Identification of Tetrathionate Hydrolase from Thiobacillus Ferrooxidans: An Enzyme Responsible for Enzymatic Devulcaniz
Malaysia is one of the largest producers of rubber and as a result produces million tonnes of vulcanized rubber waste from the rubber-based industries each year. Currently, less than 13 % of the waste tires generated annually are recycled by any means sin
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R. Pogaku et al. (eds.), Developments in Sustainable Chemical and Bioprocess Technology, DOI: 10.1007/978-1-4614-6208-8_24, Springer Science+Business Media New York 2013
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M. D. Azratul and Y. Faridah
with salt concentration as follows: in (g/l) of KH2PO4 = 4 g, (NH4)2SO4 = 4 g, and MgSO4.7H2O = 0.3 g. After preparing the initial sample, it was found that the specific activity of extracellular and intracellular tetrathionate hydrolase occurred on Day 1 and 2 is 0.070 lmol min-1mg-1(U/mg) and 0.274 lmol min-1mg-1 (U/mg), respectively, at pH 4, 25 C. Future work includes reaction of purified tetrathionate hydrolase with used rubber to observe the devulcanization process. This work is important mainly because it is an environmental friendly and safe method of devulcanization and with thorough study, it is hoped that the objective to recycle higher percentage of waste rubber can be achieved.
Keywords Enzymatic devulcanization Thiobacillus ferrooxidans Tetrathionate hydrolase
Introduction After Thailand and Indonesia, Malaysia is the largest producer of rubber and has greatly contributed to the expansion of rubber technology in the present world. The technology of rubber creates a variety range of products such as rubber gloves, storage tanks, and insulation of electrical devices; however, the most important one is its usage in tire industries. The advancement of tire industries started in 1839 when Charles Goodyear discovered that by boiling crude rubber along with sulfur in solution produced an improved rubber material (Lewin 2004) which results in the production of vulcanized rubber tires. The advantages are good tensile strength, resistance to temperature changes and organic solvents as well as extreme elasticity. However, after these tires are no longer in use, they will be disposed to the environment. The biggest challenges are when the discarded vulcanized rubber tires are not biodegradable due to their sulfur cross-linking and have become one of the major sources of pollution. Disposal of waste tires and its recycling give a big task to mankind because the accumulation of discarded waste tires leads to environmental pollution (Gulzad 2011). To date, there is no environmentally sound and economically viable method to recycle or dispose-off the vulcanized scrap tires. The only environmentally sound way to dispose vulcanized scrap tires in large quantity is to burn it in the cement kiln (E-Waste Management 2008). Vulcanized scrap tires virtually indestructible if left in the dump site as it cannot biodegrade even in 50 years. Environmental laws had forbidden the burning of scrap tires because burning tires emits a lot of black smoke and harmful chemicals. Dump site for scrap tire heaps is space consuming, fire hazard and health hazards due to mosquito breeding (U.S. Environmental Protection Agency 1993). Therefore, there is an urgent need to search for a safe recycling method to reduce the scrap tire threats. One of the methods is retreading the tires which it is carried out via devulcanizatio
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