The free- and protein-amino acids of the rumen phycomycete fungi Neocallimastix frontalis and Piromonas communis

SUMMARY The proteins and the amino acid profile of the rumen fungi Neocallimastix frontalis and Piromonas communis have been examined and the in vitro digestibility of the vegetative growth determined. The mean true protein content of N. frontalis was 24% of the dry weight and 30% for P. communis, which has a lower chitin content. 50% of the protein extracted from cells and examined by HPLC was in the 200000 MW range and 40% in the 50000 MW range. Polyacrylamide gel electrophoresis after treatment with sodium dodecylsulphate and 2-mercaptoethanol indicated that the native proteins were composed of smaller units in the MW range 25000–50000. The amino acid profiles of the two fungi were similar and compared favourably with those of casein and fraction 1 protein of lucerne.