Simple relationship between acid dissociation constant and minimal pH for microbial growth in laboratory medium

Abstract

A simple relationship was observed in growth medium, between the dissociation constant (via the pK(a)) of the acid used to control pH and the minimum pH at which Salmonellae and Escherichia coli initiate growth. From this new relationship, a simple method was proposed to predict the minimum growth pH for a given strain and different acid types. This method, illustrated on Listeria monocytogenes, would merely require the knowledge of two minimum pH values, one for a strong acid (e.g. hydrochloric acid) and one for a weak acid (e.g. acetic or propionic acid). From these two values, it seems possible to estimate for a given growth medium, the minimum pH value for any other acid within the defined pK(a) range.