Devulcanization of rubber crumb using sulfur oxidizing Archaea.

Abstract

Waste tires pose an ever-growing disposal and environmental problem. In the United States alone it is estimated that there are 2.5 billion waste tires sitting in landfills and this number is growing by 200 million every year. In order to recycle the rubber in these tires the rubber must be effectively devulcanized by breaking the carbon sulfur cross-links that are present. The need for a more cost-effective devulcanization process that produces rubber of higher quality has driven research in this field. It was the goal of my project to develop rubber recycling methods involving sulfur oxidizing Archaea and to determine the usefulness of these methods. In order to accomplish this goal two major methods were investigated: one using whole cells from the species Sulfolobus solfataricus P2, another using an enzyme, the sulfur oxygenase/reductase (Sor) from Acidianus ambivalens. My results have shown that both the whole cell method and the enzyme method oxidize the sulfur found in rubber crumb, thereby, causing some degree of devulcanization. An attempt was made to locate homologues to sor found in a number of species related to Acidianus ambivalens. Interestingly, after exhausting a number of methods, this search resulted in no homologue being found. The possibility of a novel form of sulfur metabolism is discussed.