Breeding Of High-yield Xylanase Producing Strain And Preparation Of Pharmaceutical Microcrystalline Cellulose By Enzymatic Method

In this paper,the Aspergillus niger FXY was first screened from the soil,and the xylanase-producing bacteria P-UV-17 was obtained by ultraviolet,atmospheric and room temperature plasma?ARTP?and combined mutagenesis of the two.In order to further improve the enzyme activity of the xylanase produced by the strain,the fermentation conditions and fermentation medium formulation were optimized,and the enzymatic properties of the xylanase produced were studied.Finally,the medicinal microcrystalline cellulose?MCC?was successfully prepared by using the xylanase produced by the strain.The specific conclusions are as follows:?1?The optimal conditions for UV mutagenesis were:strain culture for 4 d and UV irradiation for 6 min;the optimal conditions for ARTP mutagenesis were:strain culture for 4 d and ARTP irradiation for 5 min.Then,the complex mutagenesis was carried out under the optimal conditions.Finally,the dominant strain P-UV-17 which was stably inherited by ARTP-ultraviolet mutagenesis was screened,and the xylanase activity was202.51 U/mL.Compared with the starting strain FXY,it increased by 154.99%.Through research,it is concluded that the increase in the enzyme activity of the xylanase produced by the dominant strain is not due to the increase of the biomass of the strain,but to the increase of the specific activity of the enzyme.?2?The optimal fermentation conditions for strain P-UV-17 were obtained by single factor experiment:fermentation time was 96 h,fermentation temperature was32?,initial pH of the medium was 6.0,inoculum was 4%,and shake flask?250 mL?volume is 50 mL and the shaker speed is 180 r/min.The optimal components of the fermentation medium were obtained by response surface optimization:bran 17.47 g/L,glucose 9.78 g/L,yeast powder 5.73 g/L,potassium dihydrogen phosphate 1.00 g/L,and magnesium sulfate 0.80 g/L.The xylanase produced by the strain has an optimum temperature of 45?and an optimum pH of 7.0,and the stability of the enzyme is good at this temperature and pH.?3?On the basis of SO₃ micro-thermal explosion combined with dilute alkali treatment,treatment of crude hemicellulose with xylanase can not only improve the whiteness of the sample,but also reduce the amount of NaClO₂ by 75.50%.The MCC prepared by enzymatic method basically conforms to the pharmacopoeia standard,indicating that enzymatic preparation of medicinal MCC is a feasible green process.