Abstract
A broad-spectrum reuterin produced during anaerobic fermentation of glycerol by Lactobacillus reuteri strain 12002 was found to be inhibitory and bactericidal for Listeria monocytogenes and Escherichia coli O157:H7. Lyophilized reuterin was prepared by a two-step fermentation process. A batch fermentation in a 15-liter fermentor was applied to produce a maximum biomass of L. reuteri using a modified MRS broth at pH 4.3. Further, harvested cells were used to ferment glycerol (250 mM) under anaerobic conditions. The sensitivity to reuterin of 10 strains of Listeria spp., including 6 strains of L. monocytogenes, and 6 strains of E. coli, including one enterotoxigenic E. coli strain and two enterohemorrhagic E. coli strains, was estimated. Strains of L. monocytogenes were more resistant to reuterin than E. coli strains. In cottage cheese, pH 5.4, L. monocytogenes increased by 0.4 log while E. coli O157:H7 decreased by 0.5 log in 21 days at 7°C; addition of reuterin (50 to 250 units per g) to the cottage cheese reduced the viability of both organisms. The inactivation rate was more pronounced (P ≤ 0.05) with E. coli O157:H7 than L. monocytogenes and it was dependent on reuterin concentration. The rate of E. coli O157:H7 population reduction reached to 2, 3, and 6 log cycles by day 7 for reuterin concentrations of 50, 100, and 150 units per g of creamed cottage cheese, respectively. While, 100, 150, and 250 units of reuterin per g caused reductions in L. monocytogenes counts by 2, 5, and greater than 5 log cycles, respectively. In UHT skim milk with 150 units of reuterin per ml, stored at 7°C, the decline in the numbers of L. monocytogenes cells was higher than that in cottage cheese. Milk fat in the range of 0.5 to 3% did not affect the reuterin activity (P ≤ 0.05). Addition of 3% salt enhanced the lethal effect of reuterin and diminished the initial population of L. monocytogenes by 4.5 log cycles in three days at 7°C.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.