The Yield And Function Of New Enzymes Depend On Corn Husk

Corn husk is a by-product about wet preparation of corn starch,which is mainly used as fiber feed.However,due to the high content of hemicellulose,low digestibility and utilization rate,it will also produce anti nutritional effect,which limits its addition in feed.Therefore,it is urgent to explore the efficient utilization of corn husk.Corn husk is rich in xylan,arabinoxylan,ferulic acid and other components.Through enzymatic hydrolysis,on the one hand,it improves the digestion and utilization rate of corn husk and increase its nutritional value and addition as fiber feed.On the other hand,it produces high-value products such as xylooligosaccharide,L-arabinose and ferulic acid,which is important to realize the efficient utilization of corn husk.Efficient and specific enzyme preparations’ creation is the key.Aspergillus niger is a filamentous fungus used in food industry,which has high safety.And it secretes a variety of cellulase and hemicellulase,which is an ideal system for efficient expression of food grade cellulase and hemicellulase.This project is based on the food grade Aspergillus niger expression system established in the early stage of the laboratory.The purpose is to obtain the recombinant strain of high-yield hemicellulase enzyme system and provide enzyme preparation strain resources for the efficient enzymatic utilization of corn husk.The main research results are as follows:(1)Through homologous recombination technology,Agrobacterium mediated method transformed Aspergillus niger successfully,and five homozygous recombinant strains were obtained α-L-arabinofuranase high-yielding strain TH-2(gla A::abf A),xylanase high-yielding strain TH-2(gla A::egl C),ferulate enzyme high-yielding strain TH-2(gla A::fae A),xylanase high-yielding strain TH-2(gla A::xln A),xylanase high-yielding strain TH-2(gla A::xyn B).The highest enzyme activities were 595.89 U/m L,913.56 U/m L,274.24 U/m L,792.16 U/m L and1918.63 U/m L respectively.(2)Five enzymes depend on 20 ～ 80℃ and p H 3 Relative enzyme activity between 5 and 9.5.α-The optimum temperature of L-arabinofuranase(Abf A),xyloglucanase(Egl C),ferulate esterase(Fae A),xylanase(xln A)and xylanase(Xyn B)was 50℃,and the relative enzyme activities were123.8%,134.7%,109.2%,112.7% and 124.0% respectively.However,the optimum p H of these five enzymes is different.among α-The optimum p H of L-arabinofuranosidase(Abf A)was 7.5and the relative enzyme activity reached 113.1%.Xylanase(Egl C),xylanase(Xln A)and xylanase(Xyn B)reached the highest relative enzyme activity of 100% at p H 5.5.The relative activity of ferulate esterase(Fae A)was 100% at p H 6.5.(3)The content of ferulic acid in the hydrolysate of corn bran increased significantly after the treatment of corn bran with Fae A,which proved that Fae A could effectively hydrolyze the ferulate bond in corn bran.After Egl C,Xln A and Xyn B were used to treat the wood in corn husk,the content of xylooligosaccharide in corn husk hydrolysate increased significantly,which proved tha t Egl C,Xln A and Xyn B could effectively hydrolyze xylan or xylan in corn husk.After the corn husk was treated with Abf A,the increase of arabinose content in corn husk was not obvious,indicating that Abf A had no function of hydrolyzing arabinofuran glycoside bond.