产壳聚糖酶菌株的分离筛选及其诱变育种

Screening and mutagenesis of a chitosanase-producing strain

利用以壳聚糖为唯一碳源的选择性培养基,从自然界中筛选得到一株壳聚糖酶活较高的菌株,其壳聚糖酶活为0.59U/mL。经初步鉴定,该菌株为芽孢杆菌属,以A表示。以该芽孢杆菌为出发菌株,经硫酸二乙酯(DES)诱变处理50 min后,筛选得到壳聚糖酶活明显提高的突变株DES-4,其壳聚糖酶活为1.60U/mL,是出发菌株的2.7倍。该突变株经连续传代5次后仍稳定产酶。研究表明,突变株DES-4的壳聚糖酶产生与芽孢形成之间关系密切,当芽孢充分形成后发酵液的壳聚糖酶活力不再增大。

Using chitosan as sole carbon source, a chitosanase-producing strain was isolated from soil samples, Its chitosanase activity was 0.59 U/mL. The strain was preliminarily characterized as a Bacillus sp., designated as A. The strain A was then selected as the original strain by DES mutagenesis. After DES mutagenisis for 50 rain, a mutant （designated as DES-4） was obtained with chitosanase activity of 1.60 U/mL, which was 2.7 times of that of the original strain. The mutant was transferred for 5 times and its chitosanase activity was stable. Results indicated that there existed close relation between the chitosanase production and growth cycle of the strain DES-4. Chitosanase activity of fermented broth increased while spores began to form in the cells. Maxium chitosanase activity was corresponding to fully formation of spores.