The Preliminary Study On The Degradation Characteristics Of Candida Tropicalis SDP-1 And Its Degradation Ability In Phenolic Environment

As an important organic industrial raw material,phenol is widely used in various chemical synthesis.At the same time,phenol also caused serious environmental pollution problems.Many countries have included phenol in the environment as a priority control pollutant.In order to solve the problem of phenol pollution,microbial degradation of phenol has attracted more attention due to its unique advantages.The main research of this study included the follow:To isolate highly efficient salt-tolerant phenol strains from a phenol environment.The growth characteristics and degradation characteristics of the strain were also studied.By analyzing the genetic information of the strain,the information of degradation was obtained and the strain was searched for the other features.Combined with experiments to verify the biological function of the strain,pot experiments were initially used to verify the potential growth-promoting properties.And whether the strain can reduce the damage of plant in phenol environment.The specific results are as follows:In this study,we based on a salt-tolerant phenol-degrading strain SDP-1 which isolated from silt in the coastal zone of Lianyungang.Then by the analysis of the morphology,physiology and biochemistry,ITS sequences of the strain SDP-1 to determine that the strain belongs to Candida.The growth characteristics of the strain revealed that the strain SDP-1 could grow in the range of 15-45°C and p H between 2.5and 10.5,the strain was able to tolerate Na Cl 12%?w/v?most.The strain has nice environmental tolerance.By optimizing the degradation conditions of strain SDP-1 and analyzing the addition of carbon and nitrogen sources to the culture medium,the optimum degradation conditions of strain SDP-1 were obtained.Under the optimal phenol degradation conditions,1200 mg/L phenol can be completely degraded within24 hours.The strain SDP-1 had good resistance to heavy metal ions such as Mn²⁺,Zn²⁺and Cr³⁺at high concentrations during phenol degradation.The results of broad spectrum the degradation substrate of strain SDP-1 showed that strain SDP-1 has good degradation potential for various benzene ring compounds.The strain SDP-1 expressed catechol 1,2-dioxygenase activity under phenol-containing conditions,but it did not express catechol 2,3 dioxygenase activity.The activity of catechol 1,2-dioxygenase and catechol 2,3-dioxygenase cannot be detected without phenol,so catechol1,2-dioxygenase activity is only induced to be expressed when the environment contains phenol.By immobilizing the strains,it was found that the time required for the complete degradation of phenol by the immobilized strains was shorter than that of the free strains with the increase of the phenol concentration.And the time was shortened by 8 hours when the phenol content was 1500 mg/L.Under the condition of high salt concentration,the complete degradation time of the immobilized strains was shorter than that of the free strains by 4 hours under the 3%salt concentration condition,and the same condition the immobilized strains was shorter than that of the free strains by 12 hours under the 5%salt concentration.In the soil environment,the immobilized strains also showed better phenol degradability than the free strains,especially with the increase of phenol and salt concentration.In a 1000 mg/kg phenolic soil,the time for the complete degradation of phenol by the immobilized strains was shorter than that of the free strains by 8 days without salt.When the salt content in the soil was 3%,the free strains take more than 8 days to be completely degraded than the immobilized bacteria.In the degradation of actual phenolic wastewater,the immobilized strains have better degradation effect than free strains.And the immobilized strains can more significantly reduce the COD value in the water than free strains.Even in the high-concentration phenol-containing wastewater,the immobilized strains and the free strains all cannot completely degrade phenol.But the immobilized strains could also degrade 9.4%of the phenol and then stabilized,while the free strains could hardly degrade the phenol in the wastewater.The COD value was 5.42%lower than that of the free strains treatment.In the correlation analysis of the genomic information of the strain SDP-1,the gene of phenol degradation was found.Only the phenol hydroxylase gene,catechol1,2-dioxygenase gene was found and catechol 2,3-dioxygenase was not found.Enzyme-associated genes validated previous experiments,that is,strain SDP-1 degrades phenol by ortho-way opening.In addition,the genes related to salt tolerance and heavy metal tolerance of strain SDP-1 were also found in the genomic information of strain SDP-1,which was consistent with previous experimental data.Genomic information also revealed that the genes that promoted the growth of the tomato seedlings were validated by pot experiments.In the study of the combination of strains and plants to improve phenol-containing soil,the inoculation strain SDP-1 can reduce more than 99%phenol in soil.At the same time,the plant height increased by 49.95%,the fresh weight increased by 164.86%,the total chlorophyll content increased by 91.62%and the MDA content reduced by 23.94%compared with the phenol control group.In this study,a high-salt phenol-containing environment was used as a potential pollution control object.The relevant characteristics of microbial degradation of phenol were discussed,and the optimal phenol degradation conditions of the strains were obtained,which providing a theoretical basis for subsequent application to production and process optimization.The study based on the genome information of the strains,tomato pot experiment was carried out to verify the effect of the strains on tomato growth and reduce the damage of tomato in phenolic environment.Subsequent to this study will be an in-depth study of the combination of plants and microbes to repair the phenolic environment.