PureMash system provides antibiotic free antimicrobial solution

By Jerry W. Kram | April 08, 2008
Web exclusive posted April 21, 2008 at 11:47 a.m. CST

To produce ethanol, producers must create a pleasant environment for a living creature, yeast, which does the heavy lifting of converting sugars to alcohol. Unfortunately, other organisms also find the inside of a fermentation tank to be hospitable and compete with - and inhibit - the growth of yeast, lowering an ethanol producer's efficiency and production. To combat the growth of bacterial invaders such as Lactobacillus and Acetobacter, which produce organic acids that inhibit ethanol production, facilities have resorted to dosing their tanks with antibiotics. However, this has been a short term fix - tanks can become reinfected and the antibiotic leaves residues in the distillers grains, causing concerns with some feedlot operators.

PureMash is a system developed by Resonant Biosciences LLC which greatly reduces bacterial contamination in ethanol plants without leaving antibiotic residues in the distillers grains, says company president Allen Ziegler. The system is based on a water purification technology which uses chlorine dioxide (ClO2) and hydrogen peroxide to kill bacteria. Yeast turned out to be resistant to the chemicals' antiseptic properties. "We came across this technology a few years ago when I was working for Miller Brewing," Ziegler said. "When they went to aseptic brewing they started having all kinds of infection problems. We found that yeast could stand up to the chemicals to a very high degree where the other microbes could not. We also found [the chemicals] can stand up to a high organic matrix."

Because ClO2 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. ClO2 also attacks biofilms which 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, which are more resistant to antibiotics and antiseptics, can be a source of reinfection in an ethanol fermentation tank. "Because of production reasons, ethanol plants don't go through the levels of cleaning you find in a brewery, so they wind up leaving lots of biofilm in the heat exchangers," he continued. "When we directed our technology to the heat exchanger and then the fermenter, we were able to clean up that heat exchanger and a lot of source of the infection."

PureMash is integrated into a facility's distributed control system allowing full control and monitoring of the process. It also provides data tracking, allowing plant operators to investigate when a problem arises. "It helps you run the plant too," Ziegler said. "From an engineering and operations standpoint, it really lets you look to see where you have any issues in real time. So it is really like looking at a whole other way of running and operating a plant while dealing with unwanted microbiology."

During the summer of 2007, Resonant Biosciences tested the process in a healthy ethanol plant in Montreal. It then tested the system in facilities that had bacterial contamination problems, some of which had recurring problems for several years. The results were dramatic. "The plant we went into gave us their worst fermenter," Ziegler said. "It had [organic acid levels] a good 30 to 40 percent higher than the other three fermenters. In a period of just three fermentations, we took that fermenter that was notorious over the last three or four years and got its [organic acids] down to 30 percent lower than the other three fermenters. They had spent years and a lot of money trying to address the problem. We were able to do it in one week."

The company is conducting tests in plants with minimal bacterial contamination problems to confirm the system's ability to increase ethanol production in clean plants. "The first plant we went into had some mild infections and we were able to demonstrate significant ethanol gains," Ziegler said. "Even in the lab in experiments with no organic acids present we're seeing an ethanol gain."

With the positive test results, PureMash received U.S. Environmental Protection Agency's registration in February and is now commercially available through Ethanol Technology of Milwaukee, Wisc. Ten plants have signed up to have the system installed. Ziegler said the system is available through a leasing arrangement with monthly payments that are similar in cost to what many plants pay for antibiotics. "The plants we are going into, we are matching their antibiotic pricing," he said. "But [the plants] are showing higher ethanol production and much less variation in ethanol production. 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."

An added benefit of the PureMash system is that the only traces of chemical left in the distillers grains is in the form of chloride, which is a component of common table salt. The level of chloride left in the mash is well within the acceptable limits set by federal regulations - and that allows companies using the PureMash system to sell their distillers grains as antibiotic free. Ziegler said the companies using the system are receiving a premium in the marketplace for distillers grain. "That seems to be one of the primary drivers of interest in the system," he said. "

Resonant BioSciences are partnering with Ethanol Technology to commercialize and distribute the PureMash technology.