Study of PLA pre‑treatment, enzymatic and model‑compost degradation, and valorization of degradation products to bacterial nanocellulose

It is well acknowledged that microplastics are a major environmental problem and that the use of plastics, both petro- and bio- based, should be reduced. Nevertheless, it is also a necessity to reduce the amount of the already spread plastics. These cannot be easily degraded in the nature and accumulate in the food supply chain with major danger for animals and human life. It has been shown in the literature that advanced oxidation processes (AOPs) modify the surface of polylactic acid (PLA) materials in a way that bacteria more efciently dock on their surface and eventually degrade them. In the present work we investigated the infuence of diferent AOPs (ultrasounds, ultraviolet irradiation, and their combination) on the biodegradability of PLA flms treated for diferent times between 1 and 6 h. The pre-treated samples have been degraded using a home model compost as well as a cocktail of commercial enzymes at mesophilic temperatures (37 °C and 42 °C, respectively). Degradation degree has been measured and degradation products have been identifed. Excellent degradation of PLA flms has been achieved with enzyme cocktail containing commercial alkaline proteases and lipases of up to 90% weight loss. For the frst time, we also report valorization of PLA into bacterial nanocellulose after enzymatic hydrolysis of the samples.