Mutation Of The Strain Highly Producing Acid Xylanase And Its Enzymic Properties

The spores of A. niger M1, the initial strain, was treated by U.V. at morality of 90% . A mutant with high xylanase activity was screened ,naming A. niger J 506. The xylanase activity of the mutant kept stable after 10 generations.After orthogonal designing experiment, the optimum fermentation conditions of A. niger J 506 were obtained, which is as followed: concentration of the major carbon resource 4 %, ratio between bran and corncob 5:5, concentration of glucose 0.1%, concentration of ammonium oxalate as supplemental nitrogen resource 2.0%, the initial pH of liquid medium 5.0, 100ml/250ml flask.The PAGE revealed the culture supernatant of the initial strain and the mutant contained different protein bands, which exactly demonstrated at protein level that A. niger J 506 was surely a mutant of A. niger M1. Zymogram stained with xylan-Remazol brilliant blue for detecting xylanase showed there are three different xylanases in the mutant culture, while two xylanases in initial strain. What is important, the third xylanase in A. niger J 506 have higher activity and more production levels from PAGE and zymogram of xylanase.Xylanases of the initial strain and the mutant have their optimum activity at pH 5.4 and pH 6.0 , respectively. They have better stability in the range pH 7.0-10.0 when incubated at various pHs at 45℃ for 2 hr. The two xylanases have maximal activity at 52℃ and have better stability up to 50℃ when incubated at various temperatures in pH 6.0 for 30min. Their temperatures for loss half activity in 30mm are 55℃ or so.