Killing bad bugs without residues

By Jerry W. Kram | June 02, 2008
PureMash, a system developed by Resonant Biosciences LLC, greatly reduces bacterial contamination in ethanol plants without leaving antibiotic residues in the distillers grains, said company President Allen Ziegler.

The system is based on a water-purification technology that uses chlorine dioxide and hydrogen peroxide to kill bacteria. Yeast are resistant to the chemicals' antiseptic properties.

Because chlorine dioxide doesn't react with organics such as starch and sugar or compounds such as ammonia like pure chlorine does, it can be used directly in the fermentation process. Chlorine dioxide also attacks biofilms that coat the insides of tanks, pipes and other equipment. "Where we found most of the infections coming from in these plants is actually the heat exchangers," Ziegler said. "A lot of the antibiotics will not get [those infection sources]." Bacteria in the biofilms are more resistant to antibiotics and antiseptics, and can be a source of reinfection in an ethanol fermentation tank.

The system is integrated into a plant's distributed control system, allowing full control and monitoring of the process. That also gives the plant a paper trail to review if needed
Testing in several ethanol plants showed the system was successful, and PureMash received registration from the U.S. EPA in February. PureMash is now commercially available through Ethanol Technology in Milwaukee. Ten ethanol plants have signed up to have the system installed. Ziegler said the system is available through a leasing arrangement with monthly payments that are approximately the same as many plants pay for antibiotics. "We are matching their antibiotic pricing, but [the plants] are showing higher ethanol production and much less variation in ethanol production," he said. "They don't see the wild swings in ethanol production anymore. With a little more history under our belt, I think we will be able to put a better number on the real cost of our system, but we should be right in the middle of what an average plant spends on antibiotics."