Gut Microbiome and Degradation Product Formation during Biodegradation of Expanded Polystyrene by Mealworm Larvae under Different Feeding Strategies.

Emmanouil Tsochatzis,Konstantina Ntrallou,Francesca Tedeschi,Ida Elizabeth Berggreen,Milena Corredig,Helen Gika

doi:10.3390/molecules26247568

Emmanouil Tsochatzis, Konstantina Ntrallou + Show 4 more

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https://doi.org/10.3390/molecules26247568

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Abstract

Polystyrene (PS) is a plastic polymer extensively used for food packaging. PS is difficult to decompose and has low recycling rates, resulting in its accumulation in the environment, in the form of microplastic particles causing pollution and harming oceans and wildlife. Degradation of PS by mealworms (Tenebrio molitor) has been suggested as a possible biological strategy for plastic contamination; however, the biodegradation mechanism of PS by mealworms is poorly understood. It is hypothesized that the gut microbiome plays an important role in the degradation of PS by mealworms. This study carried out a comparative analysis of the gut microbiome of Tenebrio molitor larvae under different feeding strategies, and of the formation of degradation compounds (monomers, oligomers). A diet of bran:PS at 4:1 and 20:1 ratios was tested. The diet with the low ratio of bran:PS led to the presence of higher amounts of these compounds, compared to that with the high ratio. In addition, it was demonstrated that the addition of H2O significantly improved the biodegradation of PS monomer and oligomer residues, which could be identified only in the frass. The protein and nitrogen contents in insects’ biomass and frass varied amongst treatments. The diets resulted in differences in the gut microbiota, and three potential bacterial strains were identified as candidates involved in the biodegradation of PS.

Highlights

Plastic packaging is often associated with potential harm to the environment and human health [1]
The comparative study showed that bacteria from the families of Enterobacteriaceae (Erwinia olea) and Streptococcaceae (Lactococcus lactis and Lactococcus garviae) were more abundant in the gut samples of T. molitor fed with PS compared with the control, rendering them three of the most probable candidates playing a role in the biodegradation of PS
The data indicate that three fungal species, Sporobdomyces roseus, Alternaria alternata and Aspergillus versicolor, are more abundant in the gut samples of T. molitor fed with PS compared with the control

Summary

Introduction

Plastic packaging is often associated with potential harm to the environment and human health [1]. Its large production and low recycling rates result in high potential for its accumulation in the environment, with risks for the survival of wildlife and detrimental effects on human health [3,4]. Metabolomics studies have revealed the presence of several bioactive compounds, in both the bulk insects’ biomass and frass, such as long-chain fatty acids, esters and amides. It has been shown that alteration in feeding affects the ratio of these compounds, with several long-chain acids, in addition to hydrocarbons, present in connection with the presence of PS and its degradation [4,6,7]. The addition of PS to the diet causes the insects to experience metabolic stress, in comparison to a control diet [4,6,7]

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