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Biotechnology and Applied Biochemistry (2003) 38, (131–136) (Printed in Great Britain)

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Enhanced expression of the gene for b-glycosidase of Thermus caldophilus GK24 and synthesis of galacto-oligosaccharides by the enzyme

Jeong Jin Choi*, Eun-Joo Oh*, Yoon-Jin Lee*, Dong Sang Suh*, Jae Heung Lee†, Soo-Won Lee†, Hyung-Tai Shin† and Suk-Tae Kwon*¹

*Department of Genetic Engineering, Sungkyunkwan University, 300 Chunchun-Dong, Jangan-Ku, Suwon 440-746, South Korea, and †Department of Food and Life Science, Sungkyunkwan University, 300 Chunchun-Dong, Jangan-Ku, Suwon 440-746, South Korea

Key words: galactosyl-transfer activity, gene expression, Thermus caldophilus GK24 b-glycosidase.

Abbreviations used: pNPGal, p-nitrophenyl b-D-galactopyranoside; Tca b-glycosidase, Thermus caldophilus GK24 b-glycosidase.

¹To whom correspondence should be addressed (e-mail stkwon@yurim.skku.ac.kr).

The gene (bglT) encoding Tca b-glycosidase (Thermus caldophilus GK24 b-glycosidase) was overexpressed under the control of the trp promoter on a high-copy-number plasmid, pTRPES, in Escherichia coli W3110. The purified Tca b-glycosidase enzyme was used in a galactosyl-transfer reaction to synthesize galacto-oligosaccharides from lactose. The optimum temperature and pH for the enzyme to synthesize galacto-oligosaccharides from 30% (w/v) lactose were 80 °C and 6.0, respectively. The major product of the reaction was a trisaccharide. The thermostable Tca b-glycosidase produced galacto-oligosaccharides efficiently during the hydrolysis of lactose.

Received 12 December 2002/3 April 2003; accepted 15 May 2003

Published as Immediate Publication 15 May 2003, DOI 10.1042/BA20020119

© 2003 Portland Press Ltd