstrated that ß-galactosidase (ß-Gal) displayed on Bacillus spores by fusion to the spore coat proteins (CotG) may be used as a whole-cell immobilized biocatalyst for transgalactosylation in water-solvent biphasic reaction systems. The resulting spores had a specific hydrolytic activity of 5 x 10³ U/g (dry weight) of spores. The ß-Gal was tightly attached to the spore surface and was more stable in the presence of various organic solvents than its native form was. The thermostability of the spore-displayed enzyme was also increased, and the enzyme was further stabilized by chemically cross-linking it with glutaraldehyde. With spore-displayed ß-Gal, octyl-ß-D-galactopyranoside was synthesized at concentrations up to 27.7 mM (8.1 g/liter) with a conversion yield of 27.7% (wt/wt) after 24 h from 100 mM lactose and 100 mM octanol dissolved in phosphate buffer and ethyl ether, respectively. Interestingly, the spores were found to partition mainly at the interface between the water and solvent phases, and they were more available to catalysis between the two phases, as determined by light microscopy and confocal fluorescence microscopy. We propose that spore display not only offers a new and facile way to construct robust biocatalysts but also provides a novel basis for phase transfer biocatalytic processes.

Published ahead of print on 22 December 2006.

S.J.K. and H.-C.J. contributed equally to this work.

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