Preliminary results on the degradation of three microplastic polymers by rumen microbiota

The livestock sector is affected by plastics and microplastics (MPs) pollution. In fact, 50-60% of foreign bodies found in slaughtered domestic cattle are plastic-based materials, and MPs have been found in various matrices of ruminants including blood, faeces, follicular fluid, meat, and milk. A solution to this problem, could come from the ruminants themselves, in fact the microorganisms in the rumen have hydrolysis enzymes capable of degrading natural polyesters such as cutin; potentially these enzymes could also degrade synthetic polyesters, like polyethylene terephthalate (PET) and other commonly used plastic materials of livestock farms such as low-density polyethylene (LDPE) and polyamide (PA). Aim of this work was to study the rumen degradation ability to three MP powdered polymers: PET, LDPE, and PA. The rumen fluid was collected from a slaughterhouse and the MPs powders were provided by an Italian company. Approximately 0.5g of each MPs powder was placed in F57 bags (6 replicates for each polymer), for a total of 18 bags plus 2 empty bags. The 20 bags were incubated in the Ankom DaisyII Incubator for 24h (jar1), 48h (jar2) and 72h (jar3) along with 400mL of rumen fluid, 1600mL of buffer solutions and 20g of nutrients (ground Total Mixed Ration). Degradability was calculated by the following formula: (Pre-incubation MPs weight/Post-incubation MPs weight/Pre-incubation MPs weight)*100. LDPE and PA were not degraded at any incubation time, while PET was degraded progressively with increasing incubation time: 24h=0.54%, 48h=0.61% and 72h=0.82%. Future studies are needed to confirm these promising results.