Reduction of invasive bacteria in ethanol fermentations using bacteriophages

Abstract

Invasive Lactobacillus bacteria inhibit ethanol fermentations and reduce final product yields. Due to the emergence of antibiotic resistant strains of Lactobacillus spp., alternative disinfection strategies are needed for ethanol fermentations. The feasibility of using the bacteriophage (phage) 8014-B2 to control Lactobacillus plantarum in ethanol fermentations by Saccharomyces cerevisiae was investigated. In 48 h media-based shake flask fermentations, phages achieved greater than 3-log inactivation of L. plantarum, protected final ethanol yields, and maintained yeast viability. The phage-based bacterial disinfection rates depended on both the initial phage and bacterial concentrations. Furthermore, a simple set of kinetic equations was used to model the yeast, bacteria, phage, reducing sugars, and ethanol concentrations over the course of 48 h, and the various kinetic parameters were determined. Taken together, these results demonstrate the applicability of phages to reduce L. plantarum contamination and to protect final product yields in media-based fermentations.

Adaptation to low pH and lignocellulosic inhibitors resulting in ethanolic fermentation and growth of Saccharomyces cerevisiae

“…Several attempts have been made to study and control bacterial contamination in lignocellulosic ethanol production including: (1) adding NaCl and ethanol to wood hydrolysate (Albers et al 2011), (2) high solid loading in simultaneous saccharification and fermentation (SSF) (Ishola et al 2013), (3) usage of an antibiotic like gentamicin and biomass autoclaving (Serate et al 2015), and (4) usage of bacteriophages (Worley-Morse et al 2015). These strategies encounter challenges including: (1) additional cost and need for extensive fine tuning and testing of concentrations of NaCl and ethanol (Albers et al 2011), (2) loss of cell viability due to mechanical stress caused by solid particles in high cell loading (Ishola et al 2013), (3) cost and environmental challenges posed by gentamicin, energy expenditure and formation of inhibitors due to autoclaving (Serate et al 2015), and (4) rise of bacteriophage-insensitive mutants and possibilities of gene transfer from bacteriophages to yeast (Worley-Morse et al 2015). One of the potentially scalable and economically feasible solutions to control bacterial contamination is to run the lignocellulosic fermentation at low pH, around pH 4 where the growth and viability of bacteria are drastically reduced (Kádár et al 2007).…”

Bacterial contamination and xylose consumption during ethanol production by "Saccharomyces cerevisiae" Contaminação bacteriana e consumo de xilose durante a produção de etanol por "Saccharomyces cerevisiae"

“…Therefore, endolysin is a general term used to describe Contamination control using endolysins in ethanolic fermentations was already proved efficient at a laboratory level by Roach and collaborators (2014). In addition, a recent work described a methodology that consists in the use of live bacteriophages to control Lactobacillus populations in ethanolic fermentations (Worley-morse et al, 2015). These works corroborate with the idea that endolysins can be potential substitutes for traditional antibiotic use in ethanolic fermentations.…”

Modelling Phage−Bacteria Interaction in Micro‐Bioreactors

“…The plate reader also enabled frequent OD measurements ( e.g ., every 30 min), stable temperature (30°C), and constant shaking without any interruptions. The use of this method, however, did not allow monitoring substrate and phage concentrations as done by Santos et al and Worley–Morse et al . This made the calibration process entirely dependent on changes in the total bacterial population.…”