Screening And Characterization Of Cellulose Degrading Bacteria

Cellulose is the most abundant and widely distributed organic substance in nature,and it is an important renewable resource on Earth.Jilin Province has rich cellulose resources,but most of them are burned or abandoned,causing serious environmental pollution.The key to converting cellulose into small molecular compounds or other nutrients is to screen and isolate excellent bacteria capable of degrading cellulose.This paper focuses on the screening of cellulose-degrading bacteria,optimization of enzyme production conditions,enzymatic properties,and preliminary study of the cellulase-degrading bacterial genome.The main research content and results are as follows:(1)Screening of cellulose-degrading bacteriaUsing carboxymethyl cellulose sodium as the sole carbon source in the culture medium,combined with Congo red staining,filter paper decomposition experiments,and cellulase activity determination,ten strains of cellulose-degrading bacteria were screened from sheep,deer excrement and surrounding soil.Among them,strain YS showed the best degradation effect,with CMCase and FPase activities of 50.80 U/m L and 31.62 U/m L,respectively.Through colony morphology,physiological and biochemical identification,and 16 S r DNA molecular biology technology,it was preliminarily identified as Bacillus cereus.(2)Study of enzymatic propertiesThe optimal temperature for enzyme production of strain YS was 30℃,the optimal pH was 7.0,the optimal time was 60 hours,and the optimal inoculum size was 6%.The best carbon source was beef extract,followed by peptone.Mg2+,K+,and Na+ ions promoted the relative enzymatic activity of strain YS towards cellulose,while Zn2+,trivalent Fe3+ ions,and Cu2+ ions had inhibitory effects.(3)FTIR and SEM analysis of functional group changes and GCMS product detectionThe corn stalks degraded by strain YS showed a sponge-like structure and were more aggregated under SEM.FTIR analysis showed that the aromatic skeleton carbon of lignin was destroyed,and the carbonyl or aldehyde groups and the non-conjugated carbon peak were significantly weakened,indicating that strain YS can break down the structure of lignin.The peak of carbohydrates was significantly weakened,indicating that strain YS can degrade hemicellulose in corn stalks.GCMS analysis showed significant changes in the types or contents of metabolic products produced after seven days of co-culture of corn stalks and strain YS.(4)Preliminary analysis of the whole genomeThe ONT sequencing platform was used for sequencing,and the YS genome size was5887191 bp with a total of 17831 base pairs.A total of 5760 protein coding genes were predicted in the genome,among which 4038 genes were annotated in the egg NOG database,4401 genes in the GO database,2526 genes in the kegg database,and 5736 genes in the nr database.There were 182 carbohydrate protein coding genes,including 41 GH family genes.The Cazy annotation results showed that there were 11 genes encoding cellulases.