title: An Approach for Lactulose Production Using the CotX-Mediated Spore-Displayed β-Galactosidase as a Biocatalyst.
abstract: Currently, enzymatic synthesis of lactulose, a synthetic prebiotic disaccharide, is commonly performed with glycosyl hydrolases. In this work, a new type of lactulose-producing biocatalyst was developed by displaying β-galactosidase from Bacillus stearothermophilus IAM11001 (Bs-β-Gal) on the surface of Bacillus subtilis 168 spores. Localization of β-Gal on the spore surface as a fusion to CotX was verified by western blot analysis, immunofluorescence microscopy, and flow cytometry. The optimum pH and temperature for the resulting spore-displayed β-Gal was 6.0 and 75°C, respectively. Under optimal conditions, it showed maximum activity of 0.42 U/mg spores (dry weight). Moreover, the spore-displayed CotX-β-Gal was employed as a whole cell biocatalyst to produce lactulose, yielding 8.8 g/l from 200 g/l lactose and 100 g/l fructose. Reusability tests showed that the spore-displayed CotX-β-Gal retained around 30.3% of its initial activity after eight successive conversion cycles. These results suggest that the CotX-mediated spore-displayed β-Gal may provide a promising strategy for lactulose production.
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, P.R. China.|Jiyang College, Zhejiang Agriculture and Forestry University, Zhuji 311800, P.R. China.
authors.forename: He
authors.initials: H
authors.lastname: Wang
authors.affiliation: School of Food Science and Technology, Jiangnan University, Wuxi 214122, P.R. China.
authors.forename: Ruijin
authors.initials: R
authors.lastname: Yang
authors.affiliation: School of Food Science and Technology, Jiangnan University, Wuxi 214122, P.R. China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Hua
authors.affiliation: School of Food Science and Technology, Jiangnan University, Wuxi 214122, P.R. China.
authors.forename: Wenbin
authors.initials: W
authors.lastname: Zhang
authors.affiliation: School of Food Science and Technology, Jiangnan University, Wuxi 214122, P.R. China.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhao
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D055162:Biocatalysis; D015964:Gene Expression Regulation, Bacterial; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007792:Lactulose / Q000096:biosynthesis*; D013171:Spores, Bacterial; D013696:Temperature; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C081620:cotX protein, Bacillus subtilis; D007792:Lactulose; D001616:beta-Galactosidase
keywords: Bacillus subtilis; CotX; Surface display; lactulose; spore; β-galactosidase