| In recent years,the number of marine microplastics has increased dramatically,and microplastics have also been identified as a new pollutant that has direct or indirect effects on marine organisms,affecting their growth,development,reproduction,and so on.Microplastics can even affect human health through the transmission of biological chains.Therefore,it is urgent to control marine micro plastic pollution.The way to solve the pollution of marine microplastics can be to reduce plastic production,reduce land-based input,reduce human fishing activities at sea,and reduce the number of trips to the beach,but there are certain unreasonable aspects.With the rapid development of human society,plastics play a pivotal role in human production and life.Reducing the use of plastics is a long-term strategy that cannot be achieved overnight;Humans can reduce the terrestrial input of marine microplastics by burning and burying waste garbage,but there are drawbacks such as high economic costs and secondary pollution;It is also unrealistic to reduce human production activities in the ocean and consume large amounts of seafood.Therefore,it is necessary to seek an efficient,economical,and non secondary pollution method to solve the pollution of marine microplastics.This article uses microorganisms to degrade marine microplastics,which is an environmentally friendly solution.The experiments in this article mainly include screening efficient PE degrading bacteria from sponge co epiphytic microorganisms,optimizing environmental conditions for degradation,improving degradation rates,and exploring the degradation of PE on other microplastic films.(1)41 strains of PE degrading bacteria were selected from sponge animals.Through the study on the degradation ability of the 41 strains of PE degrading bacteria isolated,3 strains were selected for physiological,biochemical,and 16S rDNA identification.The results showed that the strain HM2 was Paracoccus serinephalus strain NBRC,the strain HM18 was near Halomonas denitrificans strain VS-7,and the strain NM23 was Pseudomarina primary strain 90.(2)According to the test results of three single factor experiments of temperature,salinity,and pH,the optimal temperature is 28 ℃,the optimal salinity is 35 ‰,and the optimal pH value is 7.5.The three factors that affect the degradation rate of polyethylene films are: pH(C),temperature(A),and salinity(B).There is a significant interaction between salinity(B)and pH(C),while the interaction between temperature(A)and pH(C)is not significant,and the interaction between temperature(A)and salinity(B)is not significant.The response surface optimization model was used to predict the optimal conditions.The initial temperature,salinity,and pH values were28.49 ℃,35.02 ‰,and 7.64.The predicted response value was 1.69%,and the actual degradation rate was 1.62%.The predicted value was relatively close to the actual value,indicating that the model was reasonable and could better predict the actual situation.(3)The microscopic characterization of polyethylene film by HM2 strain was observed by field emission scanning electron microscopy,and cracks and holes appeared on the average surface of the film,verifying the degradation effect of HM2 strain on polyethylene film.By comparing the size of the pores,it can be found that the pores that appear after the response surface optimization of experimental conditions are larger than before,verifying that the optimization of experimental conditions can improve the biodegradation efficiency of microplastics.(4)By measuring the degradation rate and the pH of the culture medium,the degradation characteristics of HM2 strains on different microplastics were investigated.Among the polyolefin plastics tested,the quality of PE microplastics,LDPE microplastics,HDPE microplastics,PPmicroplastics,and PVC microplastics has varying degrees of loss,with PE microplastics having the highest degradation rate and PVC microplastics having the lowest degradation rate. |
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