Can Insects Break Down One of the Most Persistent Plastics? A New Discovery Involving Mealworms and PVC

Plastic pollution has become one of the most frequently discussed environmental issues in recent years. Since humans first invented plastic, large quantities of materials that are extremely difficult to degrade have accumulated in the environment, including polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC). Among these, PVC has long been regarded as particularly problematic.

The polymer chain of PVC contains a large number of chlorine atoms (–CH₂–CHCl–). This chemically complex structure gives the material exceptional resistance to corrosion, durability, and electrical insulation, making it widely used in engineering, household products, and many industrial applications. However, the same properties that make PVC useful also create environmental problems. When burned, it can generate highly toxic pollutants such as dioxins, and when discarded in soil it decomposes extremely slowly. Because of these concerns, PVC has gradually been phased out of some everyday consumer products.

Figure 1. Reaction scheme and molecular formula of polyvinyl chloride (PVC)。圖片來源：Jü，CC0 1.0 公共領域。

Figure 2. PVC pipes, a common PVC product。圖片來源：Стрелец Игорь，採用 CC BY 3.0 授權。

But is PVC truly as indestructible as it has long been believed? In attempts to address the challenges posed by this persistent plastic, scientists have begun turning their attention to an unexpected group of organisms: insects. As early as 2017, researchers discovered that certain insects, including the greater wax moth (Galleria mellonella) and the mealworm (Tenebrio molitor), appeared capable of breaking down plastics such as polyethylene (PE) and polystyrene (PS) through the activity of symbiotic microorganisms living in their digestive systems.

Figure 3. Mealworm (Tenebrio molitor)。圖片來源：Mnolf，採用 CC BY-SA 3.0 授權。

Figure 4. Greater wax moth (Galleria mellonella)。圖片來源：pour，採用 CC BY-NC 4.0 授權。

However, early research was largely limited to relatively simple polymers such as PE and PS because of technical limitations in analytical methods. In comparison, PVC—with its chlorine-rich and structurally complex polymer backbone—was widely considered a material that biological systems could not degrade.

This assumption began to change in 2026. A study published in the journal PeerJ titled “Biodegradation of plastic waste by yellow mealworms (Tenebrio molitor larvae)” challenged the long-standing belief that PVC is biologically resistant to degradation. Building on earlier work on insect-mediated degradation of plastics such as PS and PE, the researchers fed mealworms several common plastic products, including PVC plastic wrap, PP-B soft plastic bags, PP-C rigid plastic containers, LDPE opaque plastic bags, and PET beverage bottles.

Figure 5. Daily consumption trends of five plastics by mealworm larvae over 30 days. During the 30-day experiment, the daily consumption of five plastics by mealworm larvae included polyvinyl chloride (PVC), low-density polyethylene (LDPE), polypropylene plastic bags (PP_B), polypropylene plastic containers (PP_C), and polyethylene terephthalate (PET). The data represent the average daily mass (g) of each plastic consumed, reflecting the consumption rate and preference of yellow mealworms for different plastics. Error bars represent the standard deviation from three replicate experiments (n = 3).。圖片來源：Srisakvarangkool et al，採用 CC BY 4.0 授權。

Figure 6. Weight reduction of different plastics consumed by mealworm larvae over 30 days. The bar chart shows the total mass reduction after mealworm larvae consumed several plastics (PVC, LDPE, PP-B, PP-C, and PET). Statistical analysis revealed significant differences in mean mass reduction between at least two groups (p < 0.0001). Holm-Sidak multiple comparisons indicated significant differences between the PVC and PP-B groups (p = 0.0019) and between the PP-B and LDPE groups (p = 0.0065). Different letters above the bars indicate statistically significant differences among groups.。圖片來源：Srisakvarangkool et al，採用 CC BY 4.0 授權。

Figure 7. Live biomass retention of mealworm larvae fed different plastics and control diets. This study compared the live biomass retention of mealworm larvae across several feeding treatments, including rice bran (positive control), PVC, PP-B, PP-C, PET, and an unfed negative control. One-way analysis of variance (ANOVA) revealed significant differences in biomass retention among at least two groups (p < 0.0001). The rice bran group and the PVC group showed the highest biomass retention, with no statistically significant difference between them (Holm-Sidak multiple comparison test, p = 0.9483). The PP-C group, PET group, and the unfed negative control showed the lowest biomass retention, with no significant differences among them (p > 0.05). Different lowercase letters above the boxes indicate statistically significant differences among groups。圖片來源：Srisakvarangkool et al，採用 CC BY 4.0 授權。

