Rapid biodegradation of plastics by mealworms (larvae of Tenebrio molitor) brings hope to solve wast plastic pollution

Plastic waste pollution in soils, rivers, oceans, and even landfills and potentially groundwater has been a major environment concern for decades. Plastic particles could penetrate into groundwater and become potential threats to our groundwater. The most common waste plastics include polystyrene (PS) and polyethylene (PE). Our recent research demonstrated that mealworm (larvae of Tenebrio molitor), which are commercially used as animal feed and insect protein, can biodegrade PS and convert up to 48% of it to CO2 within 12-20 hrs in mealworm gut. PS degradation is performed initially via fragmentation by the mealworm and then degradation within the mealworm guts. Gut microbiota play a major role in PS biodegradation because the degradation is almost completely inhibited when mealworms were fed antibiotics. Physical and chemical analysis as well 13C labeled tests confirmed the biodegradation and mineralization of PS. The ubiquity of PS eating behavior and biodegradation has been observed by testing mealworms from 11 different sources from China and the USA. All of the mealworms tested consume PS although at different relative rates. At ambient temperature (20-24 oC), the average daily consumption rate of PS ranged from 0.1 to 0.3 mg per 100 mealworms when fed PS alone. The mealworms also consumed low density polyethylene (LDPE) foam as sole diet. When mealworms were fed PS alone, the consumption rate and total amount consumed increased slightly as a function of temperature from 20 to 30 oC. Supplementing the diet with their normal food (bran) enhanced the PS consumption rate and the total PS mass consumed. Microbial community analysis indicated that the microbial structure changed significantly after the diet was switched from normal food bran to PS or PS plus bran. PS-degrading bacterial strains have isolated and characterized. Our discoveries brings hopes to prevent or solve potential micro plastics threats to groundwater.