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Applied and Environmental Microbiology, September 2009, p. 5938-5942, Vol. 75, No. 18
0099-2240/09/$08.00+0     doi:10.1128/AEM.00326-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Cell Surface Engineering of a β-Galactosidase for Galactooligosaccharide Synthesis{triangledown}

Yumei Li,1,{dagger} Lili Lu,1,{dagger} Hongmei Wang,2 Xiaodong Xu,1 and Min Xiao1*

State Key Laboratory of Microbial Technology, National Glycoengineering Research Center, Shandong University, Jinan 250100, People's Republic of China,1 Department of Life Sciences, Zaozhuang College, Zaozhuang 277100, People's Republic of China2

Received 10 February 2009/ Accepted 12 July 2009

A novel gene encoding transglycosylating β-galactosidase (BGase) was cloned from Penicillium expansum F3. The sequence contained a 3,036-bp open reading frame encoding a 1,011-amino-acid protein. This gene was subsequently expressed on the cell surface of Saccharomyces cerevisiae EBY-100 by galactose induction. The BGase-anchored yeast could directly utilize lactose to produce galactooligosaccharide (GOS), as well as the by-products glucose and a small quantity of galactose. The glucose was consumed by the yeast, and the galactose was used for BGase expression, thus greatly facilitating GOS synthesis. The GOS yield reached 43.64% when the recombinant yeast was cultivated in yeast nitrogen base-Casamino Acids medium containing 100 g/liter initial lactose at 25°C for 5 days. The yeast cells were harvested and recycled for the next batch of GOS synthesis. During sequential operations, both oligosaccharide synthesis and BGase expression were maintained at high levels with GOS yields of over 40%, and approximately 8 U/ml of BGase was detected in each batch.

* Corresponding author. Mailing address: State Key Laboratory of Microbial Technology, National Glycoengineering Research Center, Shandong University, Jinan 250100, People's Republic of China. Phone and fax: 86 531 88365128. E-mail: minxiao{at}sdu.edu.cn

{triangledown} Published ahead of print on 17 July 2009.

{dagger} Y.L. and L.L. contributed equally to this work.

Applied and Environmental Microbiology, September 2009, p. 5938-5942, Vol. 75, No. 18
0099-2240/09/$08.00+0     doi:10.1128/AEM.00326-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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