Polyethylene-degradation Capacity In Dark-versus Yellow-mealworms(Larvae Of Tenebrio Obscurus Versus Tenebrio Molitor)

Polyethylene(PE),an extremely persistent synthetic polymer showing a high resistance to microbial attack,has been considered nonbiodegradable for decades.There are mainly four types of PE which are categorized by its density and branching.The three most common types of PE are high-density polyethylene(HDPE),lowdensity polyethylene(LDPE),and linear low-density polyethylene(LLDPE).Tenebrio obscurus(Coleoptera: Tenebrionidae)larvae are capable of biodegrading polystyrene(PS)but their capacity for polyethylene(PE)degradation and pattern of depolymerization remain unknown.Therefore,this study performed the research on "PE-degradation capacity in larvae of T.obscurus versus T.molitor",confirming the ability of T.obscurus and T.molitor to PE degradation.In addition,the effects of supplementary feedstocks and PE structure on PE degradation by the two Tenebrio species larvae are discussed.The conclusions are as follows:In this study,the T.molitor groups were capable of consumption PE at significantly higher consumption rates than those of T.obscurus.Compared with PE-fed larvae,significantly increase in PE consumption,survival rates and PE-degrading capacity have been achieved after wheat bran was supplied as co-fed with PE for T.molitor larvae and corn flour was supplied as co-fed with PE for T.obscurus larvae.As well as,corn straw and rice straw can be utilized as supplementary feedstocks to effectively increased PE consumption and degradation for both Tenebrio species larvae.PE consumption by both Tenebrio species larvae was closely with incubation condition.Better PE consumption were obtained by rearing 500 larvae with 2 g foams in a transparent polypropylene incubator(bottom area of 21 cm × 12 cm).During the incubation,the containers were maintained at 25 ± 0.5 °C with a humidity of 65 ± 5%in dark.High-temperature gel permeation chromatography(HT-GPC)analysis demonstrated that low molecular weight PE(<5.0 k Da)was rapidly digested while low molecular weight portions(>10.0 k Da)were broken down or cleaved,indicating a broad depolymerization pattern.Gut microbes in T.molitor and T.obscurus larvae were obviously inhibited by gentamicin.But the depolymerization of LDPE in both species did not stop.This showed that the larvae are capable of depolymerizing LDPE independent of gut microbes;and the biodegradation of LDPE in T.molitor and T.obscurus larvae is due to the synergistic action of larval digestive system and gut microbial activities.PE types significantly affected the biodegradability and reaction mechanism of both T.molitor and T.obscurus.The degradation ability to the three types of by the both Tenebrio species is in the order of LDPE> LLDPE> HDPE.The compounds of mealworms frass were analyzed by Py-GCMS,the differences of biodegradation productions in both species are revealing that the biodegradation pathway of PE polymers in T.obscurus larvae might be different to that in T.molitor larvae.The results of based on the 16 S r RNA genes high-throughput sequencing showed,the composition of the microbial communities was bound up with the different diets in the both Tenebrio species.Enterococcus is the dominant population in T.molitor and T.obscurus biodegraded PE.