Isolation,Identification And Degradation Of Corn Straw By Xylaria Sp.L1.

Corn straw is one of the most abundant agricultural residues and is considered to be the main renewable energy source.However,the straw can not be used effectively and there is still a large amount of waste.Therefore,it is necessary to promote the bioconversion of corn straw biomass.Due to the hard surface of straw and the complex structure of lignocellulosic material,it is very important to pretreat straw before fermentation.The termite nests are microenvironments rich in bacterial and fungal communities,which are high quality bio-resources to isolate high quality strains.Here,we got a fungus from an abandoned termite nest.Further,the ability of the strain degrading lignocellulose of corn straw was detected and the functional genes involved in lignocellulose degradation were explored by RNA-seq sequencing.The main results are as follows:(1)A large fungus was successfully isolated from the fruiting bodies collected from the abandoned termite nests in the wild.Through morphological identification,microscopic examination,scanning electron microscope observation and ITS identification,this strain showed highest homology(99%)with Xylaria.Then,The strain was named as Xylaria sp.L1.De Novo sequencing results showed that the genome size of this strain was 36.61 Mb.Genomic functional annotation results showed that the genome contained a high proportion of carbohydrate metabolism genes,including a variety of enzymes related to lignocellulosic degradation genes.(2)The strain was degraded by solid fermentation using straw as substrate.After 12 days of treatment,the biomass loss of corn stalk was 31.49%,the degradation rate of hemicellulose was up to 40.3%,and the degradation rate of lignin was 20.9%,the degradation effect was obvious.Scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR)and X-ray diffraction(XRD)were used to characterize the degradation effect of Xylaria sp.L1.It was found that the surface structure of the fermented corn stalk was damaged,with obvious pore diameter and increased crystallinity,indicating that Xylaria sp.L1 could effectively degrade corn straw.At the same time,the secondary metabolite extracellular polysaccharides produced in the fermentation process were further studied.The polysaccharides obtained were mainly composed by mannose(6.80%),ribose(3.34%),glucuronic acid(40.99%),galacturonic acid(0.91%),glucose(38.59%)and fucose(9.31%).Furthermore,extracellular polysaccharide had strong scavenging ability for DPPH free radical,superoxide and hydroxyl free radical.(3)A total of 1151 significantly differentially expressed genes were identified by RNA-seq.Of which,601 differentially expressed genes were up-regulated and 550 differentially expressed genes were down-regulated.GO and KEGG results showed that genes were enriched in carbohydrate metabolism.Aromatic compound decomposition process,REDOX process,etc.These pathways are directly or indirectly involved in the degradation of biomass.Combined RNA-seq and enrichment analysis,CHU98＿G5402,CHU98＿G8787,ANO14919＿057050 and V-type proton ATPase 16 k Da Proteolipid were finally determined Ano14919＿090670,EKO27＿G10375,CHU98＿G577,Ano14919＿054670,Putative 3-oxoacyl-acyl carrier protein The reductase,CHU98＿G10939,ANO14919＿033240 and ANO14919＿025600 were verified to be candidate genes affecting lignocellulosic degradation of corn straw,the results showed that Xylaria sp.L1 is a strain with good degradation ability to corn straw,which is expected to be used in the development and utilization of biomass resources such as waste straw.