Mineralization of 13C-labeled polyethylene by marine Bacillus velezensis MT9

In the marine environment, plastic debris breaks down into smaller entities known as microplastics. Polyethylene (PE) is the main source of microplastics. In a previous study, we showed that marine Bacillus MT9 and Vreelandella strains (MT1, MT11) were able to degrade untreated PE based on SEM, gravimetric weight loss and FTIR analysis. In this study, we performed stable isotope tracing assays, measuring the production of 13CO2 from 13C-PE powder (untreated or UV-treated) incubated with B. velezensis MT9, V. titanicae MT11 or V. venusta MT1 isolates under aerobic conditions in the presence and absence of yeast extract as co-nutrient source. Only B. velezensis MT9 exhibited mineralization activities towards untreated and UV-treated 13C-PE with the highest 13C-mass loss of 0.199% recorded for UV-treated 13C-PE with yeast extract, after 14 days incubation. In this study, we demonstrated the mineralization of 13C-PE by B. velezensis MT9. Furthermore, we also confirmed that photodegradation of plastic is a key process to enhance the biodegradation of PE. These findings suggest that Bacillus sp. could potentially degrade PE plastic waste in marine environment, as they can slowly mineralize PE even when other nutrients are present.