Short communication: Combined antimicrobial activity of reuterin and diacetyl against foodborne pathogens

Abstract

Reuterin (β-hydroxypropionialdehyde) is a broad-spectrum antimicrobial substance produced by some strains of Lactobacillus reuteri during anaerobic fermentation of glycerol. Some of these strains are able to survive and produce reuterin in cheese and yogurt when added as adjuncts to the starter. Similarly, in fermented dairy foods, other inhibitory compounds such as lactic acid and diacetyl are produced during fermentation. In this work, we studied the combined effect of reuterin and diacetyl under different pH conditions against Escherichia coli O157:H7, Salmonella Enteritidis, and Listeria monocytogenes. Results from agar spot assays showed that the antimicrobial activity of reuterin-producing strains against the gram-negative bacteria tested was enhanced as the concentration of diacetyl increased to 50 mg/kg, and was higher under acidic conditions (pH 5.0) for the 3 pathogenic strains. The combination of reuterin and diacetyl had an additive effect against L. monocytogenes only at diacetyl concentrations of 50 mg/kg and pH 5.0. In addition, growth kinetics studies showed that the combination of 1 activity unit (AU)/mL of reuterin with 100mg/kg diacetyl increased the lag time of the 3 pathogens. In milk, synergistic antimicrobial activity was observed with the combination of 1 AU/mL reuterin and 50 or 100 mg/kg of diacetyl on the gram-negative strains tested, and with 1 AU/mL reuterin and 100 mg/kg of diacetyl on L. monocytogenes. The greatest inhibition of the 3 pathogens was achieved in acidified milk at pH 5.0 with reuterin (1 AU/mL) and diacetyl (100 mg/kg). Based on these results, the combination of reuterin and diacetyl in acidified dairy products could be a promising strategy to control food pathogens in these products.

Identification and quantification of antifungal compounds produced by lactic acid bacteria and propionibacteria

“…Concerning reuterin, corresponding to a mixture of monomeric, hydrated monomeric and cyclic dimeric forms of 3-hydroxypropionaldehyde (Talarico and Dobrogosz, 1989), this compound has been shown to be a broad-spectrum antimicrobial substance (Cleusix et al, 2007;Langa et al, 2014). However, in the tested conditions, reuterin was not detected in any of the antifungal supernatants, including that of L. reuteri 5529.…”

Models of toxicity of diacetyl and alternative diones

“…The 1980’s and early 1990’s saw the isolation and characterization of diacetyl reductase that converts DA to acetoin, while analytic methods for the detection of DA and its derivatives improved. In 1996, Sengupta et al (Sengupta, Chou et al 1996) identified a DA-specific odorant receptor in C. elegans that is used to affect chemotaxis towards or away from food sources (Langa, Martin-Cabrejas et al 2014). Notably, Linda Buck who first cloned this family of receptors in 1991 (Buck and Axel 1991) was awarded the Nobel Prize in Physiology or Medicine for this fundamental observation.…”

Strain-to-strain differences within lactic and propionic acid bacteria species strongly impact the properties of cheese–A review

“…Such a synergistic effect of diacetyl and reuterin, a bacteriocin produced by some Lactobacillus reuteri strains, was recently demonstrated against several foodborne pathogens (E. coli O157:H7, Listeria monocytogenes, and Salmonella enterica subsp. enterica serovar Enteritidis (Langa et al 2014)). …”