Selective digestion of dextran by microbial dextranase for biomedical uses

摘要

8 strains with higher specific activity of dextranase were selected from soils of 4 provinces in Central and Southern China, belonged to bacteria, fungi and actinomyces. The natural dextran of higher molecular weight (Mw) formed by Leuconostoc mesenteroides AYC-F from sucrose can be partially digested by the dextranase-containing culture broth of these microbes to produce almost selective homogeneous fragments with different ratio of different typical Mw range of 1.0 +- 0.5 x 10~4, 2.0 +- 0.5 x 10~4, 4.0 +-0.5 x 10~4, 7.0 +- 0.5 x 10~4, 1.0 +- 0.5 x 10~5 etc. in the products mixture. To improve the quality of digested dextran in view of both particular Mw and no containminent of exogeneous proteins from microbes, two attempts were made, i.e.(1) mixculture of dextran-producing strain Leuconostoc mesenteroides AYC-F with dextranase-producing strain Penicillium sp AYC-4 and (2) immoblization of dextranase isozyme I from strain AYC-4. The particular Mw 7.0 +- 0.5 x 10~4 fragment with dominance could be specifically obtained under these two ways from the selective digestion of natural dextran.