A chemical and biological assessment of Aspergillus oryzae and other filamentous fungi as protein sources for simple stomached animals.

Abstract

AbstractA. oryzae had previously been selected as an organism suitable for a proposed farm fermentation system designed to improve the protein content of barley grain. Amino acid analyses and measurements of protein nutritive values in rats and pigs were carried out with A. oryzae grown on barley grain and potato substrates. For comparison, Fusarium semitectum, Trichoderma viride, Gliocladium deliquescens, Rhizopus arrhizus and a different strain of A. oryzae were also evaluated. There were small variations in the content of essential amino acids between the organisms studied. When referred to the requirements of the growing rat or pig, all species were deficient in the S‐amino acids which were generally the first limiting acids. In experiments with rats, the fungi gave net protein utilisation (NPU) values in the range 34 to 44; and true digestibilities ranged from 69 to 83%. Supplementation with L‐methionine gave a somewhat varied response with marked increases in NPU with some fungi (e.g. F. semitectum). In experiments with pigs, supplementation of A. oryzae with DL‐methionine did not give the expected increase in NPU and with one preparation (A. oryzae grown on barley) there was an apparent depression in NPU. The reason for this anomalous behaviour is not clear; and because under these experimental conditions F. semitectum behaved more predictably, it is suggested that nutritionally it is better suited to the farm process than A. oryzae. Non‐α‐amino N in the form of chitin (plus chitosan), nucleic acids and nucleotides accounted for between about 10 and 20% of the total N of the mycelia of these organisms.