Nutritional availability of amino acids from the rumen anaerobic fungusNeocallimastixsp. LM1 in sheep

Abstract

SUMMARYThe rumen anaerobic fungusNeocallimastixsp. LM1 was specifically labelled in batch culture with either [14C]lysine, [14C]lysine + [3H] tyrosine, [14C] methionine, or [35S] sulphide. Fractionation of acid hydrolysates of fungal biomass on an amino acid analyser showed that the labelled amino acids were directly incorporated into fungal protein with little or no degradation. [35S] Sulphide was incorporated into cysteine and methionine.Absorption of amino acids from the small intestine was measured in sheep with permanent fistulae in the abomasum and terminal ileum, by introducing radiolabelled fungal biomass into the abomasum together with Cr-EDTA as the marker for digesta flow. The proportions of [14C] lysine (Expt 1), [14C] lysine + [3H] tyrosine (Expt 2), [14C] methionine (Expt 3) and the sulphur amino acids from [35S] sulphide (Expt 4) which appeared unabsorbed at the terminal ileum averaged 0·13, 0·07 + 0·08, 0·13 and 0·02, respectively. These proportions reflect the high digestibility of certain essential amino acids and the sulphur amino acids of fungal proteins. The results indicate that the true fractional digestibility of fungal proteins isc. 0·9. Consequently, a large biomass of anaerobic fungi in rumen digesta would be expected to provide a valuable source of digestible amino acids to ruminants.

Anaerobic fungi (phylumNeocallimastigomycota): advances in understanding their taxonomy, life cycle, ecology, role and biotechnological potential

“…Anaerobic fungal proteases provide amino acids for fungal growth, as well as aiding the penetration of plant material. In addition to producing enzymes, anaerobic fungi themselves contribute to the protein supply of the host by serving as a source of high‐quality microbial protein, that is synthesised in the rumen, passing to the abomasum and intestines for subsequent digestion and absorption by the host (Kemp et al ., ; Gulati et al ., ; Atasoglu & Wallace, ).…”

Anaerobic Fungi: Past, Present, and Future

“…Besides producing proteases, AF directly contribute to protein supply of the host in terms of being part of the microbial biomass that passes down to the intestines from rumen, for subsequent digestion and absorption. Gulati et al (1989) showed that AF cells were composed of proteins with a well-balanced combination of amino acids that were highly available to the ruminant host. A high proportion of the protein components of three monocentric AF (i.e., Neocallimastix sp.…”

Effects of amino acids on the growth of an anaerobic rumen fungus Neocallimastix sp N 13

“…They are characterized by a high lysine content as compared with rumen bacterial proteins (Onoda et al, 1993). Moreover, fresh rumen fungi infused into the abomasum are extensively digested (Gulati et al, 1989). These findings suggest that the rumen fungi may substantially contribute to the amino acid supply for their host animals if notable amounts of fungi are transferred from the rumen to the lower gut.…”

“…Orpin and Greenwood (1986) demonstrated that amino acid supplements to the defined minimal medium (consisting of ammonium ion, haemin, vitamins and a reduced source of sulphur) greatly stimulate the growth of Neocallimastix patriciarum. The rumen fungi Neocallimastix sp can take up amino acids and incorporate them into proteins without requiring any modification of the amino acids (Gulati et al, 1989). When a mixture of L-(U-!4C) amino acids was added to cultures of rumen fungi, the radioactivity was later found located in the cellular proteins, lactate, volatile fatty acids and ethanol (Marounek and Vovk, 1992 (1989,1992) (1981) for 3 days and then zoospores were harvested anaerobically by filtrating the cultures through nylon meshes (10 0 pm).…”

“…The (fig 10). The other supplement consisting of Glu, Met and Ser (GMS), each of which has proven to be a significant growth stimulator for Neocallimastix patriciarum (Orpin and Greenwood, 1986) (Gulati et al, 1989 (fig 1 ).…”