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 13 CO 2 from 13 C-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 13 C-PE with the highest 13 C-mass loss of 0.199% recorded for UV-treated 13 C-PE with yeast extract, after 14 days incubation. In this study, we demonstrated the mineralization of 13 C-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. • Bacterial 13 C-PE mineralization was evaluated by stable isotope tracing assays. • Bacillus velezensis MT9 mineralizes Untreated and UV-treated 13 C-PE powder. • Up to 0.199% mass loss was observed for UV-treated 13 C-PE in 14 days. • UV and yeast extract enhanced 13 C-PE mineralization by B. velezensis . • Vreelandella cultures showed no mineralization activities toward untreated 13 C-PE.