Study On Enzyme Production Characteristics Of Aspergillus Niger HQYX And Its Application As Feed Additive For Fermentation Of Cotton Straw

Xinjiang is the main cotton producing area,where cotton straw is rich in biomass.It has the basic nutrients needed by ruminants.However,higher lignocellulose content has always been an important limiting factor for the feed conversion of cotton straw.At present,the degradation of lignocellulose by fungal fermentation of cotton straw is mostly used in organic substrates.Therefore,through breeding the cellulose-degrading bacteria Aspergillus Niger which can be added to feed,the shaking flask and solid-state fermentation technology were optimized,and the mechanism of Aspergillus Niger in cotton straw solid-state fermentation was preliminarily explored,which laid a good theoretical foundation for the application of fungi to ferment cotton straw feed.The main results are as follows:1.Six strains of Aspergillus niger were screened with Congo red carboxymethyl cellulose sodium medium.The disintegration test of filter paper and the determination of enzyme activity were re-screened.The results showed that Aspergillus Niger HQYX produced the largest transparent ring,the best degradation effect of filter paper and the highest relative enzyme activity.2.Firstly,the flask fermentation conditions of Aspergillus niger HQYX were optimized by single factor test and double index response surface method to determine the optimal fermentation conditions:starch concentration 1.20 g/100 mL,peptone mass concentration 0.25 g/100 mL,phosphoric acid dipotassium 0.10 g/100mL,culture time168 h,rotation speed 170 r/min and inoculum size 8%,carboxymethyl cellulose activity?CMC enzyme activity?435.44 U.mL-1,filter paper enzyme activity?FPA enzyme activity?183.66 U.mL-1.The bacterial liquid under optimal fermentation conditions was connected,and the cotton stalk was the sole carbon source.After 30 days of fermentation,the cellulose and hemicellulose content of cotton stalk decreased from40.5%,11.9%to 30.6%,7.7.%,the highest degradation rate of cellulose was 24.44%,and the highest degradation rate of hemicellulose was 35.54%.3.The optimal fermentation conditions were determined by the Box-behnken combination design,and the mass ratio of cotton straw to corn flour was determined by optimally selecting the bacterial liquid under the fermentation conditions of the shake flask and the solid fermentation medium with cotton stalk as the carbon source 5:1,inoculum 8%,water content 65%,fermentation 60 days,enzyme activity 310.885U.mL-1;determination of the lignocellulose degrading enzyme system of Aspergillus niger,which produced higher xylanase?2803.33 U.mL-1?,carboxymethylcellulose sodium enzyme?282.01 U.mL-1?,filter paper enzyme?462.63 U.mL-1?and laccase?81.94 U.mL-1?,lower Manganese peroxidase?16.84 U.mL-1?and lignin oxidase?about 0.50¹.00 U.mL-1?were used to determine cotton stalk composition.The cellulose and hemicellulose were from 40.10%to 28.50%,11.76 to 7.90%,and lignin from 15.59%to 11.58%;the degradation rate of cellulose,hemicellulose and lignin reached a maximum of 28.50%,32.89 and 25.68%on days 60,40 and 60,respectively.4.Cotton straw was fermented with compound bacterium agent by stages.From sensory evaluation,most of the test groups were rated as excellent feed,while the control group was inferior feed.The pH value of the control group was the highest,significantly higher than that of other test groups,and the pH value of the test group 13?Aspergillus Niger+Lactobacillus casei+Bacillus licheniformis?was the lowest?3.68?.The dry matter content of the test group 13 was 27.01%,the crude protein content was26.0%,and the gossypol content was reduced to 16.4 mg.kg^-1.