Paper
Combination of natural antimicrobials for contamination control in ethanol production
Published Oct 1, 2019 · J. Corrêa, F. Luciano, Natalia Janaina Lago Maia
World Journal of Microbiology and Biotechnology
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Abstract
AbstractPresence of bacterial contaminants at levels > 10^7 colony forming units per milliliter (CFU/mL) during ethanol production processes reduces the alcoholic fermentation yield by 30%. Antibiotics are currently used to control contamination, but their residues may be detected in yeast extract, restricting this by-product trade to several countries. Thus, the objective of this study was to assess antimicrobial activity of the natural compounds hops extract, 4-hydroxybenzoic acid, nisin Z, and lysozyme against Lactobacillus fermentum, Leuconostoc mesenteroides, and Saccharomyces cerevisiae, aiming development of a formula. Minimum Inhibitory Concentration of each antimicrobial was determined for bacteria and subsequently, nisin (30 mg/L) and hops extract (5 mg/L) were tested together, showing inhibitory effects combining doses of each antimicrobial that were equivalent to an eightfold reduction of their original Minimum Inhibitory Concentrations (3.75 and 0.625 mg/L, respectively), resulting in a FIC_Index of 0.25. Thereon, a formula containing both compounds was developed and tested in fermentation assays, promoting reductions on bacterial population and no severe interferences in yeast viability or population even at extreme doses. Therefore, these compounds have great potential to successfully substitute conventional antibiotics in the ethanol industry.Graphic abstract
In Vitro StudyA formula combining nisin and hops extract effectively reduces bacterial contamination in ethanol production without affecting yeast viability or population, making it a potential substitute for conventional antibiotics in the ethanol industry.
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