芽孢杆菌BC-X5产壳聚糖酶的表征及壳寡糖制备研究OA

The yield of chitosan oligosaccharides(COS)produced by enzymatic hydrolysis can be enhanced by optimizing both the enzyme characteristics and the selection of suitable substrates.In this study,a chitosanase with an approximate molecular weight of 40 kDa was purified from the fermentation broth of a Bacillus strain using ammonium sulfate precipitation,DEAE FF 16/10,and Superdex 75 10/300 GL column chromatography.The enzyme exhibited optimal activity at pH 5.5 and remained stable between pH 5.0 and 7.0.Its highest activity was observed at 55 ℃,with stability maintained from 30 ℃ to 55 ℃.Thin-layer chromatography analysis revealed that the enzyme hydrolyzed chitosan and COS with a degree of polymerization greater than four,producing primarily(GlcN)2,(GlcN)3,and(GlcN)4.Additionally,two commercially available chitosan powders were utilized to prepare a series of substrates,which were characterized by Fou-rier transform infrared spectroscopy,X-ray diffraction and gel permeation chromatography.Post-reaction analysis indicated that the chitosan substrate with approximately 80％deacetylation and a molecular weight of 100 000 yielded the highest concentration of oligosaccharides:(GlcN)2 at 1.112 mg/mL,(GlcN)3 at 1.636 mg/mL,and(GlcN)4 at 0.824 mg/mL.These findings suggest that the enzyme's efficien-cy is influenced by the substrate's molecular weight and deacetylation degree.This study provides valuable insights for optimizing enzymat-ic processes in the industrial production of COS.