Polystyrene Biodegradation by Tenebrio molitor Larvae: Identification of Generated Substances Using a GC-MS Untargeted Screening Method

Abstract

A GC-MS method has been applied to screen and evaluate the generation of chemical compounds during the biodegradation of polystyrene (PS) with Tenebrio molitor larvae. Several resulting compounds have been identified, including trimers 2,4,6-triphenyl-1-hexene and 1,3,5-triphenylcyclohexane, the volatiles acetophenone and cumyl alcohol, and 2,4-di-tert butylphenol, a non-intentionally added substance (NIAS) present in the plastic material. The PS monomers styrene and α-methyl styrene were also identified in the extracts. Bioactive molecules present in the biomass of the studied insects were identified, such as the free fatty acids myristic, palmitic, and oleic acid. Undecanoic acid was also found, but in lower mass fractions. Finally, biochemically formatted amides resulting from their respective fatty acids were identified, namely tetradecanamide, hexadecanamide and oleamide. The formation of all these substances seems to suggest enzymatic and biochemical activity occurring during the biodegradation of PS, and their amounts varied throughout the experience. The overall degradation rate of PS resulted in a 13% rate, which highlights the potential of biorecycling using these insects.

Tenebrio molitor in the circular economy: a novel approach for plastic valorisation and PHA biological recovery

“…This trend can be explained by the enzymatic conversion of ingested compounds into CO 2 , as already reported by Yang et al (2015c). In parallel, Tsochatzis et al (2021) identified several bioactive components, such as myristic, palmitic and oleic acids and their respective amides. The authors concluded that the absence of hazardous chemicals in TM biomass and the presence of bioactive molecules suggest that plastic biodegradation by TM appears to be a valid bio-recycling process.…”

“…In a 7-day test, they identified several oligomers resulting from PS biodegradation, such as PS monomers (e.g. styrene, α-methyl styrene, acetophenone), oligomers and other unintentionally added substances (Tsochatzis et al 2021). For all residual substances (except α-methyl styrene which reaches a plateau up to day 7), after an initial increase from day 1 to day 3, a decrease is observed on day 7.…”

“…Furthermore, there are currently regulatory gaps in these fields. Some scientific work on TM larvae fed with different diets supplemented with PS waste suggested the absence of hazardous chemicals in TM biomass accompanied by the presence of bioactive molecules (Brandon et al 2020;Tsochatzis et al 2021). Then, including this novel nutrition form could enhance TM value.…”

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

“…There is an increasing interest in the biodegradation of plastics, by microbial activity or specific enzymatic activity. In particular, studies have reported the potential degradation of PS using different insects: mealworms (Tenebrio molitor) [4][5][6][7][8][9][10], superworms…”

“…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. Furthermore, 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].…”