Screening Of A Microbial Consortium For Selective Degradation Of Lignin And A Study Of Its Degradation Of Green Waste

Green waste that is comprised by substantial lignocellulose,can serve as a kind of important biomass resource,whose efficient use tends to relieve the energy shortages.Associated with lignin through a network of covalent bonds in green waste,the hemicellulose is effectively protected,where its employ nonetheless is greatly hampered.Aiming in analysing the selective lignin degradation of a microbial consortium,this study screened microbial consortia with a selective function in lignin degradation that were sampled from rotten trunks,rotten stumps and soil near it.Furthermore,the lignocellulose degradation performance of different strains was studied on a basis of treatment results,after applying the microbial consortium in degrading green waste.To acquire microbial consortia DT-1,DT-2,DM-1and DM-2 that are effectively capable in lignin degradation,samples obtained from rotten trunks,rotten stumps and soil near it in the arboretum of the South China Agricultural University were screened before the consortia were isolated throughgenerations of subculture.As repeatedly inoculated for a5^th time,pH value of four groups of microbial consortiaremained between 7.5 and 8.0 in the end.Thus,it could be concluded that these microbial consortia exhibited a steady growth state in re-screeningmediums.DM-1,the desired one,whose degradation percentage up to28.37%,also has the highest selectivity of lignin degradation that was manifested by its highest SV?2.78?within 16days'cultivation.Meanwhile,aremarkable reduction in the fiber crystallinity of green waste?10.35%?resulted from the bio-degradation ofDM-1,displayed a greater exposure of cellulose by selective lignin removal.Four groups of microbial consortia?DT-1,DT-2,DM-1,DM-2?were inoculated into three kinds of new mediums based on alkali lignin,filter paper and acid-treated woodchipsto explore the effects of different carbon sources on the degradation of lignocellulose by the microbial consortia.Besides,all of them could grow well in basic medium of different carbon sources.Amongst,DM-1 shown the steadiest growth in alkali lignin medium.The degradation rate about DM-1 of acid-treated woodchipsalkali lignin and filter paper were 49.50%and 24.18%,respectively.Meanwhile,it had the highest SV?2.05?indicating its optimal performance in degradation of alkali lignin and filter paper,was significantly higher than the other 3 groups?p<0.05?.The microbial consortium DM-1had a superior degradation rate of acid-treated woodchips?33.46%?as well.In varying growth periods of these three culture mediums,the ligninase activity of DM-1 performed stably,whose value was distinctly higher than the value of its cellulase activity.It pointed out that the selectivity of microbial consortium DM-1 in lignin degradation is independent of altering carbon sources.Microbial component diversity of the microbial consortium DM-1 was identified by combined the PCR amplification technique and the 16S rDNA sequencing in the region between V3 and V4.Observed species value,chao value,ace value and OTU number are 7,which shown a high complexity in this sample.The result revealed that DM-1 was comprised by five genera:mesorhizobium,cellulosimicrobium,pandoraea,achromobacter and stenotrophomones.The stenotrophomones accounted for more than 92%of DM-1 that is the predominant genus.Specific composition of microbial consortium DM-1 was analysed by using plate isolation and gene sequencing.A total of 12 monobacillus strains were isolated from DM-1 by using traditional pure culture technology,involved 3 strains of fungi,4 strains of bacteria and 5 actinomycetes.The effects of DT-1(TT_DT),DM-1(TT_DM),pleurotus ostreatus(TT_PO)and agaric (TT_AF)on lignocellulose degradation were also evaluated on a basis of bag culture was also evaluated.The results showed that 4 different strains could grow normally in the bacteria bag,and within 15 days,the mycelium could be full of bacteria bags.Amongst,the degraded lignin in green wastes of TT_DT and TT_DM were respectively 10.99%and 10.24%,which were higher than the ones of TT_PO and TT_AF.TT_DMM was highlighted by a distinct degradation percentage?24.10%?,which was significantly higher than TT_PO and TT_AFF groups?p<0.05?.Although the selective performance of DM-of degrading the lignin in green wastes was weaker than that of shaker in the solid culture of bacteria bag,the surface structure of lignocellulose in the green waste wasseriously damaged after the treatment of DM-1 whilethe cellulose area exposed to cellulase was increased?SEM?,which could contribute to further reuse of the cellulose.