Biodegradation of pre-treated Low-Density Polyethylene (LDPE) by Yarrowia lipolytica determined by oxidation and molecular weight reduction

Abstract

Millions of metric tonnes of plastic waste are generated every year, with a minimal portion being recycled. Therefore, there is an urgent need to find effective and sustainable methods for plastic degradation, especially polyethylene, the most manufactured polymer globally. Here, we emulate the strategies documented for beetles, characterized by a combination of physical, chemical, and microbiological treatments, to biodegrade low-density polyethylene (LDPE). Importantly, we characterize LDPE degradation through multiple techniques, including weight loss analysis, FTIR, GPC, GC–MS, and SEM, which allowed us to identify the optimal combination of treatments to enhance LDPE biodegradation. Contrary to some expectations, we find that ultrasonication does not contribute to LDPE degradation but may instead protect against its fragmentation. However, we successfully introduce carbonyl groups into the polymer backbone, by simply exposing LDPE to environmentally friendly anionic surfactant. This pretreatment effectively cleaves LDPE by approximately 9%, breaking it into shorter carbon chains that are more accessible to microbes for subsequent biodegradation. The yeast Yarrowia lipolytica, isolated from fuel tanks and able to grow in n-paraffines, not only outperforms other microbes in assays of short carbon chain degradation, but also attaches to the LDPE surface, where it survives and grows using LDPE as sole carbon source. Our findings, therefore, pave the way for further developing a potential solution to plastic waste, calling for interdisciplinary research and innovative solutions in tackling global environmental challenges.