青霉的纤维素酶抗降解物阻遏突变株的选育

从土样中筛出一株生长快,产纤维素酶较高的斜卧青霉(Penicillium decumbens114-2)。能在全纤维素(hlocellulose)双层平板上形成清晰的透明圈。摇瓶培养的滤纸酶活可达8.8mg 葡萄糖/ml.h。 114-2菌株(其纤维素酶合成可为葡萄糖所阻遏)经UV和NG诱变处理后,在含葡萄糖的全纤维素平板上筛选到多株仍能形成明显透明圈的突变株。其中JN15和JU1在含葡萄糖的全纤维素液体培养基中,在残余葡萄糖浓度为 1％左右时,滤纸酶活可分别达到7.3 和13.9mg葡萄糖ml·h。这是出发株114-2和纤维素酶高产菌株木霉EA_3-867和QM9414所不能的。在不加阻遏剂的对比试验中,两个突变株的纤维素酶产量都比较高。其中,JU1的滤纸、CMC和棉花酶活分别达到33mg葡萄糖/ml·h,234mg葡萄糖/ml·h和86mg葡萄糖/ml·24h。

SCREENING OF CATABOLITE REPRESSION-RESISTANT MUTANTS OF CELLULASE PRODUC1NG PENICILLIUM SPP

A screening method of double layer agar plate was improved by using holocellulose instead of acid-swollen cellulose as substrate. Using this method, a high cellulase producing fungus Penicillium decumbens 114-2 was isolated from the soil. The strain 114-2 was continually mutated with UV and NG. A series of catabolite- derepression mutants were selected on the holocellulose plate in the presence of excessive glucose. These mutants can hydrolyze holocellulose in the plate, but neither the parent strain 114-2 nor two of the high cellulase producing mutants (Trichoderma EA_3-867 and QM9414) have tais ability. Among the non-repressible cellulase producing mutants, two strains, JN15 and JU1, clearly produced a great amount of cellulase in the liquid holocel- lulose-glucose medium. In addition, when JU1 was grown on a medium containing holocellulose as the sole carbon source, the sasccharifying cellulase activities of JU1 on filter paper, CMC and cotton were as high as 33 mg glucose/ml. h, 234 mg glucose/ml.h and 86 mg glucose/ml.24h respectively. The cellulase production of P. decumbens strains, especially in JU1, is more sensi- tive to low pH. Thus, the addition of CaCO_3 is favorable.