Effects of salts on activity of halophilic cellulase with glucomannanase activity isolated from alkaliphilic and halophilic Bacillus sp. BG-CS10.
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.
State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
Guimin
G
Zhang
Shunyi
S
Li
Yanfen
Y
Xue
Liangwei
L
Mao
Yanhe
Y
Ma
D001407:Bacillus / Q000201:enzymology* / Q000235:genetics; D001483:Base Sequence; D002480:Cellulase / Q000302:isolation & purification / Q000378:metabolism*; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D004795:Enzyme Stability; D006868:Hydrolysis; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism
D017931:DNA Primers; D011994:Recombinant Proteins; D002480:Cellulase