Transgenic Saccharomyces cerevisiae Reduces Lactobacillus Contamination during Fermentation

Lactobacillus species are the predominant contaminants during fermentation that decrease the profitability of biofuel production. Current antibiotic treatments against these contaminants have led to emergence of drug-resistant bacterial strains. Researchers from the National Center for Agricultural Utilization Research Service of the US Department of Agriculture in Peoria, Il, led by Piyum A. Khatibi published the result of their studies on a new, non-antibiotic, eco-friendly strategy against bacterial contamination.

Two genes, LysA and LysA2, from bacteriophage were individually expressed in Saccharomyces cerevisiae. These genes produce enzymes that are capable of breaking down common Lactobacillus species that contaminate fermentation. Reductions in Lactobacillus population in the infected fermentations with yeast expressing LysA or LysA2 were observed in just under 72 hours. Lactic acid and acetic acid levels were also reduced in all infected fermentations suggesting less contamination in fermentations with transgenic S. cerevisiae compared to those with untransformed yeast.

These results demonstrate the feasibility of using yeast expressing bacteriophage endolysins to reduce L. fermentum contamination during fuel ethanol fermentations.