Figure 8. Pupation rate of mealworms fed different plastics over 30 days. The heat map shows the pupation rate of mealworm larvae fed different plastic types during the 30-day experiment. Dark red indicates a higher pupation rate (dark red = 6), whereas light blue indicates no pupation (0). The dendrogram above the heat map shows similarities in daily pupation numbers among feeding groups, clustering groups with similar pupation responses. The positive control group and the PVC-fed group exhibited very similar pupation rates, both lower than those of the PET-fed group, the PP-C-fed group, and the unfed negative control group。圖片來源：Srisakvarangkool et al，採用 CC BY 4.0 授權。

To evaluate the effects of these diets, the researchers compared the plastic-fed groups with two control treatments: a positive control group fed rice bran and a negative control group given no food. After 30 days of feeding, the results were striking. Mealworms consuming PVC showed no significant loss of body mass, and their survival rate was similar to that of the rice-bran control group. They were able to complete their life cycle and develop into adult beetles without displaying the premature maturation that typically occurs under starvation conditions. These observations suggest that mealworms possess a physiological mechanism that allows them to utilize PVC as part of their energy supply.

To better understand the origin of this capability, the researchers shifted their focus to the gut microbiome of the mealworms. First, the larvae were surface-sterilized with alcohol to eliminate external microbial contamination. The digestive tracts were then dissected, and the gut contents were homogenized to isolate the symbiotic microbial community. These microorganisms were subsequently cultured in a carbon-free basal medium in which a PVC film served as the sole carbon source.

The results demonstrated that the symbiotic bacteria could not only survive in this environment but also grow using PVC as their only carbon source. This confirmed that the microorganisms were capable of metabolizing PVC.

Figure 9. Symbiotic bacteria isolated from the gut of mealworm larvae fed PVC, cultured on nutrient agar. The isolates shown are: (A) MG01, (B) MG04, (C) MG06, and (D) MG07。圖片來源：Srisakvarangkool et al，採用 CC BY 4.0 授權。

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Figure 10. Morphological characteristics of bacterial strains isolated from the gut of PVC-fed mealworm larvae. (A) Colony morphology on nutrient agar plates. All isolates show similar characteristics: yellow-white, opaque, circular colonies with undulating edges, convex surfaces, and smooth texture. (B) Gram-stained microscopic image showing rod-shaped Gram-negative bacteria。圖片來源：Srisakvarangkool et al，採用 CC BY 4.0 授權。

Figure 11. Visual comparison of bacterial growth in liquid carbon-free basal medium (LCFBM) with and without PVC film. Panels A and C show cultures without PVC film, while panels B and D show cultures with PVC film. (A, B) represent cultures after 3 days, and (C, D) represent cultures after 60 days. In the presence of PVC film (B, D), bacteria appear to attach to the plastic surface, particularly after prolonged incubation (D). In the negative control without PVC film (A, C), no obvious bacterial attachment or growth is observed。圖片來源：Srisakvarangkool et al，採用 CC BY 4.0 授權。

To identify the bacteria involved, the researchers used 16S rRNA gene sequencing. This widely used technique relies on the highly conserved sequences within the 16S component of the prokaryotic 30S ribosomal subunit to determine species identity and reconstruct phylogenetic relationships. Sequence comparison and phylogenetic tree analysis showed that the isolated strains shared more than 99.9% similarity with Enterobacter xiangfangensis. The bacteria responsible for PVC degradation were therefore identified as Enterobacter xiangfangensis.

Figure 12. Phylogenetic tree based on 16S rRNA gene sequences showing the relationships among bacterial isolates obtained from the gut of PVC-fed mealworm larvae。圖片來源：Srisakvarangkool et al，採用 CC BY 4.0 授權。

Although the discovery of a PVC-degrading symbiotic bacterium is exciting, the authors of the study emphasized that the findings represent only an early step in understanding the process. Many aspects of the symbiosis between mealworms and this bacterium remain unresolved. For example, the precise enzymatic mechanisms that allow the microbe to break down PVC's chlorinated polymer structure are still unknown. It is also unclear whether intermediate metabolic products could generate secondary pollution, or how completely the plastic can ultimately be reintegrated into the natural carbon cycle.

Nevertheless, there is reason for cautious optimism. This research not only opens new possibilities for the biological treatment of PVC waste but also highlights how natural systems may already contain solutions to problems created by human technology. In the future, strategies such as microbial strain screening, genetic engineering to enhance degradation pathways, or the integration of insect-rearing technologies could potentially lead to low-cost and efficient systems for the biological processing of PVC. If such approaches succeed, the end of the “plastic age” may no longer mean permanent environmental contamination, but instead a transition toward truly circular and sustainable material use.

Author: Rodrigo

Reference:

Srisakvarangkool, W., Chanthasena, P., Rosyidah, A., Ganta, P., Kerdtoob, S., & Nantapong, N. (2026). Biodegradation of plastic waste by yellow mealworms (Tenebrio molitor larvae). PeerJ, 14, e20429. https://doi.org/10.7717/peerj.20429