Characteristics Of Foam Plastics Ingestion And Degradation By Zophobas Atratus Larvae,and The Gut Functional Microbiome

Plastic is a kind of polymer with light weight,portable,cheap,good ductility and strong chemical stability,etc.,widely used in life.However,because it can hardly be naturally degraded in the environment,a large amount of plastic waste in our life has caused serious damage to the natural environment.At present,the main methods to deal with plastics are landfill and incineration,but these two methods cannot completely solve the problem of plastic pollution,and both of them would cause secondary pollution to the environment.Therefore,it is urgent to study new methods for harmless and resourcebased treatment of plastics.Some studies have indicated that the Zophobas atratus larvae can feed on and degrade plastics,but there is no relevant research on the efficiency of Z.atratus feeding on plastics and the characteristics of gut functional microorganisms.In this study,the growth of Z atratus feeding on plastic under different environmental conditions and the net weight change of plastic were explored.In addition,the changes of digestive enzyme activities in the digestive tract and the physiological characteristics of worms fed on polystyrene(PS),polyethylene(PE)and polyurethane(PU)were compared.Infrared spectroscopy and thermogravimetric analysis were used to analyze the composition and thermal stability of the frass of the larvae.It was proved that the Z.atratus could degrade the three kinds of plastics.The structure of dominant microflora in the gut of Z.atratus was analyzed by high-throughput sequencing technology to guide the isolation of functional.LB medium and MRS medium were selected to isolate the bacteria in the gut of plastic-feeding worm,and the 16S rRNA sequencing technology was used to identify the molecular biology of the isolated strains,which laid a foundation for the subsequent isolation and verification of the functional bacteria degrading plastics.Through the experiment,it is found that:(1)The growth and plastic feeding efficiency of Z.atratus larvae were affected by light,water supply,plastic density and plastic contact area.Dark conditions and daily water supplementation of 1ml were more conducive to the growth of worms and plastic feeding.Larvae have better feeding effect on foam with low density,high foaming degree and low breaking degree.After optimizing,the survival rate of the worm was significantly improved,and the 35-day feeding efficiency on plastic foam of Z.atratus was increased from 19.8 mg/worm to 51.3 mg/worm.(2)Among the three kinds of plastics,PS,PE and PU,the Z.atratus larvae had better feeding effect on PS plastic and worst feeding effect on PE plastic.Fourier infrared spectroscopy and thermogravimetric analysis were used to analyze the frass of larvea,it is found that the structure,composition and thermal stability of the plastics in the frass were significantly changed after the digestion,and new substances were produced,which proved the degradation of the three plastics by the larvea.(3)The digestive enzyme activities in the gut of Z.atratus after feeding on plastic were analyzed.It was found that there were significant differences in the digestive enzyme activities of larvea after feeding on PS,PE and PU plastics.Among them,the lipase activity of plastic-fed was higher than that of the bran-fed group,which was speculated to be because the larvae converted into body fat by degrading plastic and thus increased the lipase activity.(4)The results of high-throughput sequencing showed that the dominant microflora in the gut of Z atratus changed after feeding on plastic,which was related to the type of plastic that the worms fed on.Classified as Unclassified Enterobacteriaceae,Dysgonomonas,Sphingobacterium,and Enterococcus.which may be associated with PS plastic degradation,while Enterococcus and Citrobacter are related to PE degradation;Enterococcus and Mangrovibacter are related to PU degradation.In addition,nine different strains were isolated from LB medium and MRS medium,and the molecular biological identification results showed that most of the isolated strains belonged to Enterobacteriaceae,which was in line with the high-throughput sequencing results.