Screening Of Mutant Strains With Highly Producing Acid Cellulase And Its Enzymic Properties

Using N⁺ ion-implantation, He-Ne laser and Co⁶⁰γ radiation respectively,experiments were conducted on Penicillium decumbens A10 to compare the mutants' cellulase-producing ability.The results show that Co⁶⁰γ radiation is the best of three means which best mutant dosage is 550Gy.A mutant with high cellulase activity was screened, naming A50.The cellulase activity of the mutant kept stable after 8 generations.After orthogonal designing experiment, the optimum fermentation conditions of A50 were obtained, which is as followed:the major carbon resource is 5%,the ratio between wheat bran and corn straw is 5:5, the concentration of glucose as supplemental carbon is 0.1%,the concentration of (NH₄)₂HPO₄ as supplemental nitrogen resource is 0.2%,the initial pH of liquid medium is 5.0,the inoculum size is 10% and the concentration of Tuwen-80 is 0.1%,30ml media were filled in the 300ml flask with culture temperature 32℃, 200rpm.Under the optimum conditions,the highest enzyme activities of CMC and filter paper is 27.28U/ml and 1.98U/ml respectively to 60h which are 33.2% and 45.59% respectively higher than the initial strain.The SDS-PAGE revealed the culture supernatant of the initial strain and the mutant contained different protein bands, which exactly demonstrated at protein level that A50 was surely a mutant of A10.CMCA and FPA of the mutant have their optimum activities at pH4.0 and pH5.2 respectively.They have better stability in the range pH 4.0～6.0 when incubated at various pHs at 40℃ for 2hrs. The CMCA has maximal activity at 45℃ and the enzyme'optimum FPA is at 60℃.They have better stability up to 45℃ when incubated at various temperatures for 1h. Their temperatures for loss half activity in 1h are 50-55℃ or so。...