The Breeding Of Xylanase Production Strain And Study On It’s Culture Conditions

Xylan is the main components of hemicellulose, it is one of the most abundantregenerated resources in the natural world. As the key enzyme in the xylan degradation，xylanase could converse wood fiber materials into fuel and solvent and other usefulmaterials. Also xylanase is used widely in the food，papermaking industry. So itsdevelopment potential is extremely huge for the breeding of high xylanase-producing strain.In this paper，a xylanase produced strains is screened out from nature with xylan asthe sole carbon source. After separation and purification， the UV-induced andmicrowave-irradiated composite mutagenesis is conducted on the strains.Then thehigh-yield xylanase strain C3and C5can be obtained，whoses enzyme activity are1132U/ml and982U/ml. After several passages，strain C5’s genetic character remained stablebut strain C3was not.For the hereditary features of the strain C3appear instable，so we conduct cytomixisbetween the strain C3and the Penicillium P5kept in our department. After protoplastfusion a strain R10with high enzyme activity and stable hereditary features is screenedout，whose enzyme activity reaches1348U/ml. Then18sRNA bacterial strain identificationis made to find out that the bacterial strain is Penicillium citrinum strain R10.Via the experiment design procedures of response surface，optimize the liquidfermentation conditions of the R10strain,determine the optimal medium composition iswith2.5%bran，2.5%corn flour，0.2%（NH₄）₂SO₄，0.5%KH₂PO₄，0.1%MgSO₄·7H₂O，100ml distilled water，natural pH，triangular flask of50ml/250ml，spore inoculation onslope，28°C，200rpm，and6-day shaking flask fermentation. After optimizing，the enzymeactivity can reach1653U/ml at the top. It improved22.7%before optimal. Studies on theenzymology properties of penicillium citrinum strain R10indicate that its optimumtemperature is45°C，and its enzyme activity will decrease gradually under the conditionsbelow40°C or above50°C. It’s optimum pH is5.5，and stability ranges from5.0to6.0.