Effects of salts on activity of halophilic cellulase with glucomannanase activity isolated from alkaliphilic and halophilic Bacillus sp. BG-CS10 |
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Authors: | Guimin Zhang Shunyi Li Yanfen Xue Liangwei Mao Yanhe Ma |
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Institution: | (1) State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China;(2) College of Life Sciences, Hubei University, Wuhan, 430062, China; |
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Abstract: | Alkaliphilic and halophilic Bacillus sp. BG-CS10 was isolated from Zabuye Salt Lake, Tibet. The gene celB, encoding a halophilic cellulase was identified from the genomic library of BG-CS10. CelB belongs to the cellulase superfamily
and DUF291 superfamily, with an unknown function domain and less than 58% identity to other cellulases in GenBank. The purified
recombinant protein (molecular weight: 62 kDa) can hydrolyze soluble cellulose substrates containing beta-1,4-linkages, such
as carboxylmethyl cellulose and konjac glucomannan, but has no exoglucanase and β-glucosidase activities. Thus, CelB is a
cellulase with an endo mode of action and glucomannanase activity. Interestingly, the enzyme activity was increased approximately
tenfold with 2.5 M NaCl or 3 M KCl. Furthermore, the optimal temperatures were 55°C with 2.5 M NaCl and 35°C without NaCl,
respectively. This indicates that NaCl can improve enzyme thermostability. The K
m
and k
cat values of CelB for CMC with 2.5 M NaCl were 3.18 mg mL−1 and 26 s−1, while the K
m
and k
cat values of CelB without NaCl were 6.6 mg mL−1 and 2.1 s−1. Thus, this thermo-stable, salt and pH-tolerant cellulase is a promising candidate for industrial applications, and provides
a new model to study salt effects on the structure of protein. |
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Keywords: | |
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