Mutagenic Method And Enzyme Properties Investigation Of Xylanse Producted By Aspergillus Niger

Hemicellulose in the fiber composition of plants,accounting for about20%to30%,hemicellulose is the second most abundant renewable resources which following cellulose,Xylan is an important component of the hemicellulose. Xylanase is a composite class of enzymes belong to hydrolases,Degradation of xylan into xylose or oligomeric xylan,including a variety of exonuclease and endonuclease. At present,the degradation of xylan,Mutation breeding of strain which can produce the xylanase and to improve and maintain the enzyme activity is the main object of study. In this study,the starting strain Aspergillus AS3.350,using UV,fast neutron,diethyl sulfate,nitrosoguanidine,sodium sulfite,five mutagen to mutagenic,Filter out the high-yield strains which produce xylanase,to optimize the culture conditions,and study the enzymatic properties.the results are as follows:1.UV irradiation:set at256nm wavelength,the vertical distance is20cm,exposure time is90s,obtained mutant UV256-90-1the activity is133.21U/ml,it is1.7times of the original strain.2.Fast neutron irradiation:dose rate0.0025Gy/s and vertical distance12cm,the optimal dose is0.75Gy, screened out the mutant Fn5-2,the activity is134.77U/ml,it s1.72times of the original strain.3. Diethyl sulfate mutagenesis:DES/bacterial suspension the volume ratio is1:250,mutagenic time20min,screened out mutant enzyme activity is118.31U/ml,it is1.51times of the original strain.4. Nitrosoguanidine mutagenesis:the MNNG concentration0.5%,the mutagenic time20min,screened out the mutant activity is108.12U/ml,it is1.38times of the original strain.5. Sodium nitrite mutagenesis:sodium nitrite concentration is0.1%,mutagenic time20min,screened out mutant highest activity is114.39U/ml,it is1.46times of original strain.6. The fast and DES combined mutagenesis:Select the DES with the bacterial suspension volume ratio is1:250combined mutagenesis the mutant Fn5-2and screening to FnD5-2activity reached the157.07U/ml,improve2times than the original strain.7. Conduct the nitrogen source alternative,use cheap soy protein instead yeast extract,to optimize the right FnD5-2culture conditions,obtain the optimum culture conditions is28℃,pH5.0,add the amount of Tween80is1.5ml,the addition of nitrogen is4g,amount of medium is50ml.8. Enzymatic properties of xylanase produced by Aspergillus niger FnD5-2,get the following results:the optimum temperature is50℃; optimum pH is5.0;4℃～50℃and pH4～6Stability is better; Mg2+、Fe2+、 K+、Ca2+had activation function, Mg2+had the most significant of activation function; Zn2+、Fe3+、Ba2+the effect is not very obvious; Co2+、Cu2+、Na+、Mn2+had inhibitory action, Mn2+had the most obvious of the inhibition.