Screening And Identification Of The Lignin-degrading Fungus On Corn Stalk And The Study On The Fermentation

With the rapid economical development, the energy demandof our country isgrowing with each passing day. Owing to the growing shortage of coal, oil and othernon-renewable resources, non-grain feed production of cellulosic ethanol which isrenewable energy have been paying attention.Corn straw is rich sources of fiber andbe used to produce cellulosic ethanol. This trendhas been in development. The processof using straw to produce ethanol has great development, however,manyproblemshavebeen not solvedso far, such as the low efficiency of the pretreatment, the low activityof the cellulaseand the low efficiency on saccharification efficiency. In order to solvethe low effective of corn stover pretreatment, this studyis aimed atisolatinga strainwhich can degrade efficiently corn stover lignin, optimizingits fermentationconditions ofenzyme production, fordegradating efficiently ligninand releasingofstraw cellulose and hemicellulose components as much as possible,improvingtheefficienc of saccharification and resources and providinga basis for industrialproduction. The main contents are as follows:At first,262colonies were isolated from the soil ofreturning field of corn strawcorn for many years. By the colorful reactions of PDA-Guaiacol plates and thedecolorizations of PDA-Aniline bule plates motheds,5strains wereobtainedpreliminary had high production oflaccase and peroxidase.And then, amongthese strains,strain LYADJ-1has the highest enzyme activityand could produce threelignin enzymessimultaneously. Based on these results of colony morphology andsequencing analysis of ITS gene thisstrain belongs to Phanerochaete chrysosporium,and it was namedPhanerochaete chrysosporium LYADJ-1. Thisstrain was furtherresearch.A mutant strain LYADJ-1-09was obtained and hada higher enzyme activitybyUV mutagenesis. The mutant strain wascultured in a liquid enzyme productionmedium of the ninth day, and the enzyme activity reached a maximum is4600U/L.Compared with the wildstrain, the enzyme activity of mutant strainimproved1.5times.Secondly, the studies of the liquid fermentation conditions of mutant strainLYADJ-1-09for enzyme production were carried out by the single factor andorthogonal experiments.Theresults, of the optimal fermentation conditions were asfollows: the glucose concentration10g/L, the ammonium tartrate concentration is0.9g/L,Twain-800.1g/L, the fermentation temperature35°C, substrate pH4.5, incubation time6days.Under these conditions, the Lip activity was the highestandreached to6229U/L,and it reached the unoptimized1.35times.In addition,theresult of orthogonal experiment demonstrated that during the whole incubation, theglucose content is the most influential factor of the lignin peroxidase activity,followed the incubation temperature and initial pH, other factors have less impact onenzyme activity.Finally, the study of the corn stover lignin degradation was accomplishbyusingthe crude enzyme obtained under the optimize conditions culture.The optimalconditions of degradation of lignin were ascertained by single factor analysis andorthogonal test: the adding amount of the enzyme solution50mL,enzyme hydrolysistemperature45°C,the initial pH value4.3, the degradation time60hours.In thiscondition, the rate of lignin degradation can be as high as29.76%. Analysis resultsrevealed that during the enzyme solution of lignin degradation process, the addedamount of the enzyme solution wasthe most important factors to affect the rate oflignin degradation followed the initial pH and the degradation temperature oforthogonal experiment. Experimental data provide a basis for further industrialresearch.