Abstract
The nutritive values of the protein produced free from the yeast cells (Trichosporan sp. X-19) in acidic cultural condition (pH 3.0) were examined by both in vitro digestion tests and rat feeding trials. The results obtained were as follows:
1) In vitro digestibilities of the ECP by two enzymes, pepsin and trypsin, were similar to those of casein.
2) Compared to the essential amino acid scoring pattern published by FAO/WHO (1973), the ECP was found to be lower in sulfur-containing amino acids, which were the first limiting amino acid. The amino acid score was calculated to be 45.
3) Protein efficiency ratios (PERs) of the ECP at 10 and 25% protein levels were 0.32 and 0.90, respectively, and were much lower than those of casein (2.68 and 1.38). By adding 0.5% of L-methio-nine to the ECP-containing diets, however, PERs increased to the values almost equal to those of casein.
4) Though the true digestibility of the ECP was comparable to that of casein, biological value (BV) and net protein utilization (NPU) were much lower than those of casein. However, both BV and NPU became similar to those of casein by the supplementation of methionine.
