Screening And Identification Of Phenol Degradation Strain In Cold Regions Of The North

The purpose of this experiment is to explore the possibility of the presence of typical phenol-degrading strains.Screening and identification of phenol-degrading strains and optimizing the environmental influencing factors of the selected strains for phenol degradation in the northern cold region of China were studied.The study could provide theoretical basis and data for biological treatment of phenol-containing wastewater.Soil,water and sediment were used as sources of strains in chemical plants,power plants and polluted areas of domestic wastewater.Microorganisms from a typical phenol polluted environment with phenol medium were isolated and cultured.Resistant strains to phenol were repeatedly acclimated under phenol concentration of 500 mg·L^-1,700 mg·L^-1,900 mg·L^-1 and1100 mg·L^-1,so that the phenol efficient degradation strains in the northern cold region of China were screened out effective biodegrading resistant strain to phenol.The sequence of 16 S r RNA gene was sequenced.The sequence of gene was searched through Blast to determine the phylogenetic status of the gene,and the phylogenetic tree was constructed.Combined with bacterial morphology,contact enzyme test,oxidase test,glucose oxidation and fermentation test,lactose fermentation test,starch hydrolysis test,methyl red test,strontium base test,H₂S test,citrate use test and other physiological and biochemical experiments,strains screened out were identified.Based on the results of single-factor experiments of the inoculation amount of bacteria,initial phenol content,shake flask volume,and temperature,and the application of Design-Expert software 10.0.7 Box-Behnken experimental design response surface method,the phenol degrading conditions were optimized to obtain the optimal environmental conditions.Ten resistant strains to phenol were obtained from samples collected from a typical phenol-contaminated environment.Among them,there were 5 strains with phenol degradation ability and 1 strain with better phenol degradation that was a Gram positive small rod-shaped spores bacteria and was sensitive to gentamicin and erythromycin.By sequencing the 16S rRNA gene and comparating Genbank,the strain was identified as Bacillus Thuringiensis.By investigation the environmental factors affecting phenol degradation such as the inoculation amount of bacteria,shake flask,phenol initial addition and temperature,the response surface method was used to optimize the environmental factors of phenol degradation,and the regression equations of the four factors on the degradation rate of phenol were calculated.The optimal environmental conditions for phenol degradation were as follows:7.63%of inoculation size,685.4 mg·L^-1substrate concentration,59.43 mL shake flask volume,27.54°C temperature,and optimal theoretical phenol degradation rate of 23.42%,which were consistent with the verification test results.After screening and acclimation,strains with higher phenol degradation performance were obtained from samples collected from typical phenol-contaminated areas in the northern cold region of China.The strain was more suit for lower temperature in the northern cold region of China.