Chemical inhibition of the contaminant Lactobacillus fermentum from distilleries producing fuel bioethanol

Abstract

The purpose of this study was to determine the Mini mum Inhibitory Concentration (MIC) of pure or mixed chemicals for Saccharomyces cerevisiae and Lactobacillus fermentum in the samples isolated from distilleries with serious bacterial contamination problems. The bioci des, which showed the best results were: 3,4,4’ trichlorocarbanilide (TCC), tested at pH 4.0 (MIC = 3.12 mg/l), TCC with benzethonium chloride (CBe) a t pH 6.0 (MIC = 3.12 mg/l) and TCC mixed with benzalkonium c hloride (CBa) at pH 6.0 (MIC = 1.53 mg /l). If CBa was used in sugar cane milling in 1:1 ratio with TCC, a 8 times reduction of CBa was possible. This formul ation also should be tested in fermentation steps since it was more difficult for the bacterium to develop resist ance to biocide. There was no inhibition of S. cerevisiae and there were only antibiotics as an option to ba cterial control of fuel ethanol fermentation by S. cerevisiae.