Biodegradation of Natural Rubber: Microcosm Study.

In the present work, natural rubber (NR) biodegradation, by means of a microbial consortium, naturally selected in a tyre dump soil, has been evaluated. To this purpose, prepared soil microcosms were incubated for 236 days, at room temperature, and natural light/dark cycles. The effect of primary C-source and fresh soil addition, soil aeration, and humidity maintenance has been monitored by means of microbiological and respirometric analysis, dry weight loss determinations, and SEM micrographs. During the incubation, in biodegradation microcosms (BD), containing NR samples, the produced CO2 was significantly higher than that of biotic controls (BC). Furthermore, after 236 days, a NR dry weight loss of 15.6%, in BD microcosms, was registered, about four-fold higher than that registered in BC control (3.7%). Obtained results confirmed that the naturally selected microbial consortium was able to use NR as the only C-source and to biodegrade it. The positive effect of soil mixing evidenced that the biodegradation process was mainly carried out by aerobic biomass, especially filamentous fungi, as confirmed by microbial counts and SEM observations. Results obtained in the microcosm study provided useful information in terms of soil aeration and nutrient amendment in view of a future biodegradation process scale-up.