Font Size: a A A

The Characteristic Degradation Of Lignin And Microbial Diversity Of Bacterial Consortium LDC

Posted on:2017-05-04Degree:MasterType:Thesis
Country:ChinaCandidate:Y LiFull Text:PDF
GTID:2180330482483479Subject:Microbiology
Abstract/Summary:PDF Full Text Request
Lignin has a complex structure which is widely present in plants biodegradable polymer organic compound.The main bottleneck utilization of lignocelluloses is the pretreatment of lignin.Single strain of lignocellulose decomposition effect no more bacterial strains of strong synergistic effect decomposition. Bacterial consortium of lignocellulose decomposition effect is far higher than that of single strain. Synergy between strains of complex microbial components and analysis of the decomposition mechanism are of great significance.This research is aimed at the lignin degradation bacterial consortium LDC.Using high-throughput sequencing technology analysis of the composition of microbial diversity.Isolated and identified the strains of LDC.The purpose of this research was to study lignin degradation characteristics,enzyme activity features, degradation micro process during degradation and degradation products of LDC.The object of the research is to provide technical parameters for the further use of the mechanism of decomposition lignin by bacterial consortium.1.Using plate marking method based on the previous experimental work 2 strains were isolated from LDC.The 2 strains were named D-7(Thauera sp.) and D-8(Pannoniber sp.).D-3,D-4, D-8 were able to degrade AL.The degradation rate were 8.5%, 4.7%, 5.6%.There were two samples named S1(LDC straw liquid cultures around) and S2(LDC after processing of the surface of the straw).There was no difference between two samples of the composition bacteria,but the species abundance of the two samples had obvious differences.S1 and S2 contained bacteria of 92 species.Relatively high percentage of the dominant species in S1 were Thauera sp.,22.32%;Pseudomonas sp.,8.80%;Proteiniphilum sp.,5.56%; Desulfomicrobium sp.,4.36%.Relatively high percentage of the dominant species in S2 were Pseudomonas sp.,26.99%;Azospirillum sp.,4.61%;Thauera sp.,3.99%.2.The best quantity of inoculation of LDC was 10%,the optimum substrate quantity was volume 2%(w/v).LDC was in the wide range of substrates and was able to adjust the pH of system.LDC degraded a large number lignin and hemicellulose of gramineous plants such as corn, rice, reed,but almost no degradation of cellulose 3 g/L concentration of AL benefit the growth of LDC even more.The lignin degradation rate and the decolorization rate was 55.18%,72.58% respectively.When the concentration of NaCl.was less than 2%, the influence of the decolorization rate of lignin degradation rate was not obvious.But they were subdued with the increase of concentration.3.LDC secreted lignin degrading enzymes including laccase, lignin peroxidase, manganese peroxidase,the largest enzyme activity, respectively,136.7 U/L,1206.5 U/L,3933.3 U/L.To get the optimum enzyme production of compound of LDC conditions the research studied and influence composite LDC lignin degradation enzyme activity of six main factors.The optimal enzyme production conditions of LDC:initial pH 8.0 medium,medium fluid volume 40%,Cu2+ 1.0mmol/L, peptone 2.5 g/L, starch 0.5 g/L, culture temperature 30 ℃.That improved enzyme activity so as the decomposition rate of lignin.4. Using SEM and GC-MS the lignin degradation of micro process and degradation products were studied with rice straw.The bacteria first destroyed the mechanical structure of the straw then removed wax layer on the surface of the straw and its siliceous structure.Then it grew with hemicellulose finally removed lignin and other components left and completed degradation of cellulose.Straw degradation products was mainly small molecules of fatty acids, aromatic acid,aromatic ester, long chain fatty acids and long chain fatty hydrocarbon.It proved that the process of Lignin degradation was lignin macromolecule polymer depolymerize to low molecular compound by way of side chain oxidation and benzene ring opening.In this experiment,the bacteria diversity of LDC was studied.The species of the 8 strains of bacteria from LDC and the lignin degradation of them were identified. The optimum initial training conditions of LDC, the characters of lignin degradation, the change rule of enzyme activity,the micro process of degradation and the degradation products of LDC was also studied.The results were good to enhance the understanding for cellulose decomposing process.
Keywords/Search Tags:bacterial consortium, lignin, biodegradation, lignin degradation enzyme, microbial diversity
PDF Full Text Request
Related items