Biodegradation And Mechanism Of Dimethyl Phthalate By Phanerochate Chrysosporium

Dimethyl phthalate(DMP)is one of the most important and widespread PAEs in the industry.Because it does not chemically bond with the main polymer,it is easy to leach from the plastic into the environment through the food chain into mammals and harm the health of living organisms.At present,the main methods to degrade DMP are photochemical oxidation,pre-oxidation and biodegradation.Due to its advantages of low energy consumption,low cost,and negligible secondary pollution,biodegradation has become a hot choice for remediation of organic compounds polluted environment.White rot fungi have a special enzyme system and a large specific surface area,Thus,it can completely degrade all kinds of organic pollutants that are difficult to degrade.In view of this,Phanerochaete Chrysosporium is taken as the representative of white rot fungi and Dimethyl phthalate(DMP)is taken as the target contaminant in this project.The optimal degradation conditions of DMP by P.chrysosporium,the changes of peroxidase under different environmental factors,the degradation products and the analysis of mechanism were systematically studied.The main research contents are as follow:Single factor experiment to determine the best reaction conditions for the degradation of DMP by P.chrysosporium.It was determined that Tien and Krik medium was used as the liquid medium for cultivating P.chrysosporium.The method of adding pollutants after the spores grew for 3 days to become fungi pellets was used as the pollutant dosing method for subsequent experiments.When T=30?,pH=5.6,and the initial DMP concentration is 10 mg/L,the degradation efficiency after reaction 7 reaches 75%,while the degradation efficiency of the blank control and adsorption control is much less than20%,which shows that the disappearance of DMP is due to Biodegradation rather than adsorption.Optimize the reaction conditions:when the glucose concentration in the system is 5 mg/L,the degradation efficiency can reach 95%.When 20?g/L H₂O₂or 27mg/L Mn²⁺is added to the system,the degradation efficiency of DMP can be significantly increased to 100%.Changes of peroxidase under different environmental factors.It was found that under the stress of 10 mg/L DMP,the activities of MnP and LiP in the whole reaction stage were higher than those in the control group(only P.chrysosporium).This indicated that the existence of DMP stimulated the secretion of MnP and LiP.In the coexisting system of P.chrysosporium/DMP/Mn²⁺,the activity of MnP enzyme was higher than that of the MnP secreted by P.chrysosporium/DMP coexisting system,but the activity of LiP was reduced.This shows that Mn²⁺can promote the secretion of more MnP by the P.chrysosporium,but it has an inhibitory effect on the production of LiP.In addition,the experiment also found that adding an appropriate amount of H₂O₂to the system can promote the secretion of LiP by the P.chrysosporium.Enzyme degradation experiments show that extracellular enzymes can degrade DMP well.The optimal conditions for degradation of DMP by extracellular enzymes of P.chrysosporium are determined:the initial pH is 5.6 and the initial concentration of DMP is 1 mg/L,the degradation efficiency of DMP was 52%.Fourier transform infrared spectroscopy determines the main functional groups on the surface of the fungi.In the biodegradation process of DMP,the functional groups such as carboxyl and hydroxyl in Phanerochaete Chrysosporium play an important role.Substances such as salicylic acid and monomethyl phthalate were detected,and three degradation pathways of Phanerochaete chrysosporium to DMP were speculated:(a)side chain condensation to ring(b)benzene ring opening(c)Methylation.