THE PRODUCTION OF ACIDS FROM GLUCOSE BY ORAL MICROORGANISMS: LACTIC AND PYRUVIC ACIDS

¹ Department of Pharmacology and Therapeutics, New York University College of Dentistry, New York, N. Y., and Department of Biochemistry, Cornell University Medical College, New York, N. Y.

1. The action of oral microorganisms on glucose, in saliva as a medium and under physiologic conditions of temperature, CO₂ tension, and pH, has been studied for a variety of human beings, with respect to the rate and extent of action on glucose, the amount and type of acid produced, and the quantitative and temporal relation between glucose metabolism and acid production under these conditions.

2. Immediately upon contact between glucose and saliva, the microorganisms present initiate a rapid and sustained attack upon the glucose, so that in some instances as much as 80 per cent of the glucose added at a level of 0.13 per cent will disappear in 30 minutes.

3. One major result of the action of oral microorganisms on glucose is the production of lactic acid. However, for most subjects studied the lactic acid formed accounted for less than one-half of the total acid production as measured manometrically. Some pyruvic acid was occasionally formed, but in the majority of subjects lactic and pyruvic acid production did not account for more than one-half to two-thirds of the total acid production. The nature of the remaining acid or acids is not known.

4. In the mixed flora of the saliva, lactic and pyruvic acids are metabolized as well as produced. Hence, the net amount of acid present at any given time due to bacterial action on glucose represents a balance between rate of formation and rate of destruction.

5. Consideration of our results with respect to the presence or absence of active caries in the subjects studied failed to reveal any influence of this disease on the quantities measured.