Toxicity of Intestinal Volatile Fatty Acids for Yeast and Esch. Coli

Abstract

The present investigation is one of a series aimed to throw some further light on the mechanisms involved in the destruction of microorganisms in the gastro-intestinal tract. In a previous investigation1 the fate of ingested live yeast in the stomach and small intestines was considered and it was found that considerable live yeast might escape destruction in these organs, only to be killed in the large intestines. It was of interest to try to determine what factors were responsible for the killing of micro-organisms in the large intestines. The present investigation deals first with attempts at the chemical isolation and identification of the substances present in the large intestines which are most toxic for yeast and other organisms. As a result of these experiments the volatile fatty acids appeared to be of importance. The second part of the paper attempts to determine the toxicity of the different volatile fatty acids through the ranges of concentration and of pH which may be found in the intestines, more information than at present available being necessary for the interpretation of analytical findings on intestinal contents. These results are also of interest in connection with other fermentation mixtures. In later communications the influence of diet on the intestinal volatile fatty acids and concomitant changes in flora will be dealt with more fully.