[Nutritional study of the membranes of Saccharomyces cerevisiae. 2. Utilization by the rat]

The proteins of the membranes have a digestibility of 95%. As their content of lysine and threonine is high, they effectively supplement a diet with wheat gluten. When they are added up with methionine, their efficiency is comparable with that of casein. The carbohydrates of membranes are really different from cellulose and from the indigestible matter of plants, in both chemical and physiological fields: a) they are degraded in the caecum by the microorganisms; b) they do not decrease the digestibility of the ration. However, their true interest for the non-ruminant species remains uncertain and their true digestibility is difficult to calculate. According to some indirect criterions, it might be situated about 80%. The lipids of membranes have a digestibility of 35%. This fact must not be due to the nature of the fatty acids, but may be attributed to the very strong fixation of lipids in the membranes which makes their extraction by the solvents very difficult. Finally, the membranes of S. cerevisiae may be considered as a food product, mainly because of the efficacy of their proteins.