STUDIES ON THE FERMENTATION OF SORBITOL BY ORAL MICROORGANISMS

¹ University of Maryland, School of Dentistry, Baltimore, Md.

1. An attempt is described to make a quantitative estimation of the number of individuals whose saliva contains sorbitol-fermenting microorganisms, and the percentage of sorbitol-fermenters in the saliva. The technical difficulties involved in such a procedure probably invalidated the results obtained.

2. By inoculating 122 samples of saliva in nutrient broth or Trypticase broth containing M/10 concentrations of sorbitol, dextrose, and sucrose; the pH and titratable acidity developing in these cultures incubated for 24 hours. at 37°C. under aerobic conditions were determined. Sorbitol was fermented much more slowly than either of the other sugars and seldom reached a pH of 5.0.

3. Fifty-five samples of saliva were incubated in a modified Brewer's thioglycollate medium for anaerobic cultivation and the developing pH values determined. Sorbitol, sucrose, and dextrose in M/10 concentrations were placed in this medium and the sorbitol was found to be fermented much more slowly than the other sugars.

4. Strains of L. acidophilus, oral streptococci, yeasts, and mixtures of yeasts and L. acidophilus were inoculated into Trypticase broth containing M/10 concentrations of sorbitol, dextrose, and sucrose. These test organisms were also inoculated into a modified thioglycollate medium containing M/10 concentrations of the above sugars. In all cases sorbitol was fermented more slowly than the other sugars.

5. The practicability of employing sorbitol as a substitute for sucrose or dextrose in the sweetening of foods, beverages, confections, etc. is discussed. On the basis of these in vitro studies, it is suggested that in view of the slow fermentation of sorbitol it might be useful in the prevention or control of dental caries. The cause of the delayed fermentation of sorbitol is discussed.