| Chitosan oligosaccharide(COS) is the oligomer of Chitosan,and it is composed of 2-20 N-glucosamines withβ-1,4, the molecular weight is under 10,000. COS is used widely in medicine, food, drink, and cosmetics industries, and its market value is far above other chitin products.Chitosan can be depolymerized into COS by specific or unspecific enzymes. The enzymic method has many merits:mild reaction conditions, higher hydrolysis efficiency, safer products etc. Furthermore, the degree of polymerization(DP) of products can be easily controlled, so it represents the direction of oligosaccharide synthesis.Meanwhile, cellulase can hydrolyze chitosan effectively and be easily gotten at low cost, as a result, it is becoming a popular hydrolase. Regarding this, in this paper the depolymerizing oligosaccharide conditions with cellulase obtained from Trichoderma virid were optimized and the quality assessment and antibacterial effects of hydrolysis products were studied.The cellulase used was made by Trichoderma virid from our laboratory(enzyme activity 7IU/mL), and the depolymerizing chitosan conditions with cellulose were studied. Using reducing sugar concentration in products, intrinsic viscosity of products and average DP as three indicators, the optimal conditions of hydrolyzing chitosan were gotten:reaction temperature 50℃, pH5.0, enzyme amount 6IU(per g of substrate), substrate concentration 3% and so on. With COS (DP 1-6) as guide sample, the hydrolysate was analyzed through TLC and mass spectrometry, and results showed that the hydrolysate included COS(DP 1-7). It turned out that cellulose could hydrolyze chitosan effectively.COS was prepared and separated according to enzyme hydrolysis-membrane separation coupling mechanism, by such a method, hydrolysate with narrow relative molecular mass distribution not only could be separated, but also hydrolyze substrates continuely using hydrolysase to improve hydrolysis efficiency. UF flux was related with operation pressure and UF time:when operation pressure was 0.40MPa and UF time was 3.5h, UF flux was constant. When hydrolysate was put through the hydrolysis membrane (molecular weight 10,000), hydrolysis products with an average molecular weight of 2,000 were gotten, and the hydrolysis rate was 40.5%.The physicochemical and functional properties of COS were studied, and such results were gotten:the average molecular weight of hydrolysis products was 1,485, deacetylation degree(D.D.) was 91.61%, water content was 6.5%, COS content was 81%, every aspect of hydrolysate all reached standard quality indexes; hydrolysate had a good water solubility under pH ranged from 1 to 13, however, the water solubility decreased a little when pH was above 8.0, COS could dissolve totally in 40% ethanol, and its solubility decreased as ethanol concentration increased; COS solution presented positive characteristic when pH was below 9.68; COS solution had a good stability when temperature was below 80℃; COS had excellent water holding capacity which was much better than glycerol, while its original substrate had a poor water holding capacity; COS was susceptible to maillaid braun reaction and should be stored in a dry and low temperature environment.In this paper, the inhibition of COS against E.coli and Trichoderma virid were tentatively discussed, and the relation between antibacterial activity and the COS concentration also was tentatively discussed. Such results were gotten:COS had a good bacteriostasis against E.coli and Trichoderma virid under acidic condition. However, COS didn't show an obvious inhibition against Aspergillus niger, even stimulated its growth, this was possibly because that Aspergillus niger could induce chitosanase.
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