Effect of yeast inoculation rate on the metabolism of contaminating lactobacilli during fermentation of corn mash

Abstract Two separate 4 (bacterial concentrations)×6 (yeast concentrations) full factorial experiments were conducted in an attempt to identify a novel approach to minimize the effects caused by bacterial contamination during industrial production of ethanol from corn. Lactobacillus plantarum and Lactobacillus paracasei, commonly occurring bacterial contaminants in ethanol plants, were used in separate fermentation experiments conducted in duplicate using an industrial strain of Saccharomyces cerevisiae, Allyeast Superstart. Bacterial concentrations were 0, 1×106, 1×107 and 1×108 cells/ml mash. Yeast concentrations were 0, 1×106, 1×107, 2×107, 3×107, and 4×107 cells/ml mash. An increased yeast inoculation rate of 3×107 cells/ml resulted in a greater than 80% decrease (P