Effect of sodium benzoate upon certain yeasts.

Abstract

The data collected under the conditions of these experiments indicate a marked difference in resistance of pure yeasts to sodium benzoate. On dextrose agar and in dextrose broth even in the presence of 0.40 per cent of sodium benzoate, growth was appreciable. Torla communis did not grow after the concentration of the benzoate in the broth had reached 0.15 per cent. One strain of Sacch. ellipsoideus was also inhibited at this concentration. Another strain showed a greater resistance; it grew in the presence of even 1 per cent but the growth was slower and less abundant. The fungi used seemed to be able to tolerate the sodium benzoate better when growing on a solid medium containing it than when growing in a liquid medium. This is probably explained by the fact that on the solid medium the organisms may use up the disinfectant during the early stages of growth so that the cells which develop later in the history of the culture do not have to endure such a high concentration as in the beginning. In liquid media such as dextrose broth, the sodium benzoate is in solution and therefore may come into closer contact with the cells. Two of the strains of budding fungi, Mycoderma uini and a pure culture from vinegar (No. 18) were able to grow apparently as well in the presence of one per cent of sodium benzoate as in the controls.

In sterilized apple juice the results were more striking. The sterile apple juice was almost as good a medium for the yeasts as the sterile dextrose broth since in the control tubes without any preservative the growth was abundant. However, when sodium benzoate was added the growth was markedly inhibited since none of the fungi grew after 0.01 per cent had been added.