Thermus brockianus

In the steamy waters lives a type of bacterium that could help make industrial bleaching cheaper and more environmentally friendly. Scientists have discovered that Thermus brockianus produce a hardy enzyme that can be put to work by breaking down hydrogen peroxide in industrial wastewater, producing only harmless oxygen and water as byproducts. Most important, the so-called extremozyme endures harsh industrial conditions better than currently available alternatives and lasts thousands of times longer.

T. brockianus cells are gram-negative bacteria. T. brockianus is assumed to have a pilus-like structure. Thermus has an optimum growth temperature of between 70°C and 75 °C (min: 37-45°C, max: 79°C), though some have lower growth temperatures of about 60°C (min: 35-40°C, max: 70°C). High temperature T. brockianus pH ranges between 7.5 and 8.0, though strains grow as low as 5.1 and as high as 9.5. No strain of T. brockianus appears to be capable of fermentation.

T. brockianus strains use several substrates for growth, including carbohydrates, amino acids, carboxylic acids, and peptides. Because of the diversity in habitat from which T.brockianus strains are isolated, the nutritional diversity also has a large variety. T.brockianus strains often use monosaccharides as a source for single carbons, though typically pentoses are not metabolized.

For many high-temperature strains of T. brockianus, nitrate is used as a terminal electron acceptor and T. brockianus grows anaerobically in the presence of it.

T. brockianus have been found in both shallow and deep-sea marine hydrothermal systems, as well as in low saline solfataric springs.

Since the 1980s, cloth and paper manufacturers and other industries have experimented with using hydrogen peroxide instead of toxic chlorine bleach to whiten and disinfect products. Hydrogen peroxide can rid fresh fruits and vegetables of harmful bacteria such as Salmonella and E. coli; pasteurize dairy products; and sterilize paper food packages such as juice boxes, which eliminates the need for refrigeration.

To remove the hydrogen peroxide left over in wastewater after bleaching, some industrial chemists turn to a special type of enzyme called a catalase. Catalase enzymes, found in most living things, break down hydrogen peroxide into water and oxygen. This protects cells from oxidative stress -- the biological equivalent of rust.
But industrial waters can push enzymes to their limit. Most commercial catalase enzymes hail from organisms that prefer moderate temperatures, such as cows and fungi; high temperatures and high pH of industrial processes destroy these enzymes quickly.

Animals and people are designed to operate between 95 and 105 degrees Fahrenheit, any catalase derived from a mammal is not going to be stable at extreme conditions.

Catalase enzyme was isolated from T. brockianus and its industrial half-life was found to be 15 days instead of the 15 seconds of other catalase enzymes -- an 86,000-fold improvement. Scientists use an enzyme's half-life -- the amount of time it takes to lose half its effectiveness -- as a yardstick for comparing two enzymes.
Large-scale production of the T. brockianus enzyme could end decades of environmental costs from industrial bleaching. Chlorine, used for more than a century, forms toxic and carcinogenic chemicals called dioxins as byproducts. Industries switching to greener hydrogen peroxide have developed wastewater treatment options -- though all have come with extra cost or environmental problems.

One hydrogen peroxide treatment dilutes wastewater with pure water, but this drives up cost and produces even more waste. Another solution treats wastewater chemically with salts, but its harmful residue essentially cancels out the environmental benefits of using hydrogen peroxide in the first place.

The most direct wastewater treatment uses a catalase to break down hydrogen peroxide. But scientists working with commercial catalases have had to make a choice: either spends time and money bringing wastewater temperatures and pH down to tolerable levels, or else continually adds more catalase to untreated wastewater to replenish the enzyme.

With the T. brockianus extremozyme, hydrogen peroxide decomposes safely, and wastewater needs no extra pretreatment. What's more, the enzyme lasts long enough to treat multiple batches of wastewater.

I picked these bacteria because of its importance to chemical processing industries.

References:

• Alfredsson G. A. ; J. K. Kristjansson; S. Hjorleifsdottir; K. O. Stetter; 1988. Rhodothermus marinus, gen. nov., sp. nov., a thermophilic, halophilic bacterium from submarine hot springs in Iceland. J. Gen. Microbiol., vol. 134, pp. 299–306
• Huber, R., K. O. Stetter, The Prokaryotes: An Evolving Electronic Resource for the Mircobiological Community. 2004. Springer-Verlag New York, LLC.
• Pask-Hughes R. A. ; R. A. D. Williams; 1977. Yellow-pigmented strains of Thermus spp. from Icelandic hot springs. J. Gen. Microbiol., vol. 102, pp. 375–383
• Tangandro Expedition. 1996. "Tangandro." Institut de Génétique et Microbiologie.
• Williams, R. A. D., M. S. Da Costa, The Prokaryotes: An Evolving Electronic Resource for the Mircobiological Community. 2004.

*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.

 

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