USDA Agricultural Research Service (ARS) scientists have developed a way to use genetically modified baker’s yeast to prevent contamination by unwelcome bacteria in ethanol plants, one of the leading causes of plant shut downs.

“These bacteria are found everywhere in the environment, especially on plant material. They are actually responsible for the fermentation of vegetables to make products like sauerkraut and pickles,” explained Shao-Yeh Lu, a research microbiologist with ARS’ National Center for Agricultural Utilization Research in Peoria, Illinois. “Unfortunately, the acetic acid and lactic acid produced by these same bacteria in a bioethanol fermentation facility will cause stress and inhibit the growth of the baker’s yeast (Saccharomyces cerevisiae), which is responsible for the production of ethanol.”

Instead of using antibiotics to kill the bacteria, the scientists modified the yeast’s genetic makeup with to make an enzyme on its outer surface called endolysin, a specialized enzyme that kills the bacteria on contact. Lab trials found use of the endolysin-making yeasts reduced the presence of the bacteria by 85 percent, which reduced acetic and lactic acid levels in the mash by as much as 40 percent and 71 percent, and in turn increased ethanol production by as much as 40 percent.

According to Lu, modifying yeast to produce endolysin—either on their surface or secreted—is likely to be more cost-effective than adding bulk amounts of the enzyme to contaminated corn mash. Additional research is needed to fully ascertain its potential commercial use, but if validated through larger-scale trials, the endolysin-wielding yeasts could offer an alternative to antibiotics or other costly chemical cleansers.