| Chitinase can degrade chitin into chitin oligosaccharide. These oligosaccharide take an important part in hemostasis, anticoagulation, anti-tumor metastasis and inhance the growth of the beneficial microorganisms. Besides, it can induce the generation of cell factor, elevate the body immunity, stimulate the multiplication of collagenblast, bind with extracellular matrix, and facilitate tissue repair. Futhermore, oligosaccharide can antibiosis, antisepsis and keep moist. Therefore, chitin has a bright future in medicine and cosmetics industry.The overall goal of this research was to try to express gene chiA from Bacillus thuringiensis in Escherichia coli and Bacillus subtilis. Gene chiA had been cloned into Escherichia coli and Bacillus subtilis through the expressing vector pET-28a-chiA and pHSG- chiA individually, and the chitinase activity had been detected in the two kinds of recombinants. Enzymatic properties analysis of the recombinant chitinase of Bacillus subtilis (pHSG- chiA) revealed that an enzymatic activity optimum at pH 7.0, the chitinase was stable between pH 4 and pH 8. The optimal temperature for enzymatic activity was about 50℃, however, it had stable chitinase activity between 30℃and 60℃.Research on the stability of recombinant plasmids indicated that pET-28a-chiA was stable in the Escherichia coli, while plasmid lost during the transfer of culture of recombinant Bacillus subtilis (pHSG- chiA), and 50% plasmids had lost after the five times of transfer of culture without use of selection pressure. The fermentation conditions of recombinants were optimized. Carbon source, nitrogen source, incipient pH of the culture medium, volume of medium, inoculum size and inducing time analysis gave a optimum culture medium: chitin 2%, yeast extract 2.5%, NaCl 1%, K2HPO4 0.1%, MgSO4·7H2O 0.01%, incipient pH of the culture medium 8.0, volume of medium 20 mL/250 mL, 10% of inoculum size . And activity of the recombinant chitinase was up to 4.8 U/mL.
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