Development of a complex antibacterial cocktail and its application in industrial fermentation processes

Abstract

One of the main problems encountered in alcoholic fermentation in industrial plants is related to sugars losses and increases in costs resulting from bacterial contamination by lactic acid bacteria of the genus Lactobacillus. Depending on the species of Lactobacillus, losses in ethanol production can reach 27%, increasing the cost of production due to both low yield and increased use of antibiotics. Contamination levels can reach 10 ^8 colony-forming units per ml causing negative impacts on fermentation, such as pH change due to lactic acid production, competition for sugars with process yeasts, in addition to flocculation, with major impacts on efficiency fermentation. The objective of this work is to develop a biological control process using wide variety of bacteriophages, as an alternative to antibiotics, to minimize the problem of bacterial contamination in alcoholic fermentation vats and/or other industrial processes. The advantages of phage treatment over antibiotics are: effectiveness against bacteria resistant to various drugs; ability to destroy only target bacteria, not altering the natural microbiota; it presents a fast response to the appearance of resistant mutant bacteria because the frequency of mutation of the phage is significantly higher than that of the bacteria; it has a lower development cost compared to a new antibiotic; and side effects are rare. As main results obtained through the PIPE project phase 1 (2017/08756-8), there is the creation of a bacterium collection, still small, containing more than 50 contaminating bacteria from the productive environment, isolation of more than 20 phages with lytic activity, and the construction of a cocktail of phages with action to control alcoholic fermentation on a laboratory scale that allowed to control the induced contamination bringing consistent gains in performance and yield, although there are points of clarification that will be solved during trials on a pilot scale and in partners, such as: effect of yeast recycling; effect of acid treatment; reduction of bacterial load; best stage of the application process; definition of maintenance applications; and shock dose. The creation of an efficient cocktail with a wide spectrum of antibacterial action will allow the replacement of the use of antibiotics in industrial processes, preventing the development of resistant microorganisms, the formation of bacterial biofilms on the wall of the fermentor (difficult to remove and which persist to be cleaned and often contaminate subsequent fermentation) and devaluation of co-products due to remnants of antibiotics. In addition, the use of a phage cocktail has great potential, as it has several new applications in the areas of medicine, human and animal food health and environmental decontamination. (AU)