Biodegradation Of Polystyrene By Intestinal Microbes Of Galleria Mellonella Larvae

The pollution of discarded plastics and their undegraded characteristics have attracted widespread attention from all over the world.Polystyrene（PS）is a kind of petroleum-based plastic that has been widely used,and its non-degradability has brought serious environmental pollution problems.Recent works have shown that there may be some microorganisms with PS degraded ability in the gut of Galleria mellonella larvae.Based on this,this research carried out the following research works:Firstly,the gnawing ability of the larvae on PS foam（average PS consumption rate and survival rate of the larvae eating PS,etc.）was assayed;after feeding the larvae PS foam for 30 days,the Gel-permeation chromatography（GPC）,Thermal gravimetric analysis（TGA）,Fourier transform infrared spectroscopy（FTIR）,Nuclear magnetic resonance（~1H-NMR）and Gas chromatography-mass spectrometry（GC-MS）and other analytical methods were used to analyze the changes in the structure and composition of the compounds in the feces of the larvae after ingesting PS.The results indicated that there may be some PS-degrading bacteria in the intestines of the larvae,the analysis of microbial diversity in the tract has clarified the changes in the intestinal microbiome caused by feeding PS,and preliminary conclusions are drawn that the microorganisms of Firmicutes and Proteobacteria found in the intestines of PS-fed larvae may play a role in PS degradation.Subsequently,a PS degrading bacterium of the genus Massilia was screened and isolated from the gut of the larvae fed with PS foam and named as Massilia sp.FS1903.After co-cultivating the strain and the PS film on an inorganic salt solid medium for 30 days,the PS film was characterized.Scanning electron microscope（SEM）and Energydispersive X-ray spectroscopy（EDS）showed that the presence of FS1903 destroyed the structure and morphology of the PS film,and more oxygen elements appeared on the PS film after degradation;the change in the water contact angle（WCA）indicateed that the presence of FS1903 made the PS film change from hydrophobicity to hydrophilicity transition;X-ray photoelectron spectroscopy（XPS）further proved that more oxygen-containing functional groups were produced during the degradation of PS.In addition,after the PS film is co-cultured with FS1903 in shaking flask for 30days,the weight of the films were significantly reduced,with a weight loss of 12.97%±1.05%.The above results showd that Massilia sp.FS1903 has the ability to degrade PS and has possibility for the further application in the biodegradation of waste PS.Our research results provide important reference value for the effective biodegradation of PS.