期刊
FOOD CHEMISTRY
卷 207, 期 -, 页码 60-67出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.foodchem.2016.02.067
关键词
Lactulose; Cellobiose 2-epimerase; Activity improvement; Random mutagenesis
资金
- Fundamental Research Funds for the Central Universities [2662105QD030]
- Key Project of National Science Fund of China [31230057]
- National Key Technology RD Program [2011BAD23B03]
Industrial application of Caldicellulosiruptor saccharolyticus cellobiose 2-epimerase (CsCE) for lactulose synthesis is limited by low enzyme activity and formation of epilactose as by-product. After four sequential rounds of random mutagenesis and screening, an optimal mutant G4-C5 was obtained. Compared with wild type (WT) enzyme, mutant G4-C5 demonstrated 2.8-and 3.0-fold increases in specific activity and k(cat)/K-m for lactulose production, respectively, without compromising thermostability. DNA sequencing of mutant G4-C5 revealed five amino acid substitutions, namely, R5M, I52V, A12S, K328I and F231L, which were located on the protein surface, except for the mutation I52V. The yield of lactulose catalyzed by mutant G4-C5 increased to approximately 76% with no obvious epilactose detected, indicating that mutant G4-C5 was more suitable for lactulose production than the WT enzyme. (C) 2016 Elsevier Ltd. All rights reserved.
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