Low-concentration Sorbic Acid Promotes the Induction of Escherichia coli into a Viable but Nonculturable State

Abstract

　The effect of food preservatives and sanitizers at low concentrations on the induction of Escherichia coli into a viable but nonculturable (VBNC) state was investigated. When E. coli was incubated in physiological saline at 37℃, the viable cell count measured by plate counting was approximately 3-logs lower than that measured by flow cytometry after 30 days. This difference, and morphological changes in cells, confirmed the transition of E. coli into a VBNC state. Adding 10 μg/l of sorbic acid significantly promoted the induction of E. coli into a VBNC state. This effect was not seen with benzoic acid or sodium hypochlorite at the same concentration. Resuscitation of E. coli VBNC cells was successful when they were grown in nutrient broth containing sodium pyruvate. These results suggest that the presence of low concentrations of food additives in a food manufacturing environment may act as potential triggers for bacterial VBNC induction.