SIMPLE RELATIONSHIP BETWEEN ACID DISSOCIATION-CONSTANT AND MINIMAL PHFOR MICROBIAL-GROWTH IN LABORATORY MEDIUM

A simple relationship was observed in growth medium, between the disso ciation constant (via the pK(a)) of the acid used to control pH and th e 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. Thi s method, illustrated on Listeria monocytogenes, would merely require the knowledge of two minimum pH values, one for a strong acid (e.g. hy drochloric acid) and one for a weak acid (e.g. acetic or propionic aci d). From these two values, It seems possible to estimate for a given g rowth medium, the minimum pH value for any other acid within the defin ed pK(a) range. (C) 1997 Elsevier Science B.V.