Study On Bio-detoxification Of Benzophenone-4 By Microorganism And Its Influencing Factors

Chemical UV filters are organic compounds that absorb harmful ultraviolet radiation.They are widely used in a variety of personal care products and sunscreen cosmetics,such as sunscreen,shampoo and body milk because they can effectively prevent ultraviolet radiation.Due to their extensive use,they are continuously released into the aquatic system,resulting in the"mixed persistent low dose"exposure characteristics in the environment.Benzophenone(BPs)is an important broad-spectrum chemical UV filters.Once it enters the natural aquatic system,it is not easy to be degraded.There are a large number of residues in surface water,domestic sewage and water sludge,and it is difficult for organisms to excrete through their own metabolism.Therefore,BPs can produce bioaccumulation and affect the ecosystem.It has been found that some BPs have obvious biological toxicity,especially endocrine disrupting effect,which are harmful to public health.In this study,2-Hydroxy-4-Methoxybenzophenone-5-Sulfonic Acid(BP-4)was selected as the research object,the aerobic activated sludge was domesticated to obtain the microbial flora with high degradation ability to BP-4.High throughput sequencing was used to analyze the changes of microbial community before and after acclimation of activated sludge to reveal the dominant degradation bacteria.The degradation rate of BP-4 was revealed under the condition of single carbon source and additional carbon source,the effects of different carbon sources on degradation were analyzed.The biological acute toxicity of the metabolic mixture system in the degradation process of activated sludge was monitored to reflect the detoxification effect during the degradation process.Two strains which degrading BP-4 were selected from the supernatant of acclimated activated sludge and identified.The results show that under the condition of BP-4 as the only carbon source,the activated sludge A(dry weight is 2.9 g/L)can completely degrade 20 mg/L in about 8hours,and activated sludge B(dry weight is 8.91 g/L)completely degrade 50 mg/L BP-4 within 8 hours.Five different amounts of sludge degradation experiments show that sludge amount is linear related to degradation rate,and satisfy the relationship K=0.5124×C_S.The results of TOC showed that the higher the sludge amount,the higher the mineralization rate of degradation process.The mineralization condition rate of 2 h under the condition of 8.9 g/L sludge concentration is 62.74%,and the shorter degradation time of 20 mg/L and 50 mg/L BP-4.Respectively,when adding additional carbon source(glucose),activated sludge A and B could significantly shorten the degradation time of 20 mg/L and 50 mg/L BP-4,which were about 6 h and 5 h.The acute toxicity of the different amount of sludge degradation was tested by Q67.It was found that the whole toxicity of the degradation process decreased,and finally the toxicity of the system decreased to no obvious toxicity.Through the analysis of microbial community,the community structure of the acclimated flora,such as strain Nakamurella,Rhodanobacter,Micriscillaceae,Thermomonas,etc.The abundance of strain Burkholderiaceae was high,and the growth rate of Nakamurella and Burkholderiaceae were large,among which Rhodanobaceraceae,Caulobateraceae,Steroidobaceraceae might be the main potential degrading strains providing degradation performance.Based on the isolation and purification of acclimated activated sludge,the strains with degradation performance were selected and identified as Pseudomonas aeruginosa and Comamonas testosteroni.