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5). The enzymes of the pathway are inducible, and their synthesis is elicited by primary substrates or metabolic intermediates in the pathway. In a taxonomic study, Moscoso-Vizcarra and Popoff (1977) found that Enterobacteriaceae could be divided into two groups with respect to benzoic acid metabolism. In the first group, benzoate could be metabolized through the β-ketoadipate pathway; the second group consisted of those organisms that did not metabolize benzoate. Thayer and Wheelis (1976) characterized an inducible benzoate permease system involved in the uptake of benzoate by cells of Pseudomonas putida.

Rouxii No. of Strains Tested pH 2 pH 3 pH 5 pH 7 3 1 5 1 2 2 4 4 6 2 NG — — — — NG NG — NG NG — — 250 — — — — — 250 — 500 250 1200 500 750 750 500 750 1200 750 1200 1200 1200 1200 1200 1200 1200 1200 NG 1200 Note: NG, no growth in the absence of benzoic acid; — no growth in the presence of 250 mg of benzoic acid/L. Source: Adapted from Praphailong and Fleet (1997). The effects of benzoic acid were studied in the preservative-resistant yeast Z. bailii (Warth, 1991a). At concentrations up to 4 mM, fermentation was stimulated and low levels of benzoate were accumulated.

This method was based on finding the relative effectiveness of an inhibitor, like benzoic acid, at various concentrations. The relative effectiveness values of benzoic acid were established for S. bayanus and Hansenula species. 3). The x-axis intercept was the concentration of the inhibitor that gave infinite microbial inhibition. The infinite inhibition concentrations for S. bayanus and Hansenula species were 330 and 180 ppm benzoic acid, respectively, when these organisms were grown in Trypticase® soy broth.