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Production and characterization of a thermostable chitinase from a new alkalophilic Bacillus sp. BG‐11
Author(s) -
Bhushan B.
Publication year - 2000
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1046/j.1365-2672.2000.01016.x
Subject(s) - chitinase , bacillus (shape) , microbiology and biotechnology , bacillaceae , biology , food science , library science , bacteria , gene , biochemistry , genetics , computer science , bacillus subtilis
An alkalophilic, environmental micro‐organism, Bacillus sp. BG‐11, has been isolated and characterized. It produced 76 U ml −1 of chitinase in liquid batch fermentation after 72 h of incubation at 50 °C using chitin‐enriched medium. The molecular weight of purified chitinase was estimated to be 41 kDa by SDS–PAGE. The pH and temperature optima of chitinase immobilized on chitosan and calcium alginate were 8·5 and 50 °C, respectively, which were same as that of free enzyme. The pH and thermostability of immobilized chitinase were enhanced significantly. The chitinase immobilized on chitosan was stable between pH 5·0 and 10·0, and the half‐life of chitosan‐immobilized enzyme at 70, 80 and 90 °C was 90, 70 and 60 min, respectively. The end‐products formed during the enzyme–substrate reaction were identified by 13 C‐NMR, and N ‐acetyl‐ d ‐glucosamine was found to be the major end‐product. GlcNAc (GlcNAc) 2 and (GlcNAc) 3 inhibited the chitinase activity by 32, 25 and 18%, respectively, at a concentration of 10 mmol l −1 . The shelf‐life of chitinase (retained 100% activity) at 4 °C was 8 weeks in the presence of either sodium azide (100 µg ml −1 ), sodium metabisulphite (0·1% w/v) or KCl (15% w/v). The enzyme was resistant to the action of proteases and allosamidin.