Microbes make bleaching greener

Hydrogen peroxide is used widely in industrial bleaching processes, but until recently there were only a few options to handle process waste water in an environmentally-friendly fashion.

One option is to chemically treat the water to break hydrogen peroxide down, but that practically cancels out the environmental benefit. Or, the water can be heavily diluted with even more water, but that increases the volume of the waste water. Using catalase enzymes to break down hydrogen peroxide into water and oxygen is a good alternative, but commercially available enzymes require cool wastewater temperatures and lower pH conditions. Wastewater, of course, is typically hot and alkaline and hence unfriendly to these enzymes.

Now, chemical engineer Vicki Thompson and biologists William Apel and Kastli Schaller from the US Department of Energy's Idaho National Engineering and Environmental Laboratory (INEEL) may have the answer. They have discovered that an enzyme taken from a microbe that thrives in the depths of a Yellowstone National Park hot springs pool might just be the key to transforming industrial bleaching from environmentally problematic to environmentally green.

The new catalase enzyme, from a Thermus brockianus microbe likes extreme conditions - performing best at temperatures around 90 degrees Celsius (194 degrees Fahrenheit) and in highly alkaline pH of more than 9. In laboratory tests, it functioned well for as long as 360 hours under these conditions compared to a mere 15 to 20 minutes for other commercially available catalases.

For the T. brockianus catalase, breaking down hydrogen peroxide in an industrial setting is just another day at the office. Within a microorganism, the enzyme's normal role is to break down hydrogen peroxide that is naturally produced by cellular activity. This protects cells from oxidative stress - the biological equivalent of rust.

The next step for the research team is to find a way to produce the enzyme in high volume. That means identifying the gene that encodes the T. brockianus catalase and inserting it into a microbe that is easily grown in large quantities. Then, researchers can use already established technology to attach the enzyme to tiny polymer beads and pack them into columns that will filter industrial wastewater.

The research team is currently discussing the industrial possibilities of this catalase with a major hydrogen peroxide manufacturer.