Mechanism Of Corn Stover Degradation By White Rot Fungi Treatment And Application In Production

Corn stover is an attractive renewable resource for the production of ruminant feeds,however,ligninnocellulose in the cell walls restrict the effective utilization of the stover by rumen microbes.White rot fungi treatment has been regarded as an effective method to improve the digestibility of lignocelluloses biomass.The objective of this study is to screen the most effective white rot fungi that can efficient degrade the ligninnocellulose of the corn stover,to elucidate the ligninnocellulose degradation mechanism of the selected fungi,to study the effect of mixture fungal treatment on the degradation of the corn stover,and to develop a method to treat corn stover under non-sterile conditions.The main designs and results are as follows:1.A total of seven fungi were evaluated according to their growth rates and selective values on two kinds of different acid detergent lignin(ADL)content of corn stover held under 28 ? for 28 days.Then,the stover treated with three selected fungi were evaluated by their in vitro gas production(IVGP).The results showed that Irpex lacteus,Pleurotus ostreatus,and Pleurotus cystidiosus had high speeds of colonization,and high selective values on both stover.However,the IVGP of the low ADL content of corn stover treated with any of the three fungi was lower than that of the raw stover(P<0.05).There was no significant change of the IVGP of the high ADL content of corn stover treated with P.ostreatus and P.cystidiosus(P>0.05),however,the IVGP of the stover treated with I.lacteus significantly increased from 199 mL/g organic matter(OM)to 266 mL/g OM(P<0.05).2.The effect of prolonged treatment time of 42 days and 60 days incubation with I.lacteus,P.ostreatus and P.cystidiosus on the chemical composition of the high ADL content of corn stover were investigated in this study.Changes in the IVGP,lignocellulolytic enzyme activity,and multi-scale structure of the corn stover were analysed.The result indicated that prolonged the treatment time by P.cystidiosus cannot improve the IVGP of the stover(P>0.05),however,the IVGP increased significantly after the I.lacteus and P.ostreatus treatment for 42 days(P<0.05).Moreover,the cellulase activity was highest at the later stage of I.lacteus treatment of the stover.Multi-scale structural analysis indicated that.lacteus increased and enlarged substrate porosity,degraded and modified the amorphous area of the stover,and decreased the strong of bond relate with lignin.3.The effect of the different inoculation size of I.lacteus on the fungus growth speed and the degradation characteristic of the corn stover were evaluated in this study.And the effect of I.lacteus and Aspergillus oryzae var.effuses combination on the degradation rate of corn stover was studied.The result indicated that inoculation size of 4%of wheat grains covered with mycelium of I.lacteus can effective and economic degraded the corn stover.Increased the particle size of the corn stover can further increased the lignocellulose degradation rate and crude protein content treated with the I.lacteus but cannot further increased the IVGP.Simultaneous inoculation of two fungi treatment of the stover for 28 days can further increased the degradation rate of lignocellulose in the corn stover.4.The abilities of I.lacteus to colonize and degrade ligninocellulose in ensiled corn stover with lactic acid bacteria(LAB)inoculation was investigated under non-sterile conditions.Results revealed that LAB could improve the silage quality of the corn stover,and the corn stover silage inoculated with L.planturam produces more lactic acid and higher IVGP than other groups;Irpex lacteus colonies flourished on the stover during the early stage of silage,especially on the 3-day corn stover silage inoculated with mixed strains of L.buchneri and L.planturam.This led to an 18%decrease in the acid detergent lignin(ADL),and a 49.6%increase of the IVGP compared with the raw stover.In addition,after I.lacteus treatment of the corn stover pretreatment with the mixed LAB silage,I.lacteus accounted for 99.5%of the total fungi.However,there was only 9.5%of I.lacteus in the CK silage group which had not been pretreated with LAB.Compared with the silage pretreated with LAB,the higher abundance of the fungi in the CK silage group was mainly Monascus,the higher abundance of bacterials were mainly Nonomuraea and Glycomyces,combined with the growth and abundance of I.lacteus in the CK group,therefore,it suggested that these typies of microorganisms have a great effect on the growth of I.lacteus.