Screening Of High-temperature Lignin-degrading Bacterial Consortium And Analysis Of Its Metabolic Pathway

Lignocellulose is the main component of straw and is the most abundant renewable resource in the world.Lignin is a component of lignocellulose with a complex structure,which seriously affects the reuse of lignocellulose.Biodegradation of lignin has attracted wide attention due to its environmental friendliness and other characteristics.Among them,the degradation of lignin by bacteria has advantages in environmental adaptability and other aspects.The purpose of this study is to obtain a group of bacterial composite consortium that can efficiently degrade lignin under high temperature conditions.Study the lignin degradation characteristics of the strain and clarify its bacterial composition.Analyze the functional microorganisms and their metabolic characteristics in the composite bacteria consortium,and provide basic research data for the utilization of cellulose in straw.In the experiment,a group of bacterial consortium LDH that can efficiently degrade lignin under high temperature conditions(50°C)was screened by restricted culture method.Use response surface methodology to optimize the lignin degradation conditions of LDH;use the method of plate streaking to isolate and identify the cultivable bacteria consortium;analyze the bacterial diversity of LDH by 16S r DNA sequence,using the metagenomic sequence method identifies functional bacteria and analyzes their metabolic characteristics,and finally determines the key bacteria in the process of lignin degradation by the bacterial consortium.The results of the study are as follows:A group of bacterial consortium with high-efficiency lignin degradation ability was named LDH.The lignin degradation rate of this bacterial consortium can reach 32.4%after cultured at50?for 10 days.The response surface method was used to obtain the degradation conditions of the optimal culture temperature,filling volume and initial p H of the culture medium,and the optimum degradation conditions were obtained as follows:culture temperature 50?,filling volume 100 m L/250 m L and initial p H 8.1 After culturing for 10 days under these conditions,the degradation rate of LDH lignin increased by 9.05%.Through the research on the degradation characteristics of the bacterial consortium LDH,it is found that the logarithmic growth phase of the growth curve of LDH lasts for 7 days,the 7th to 9th day is the stable phase,and the 9th day begins to enter the decay phase;the initial p H of the medium dropped from 8.1 to 6.58 on the third day and on the 7th day it increased to 7.51 and remained stable until the end of the culture;the laccase(Lac),manganese peroxidase(Mn P)and lignin peroxidase(Li P)enzyme activity of LDH reached the highest on the 3rd,4th and 6th day(41.11 U·L^-1,16.05 U·L^-1,15.41 U·L^-1);LDH lignin degradation rate was the first It quickly increased to 35.82%after 5 days,and then slowly increased,and the degradation rate was41.72%at the end of the culture.The purely cultured strains in the bacterial consortium were separated,and 7 purely cultured bacteria were obtained,LDH-a(Ureibacillus),LDH-b(Brevibacillus),LDH-c(Aneurinibacillus),LDH-d(Paenibacillus),LDH-e(Bacillus),LDH-g(Brevibacillus)and LDH-h(Ureibacillus).The enzyme-producing characteristics of the isolated purely cultured strains were identified,and it was found that the manganese peroxidase enzyme activity of the strains was the highest.Analysis of the microbial diversity of the bacterial consortium showed that the bacterial consortium LDH is mainly composed of Paenibacillus,Bacillus,Aneurinibacillus,Brevibacillus,etc.Among them,Bacillus(P<0.05),Anaerocolumna(P<0.05),etc.have significantly increased abundance during the peak period of lignin degradation.Based on the metagenomic sequencing data,the bacterial consortium LDH was analyzed,and the KEGG database and the EGGNOG database were used for gene annotation,and it was found that LDH can annotate the most genes for carbohydrate metabolism.According to the annotation results of the CAZy database,it is found that the enzyme families related to lignin degradation that can be annotated in the genetic composition of the bacterial consortium are AA1,AA2,AA3,AA4,AA6,AA7 and AA10.A synergistic model of the bacterial consortium LDH degradation lignin was constructed.The AA1 and AA4 families with the highest number of gene annotations participated in the degradation pathway of phenolic compounds and the metabolic pathway of non-phenolic compounds in lignin,respectively.Bacteria that can be annotated to lignin-degrading enzymes mainly include Paenibacillus,Aneurinibacillus,Brevibacillus,etc.They are the key bacteria for the degradation of lignin by the bacterial consortium,and the most important one is Paenibacillus.In summary,this study screened a group of bacterial consortium that can efficiently degrade lignin under high temperature conditions,and determined the key bacteria of the bacterial consortium through diversity and metagenomic data,and constructed the bacterial consortium lignin degradation synergistic model.Enriched lignin degradation microbial resources,and provided data support for the next step of the research and application of bacterial consortium.