The anaerobic sulfur-reducing archaeon Pyrococcus furiosus was investigated regarding its capacity to desulfurize rubber material. The microorganism's sensitivity towards common rubber elastomers and additives was tested and several were shown to be toxic to P. furiosus. The microorganism was shown to utilize sulfur in vulcanized natural rubber and an increase in cell density was obtained when cultivated in the presence of spent tire rubber. Ethanol-leached cryo-ground tire rubber treated with P. furiosus for 10 days was vulcanized together with virgin rubber material (15% w/w) and the mechanical properties of the resulting material were determined. The increase in the stress at break value and the decrease in swell ratio and stress relaxation rate obtained for material containing microbially treated rubber (compared to untreated material) show the positive effects of microbial desulfurization on rubber.
Cryo-ground tire rubber was treated with the sulfur oxidizing bacterium Thiobacillus ferrooxidans in order to devulcanize the surface of the ground particles. The devulcanized rubber (15% (w/w)) was mixed with carbon black filled natural rubber, and subsequently vulcanized. The physical properties of the resulting material were examined. This study shows that the stress relaxation properties are improved due to the microbial treatment. The stress at break and swelling properties are also positively affected by this process.
Introduction
Grinding of Rubber Material
Recycling of Rubber Material
Biotechnological Processes
Historical Outline
Rubber Products to which Biotechnological Recycling is Applied
Microbial Degradation of Rubber
Surface Modification
Microbial Detoxification
Current State
Rubber as a Carbon Source for Fermentative Processes
Putative Products
Outlook and Developments
Acknowledgements
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