Comparative studies on the effectiveness of proteases and enzymes from dietary supplements in the degradation of polylactide (PLA)

Polylactide (PLA) has become one of the most widely used biodegradable plastics in recent years. The research focuses on solving the problem of its low-rate biodegradability under mesophilic conditions using cost-effective proteases of alternative origin. The aim of the study was to verify whether enzymes contained in food dietary supplements with the suggested high activity of protease enzymes could potentially be used for the degradation of PLA. The studies compare the activity of enzymes from dietary supplements with hydrolytic enzymes with scientifically proven effectiveness in degrading PLA. Products containing nattokinase, bromelain, papain and an enzyme mixture were tested. Their effectiveness against proteinase K, subtilisin and lipase was compared. From this group, proteinase K caused the greatest PLA mass loss and increase in O/C ratio after 28 days of incubation. The results indicated that nattokinase and papain caused a mass loss of PLA films similar to that of proteinase K, as well as a decrease in the carbonyl index value by more than 20%. Additionally, studies have shown that dietary supplements have a beneficial effect on the compost microflora. Causing an approximately 20-fold increase in the number of microorganisms within 48 h. In accordance with the assumptions, enzymatic products and their concentrations were selected that effectively accelerate PLA degradation in mesophilic conditions at a level comparable to or better than proteinase K, but have a much better effect on the substrate microflora, which makes them an interesting object for the development of products for accelerating the degradation of polymeric materials. In order to confirm the possibility of practical use of the results, an analysis of the phytotoxicity of the enzymes was carried out, which confirmed the possibility of using the enzymes in natural conditions.