Characterization of microbial communities during a Ground Tire Rubber (GTR) desulfurization process

The present study aims at evaluating the effectiveness of bioreactor-based ground tire rubber (GTR) biodesulfurization process using two bacterial strains in two different bioreactors: i) Gordonia desulfuricans DSM 44462T, and ii) Rhodococcus sp. AF21875. Automated ribosomal inter-genic spacer analysis (ARISA), and High Throughput Sequencing of 16S rRNA gene amplicons were used to analyze samples collected from the bioreactors over time to detect the persistence of the inoculated bacteria within the autochthonous communities, and to compare communities in the bioreactors. Furthermore, the abundance of total bacteria (16S rRNA gene) and biodesulfurization potential (dszA) were estimated using qPCR, in the bioreactors and on GTR before the treatment. ARISA showed that G. desulfuricans DSM 44462T was able to persist, while there are no clear evidences of Rhodococcus sp AF21875 persistence into the bioreactor due to the presence of matching ARISA fragments in the untreated GTR. In both bioreactors, a high abundance of genus Gordonia and Rhodococcus was observed, with an increase of dszA copy numbers over time. Vulcanizates containing biodesulfurized GTRs showed better mechanical and rheological properties than an untreated GTR vulcanizate and even comparable with a natural rubber reference.