Biodegradation of plastic waste by yellow mealworms (Tenebrio molitor larvae)

Plastics are very widely used worldwide, and most of these are not degradable, resulting in global environmental concerns. Plastic usage is growing faster than it did in the past, especially during the COVID-19 outbreak. Global plastic waste associated solely with this pandemic was estimated to be 8.4 ± 1.4 million tons in 2021, exacerbating the existing global burden of plastic, estimated at 9 billion tons produced up to 2017. Some insects can break down plastic polymers, and their intestinal microorganisms play an important role in the process. The purpose of this study was to investigate the biodegradation of several types of plastics by yellow mealworms (Tenebrio molitor larvae) and identify the intestinal bacteria engaged in the process.

In this study, a total of 140 g of mealworms (±1,050 individuals) were divided into seven groups consisting of approximately 150 larvae, and assigned to different plastic feeding conditions, i.e. polyvinyl chloride (PVC), polyethylene (PE), polystyrene (PS), polypropylene (PP), and polyethylene terephthalate (PET) for 30 days. The consumption rate of plastic, mealworm total live biomass retention, and the life cycle of mealworms were observed. The gut microorganisms of mealworms with the highest rate of plastic consumption were isolated and identified using 16S rRNA gene sequencing. Their potential for plastic degradation was assessed by testing their capability to grow in a minimal medium with PVC film serving as the sole carbon source.

After a month, PVC was consumed by mealworms more than other plastic sources, as evidenced by their regular life cycle and total live biomass retention (94.8702 ± 2.4278%). A bacterial strain (MG06) with potential PVC-degrading capability was isolated from the guts of the mealworms and was identified as Enterobacter xiangfangensis based on 16S rRNA gene sequencing and phylogenetic analysis. The strain demonstrated PVC-dependent growth and survival, indicating its potential to utilize PVC as a carbon source. To the best of our knowledge, no information regarding E. xiangfangensis concerning plastic degradation has been disclosed. This work reports the first evidence suggesting that this bacterium species may contribute to the biodegradation of PVC.