Stimulatory and Inhibitory Effects of Protein Amino Acids on Growth Rate and Efficiency of Mixed Ruminal Bacteria

Abstract

Mixed ruminal bacteria were incubated in vitro with glucose, xylose, cellobiose, and various protein amino acids replaced isonitrogenously with 25% (i.e., 25 mg of N/L) of ammonia-N, to determine the growth rate and the amount of sugar consumed in the exponential growth phase. The growth rate and efficiency (grams of bacteria per gram of sugars) increased by 46 and 15%, respectively, when a mixture of 20 amino acids was added. On the other hand, neither growth rate nor efficiency increased when any one of these amino acids was added singly, except for Glu and Gln, each of which produced significant but small improvements. The stimulatory effect of the combined amino acids on bacterial growth declined when each of Leu, Trp, Tyr, Glu, Met, Phe, and Val was removed from the original group of 20. When a mixture of only these seven amino acids was used as a supplement, their stimulatory effects on growth rate and efficiency were only 21 and 25%, respectively, of the effects that the mixture of 20 amino acids showed. The effects increased to 76 and 72% on growth rate and efficiency, respectively, when Gly, Cys, and His were supplied in addition to the seven amino acids. The growth rate and efficiency of the ruminal bacteria were inhibited by an addition of each of Ile, Thr, Cys, Phe, Leu, Lys, or Val to ammonia-N, and the effects of the first five of these amino acids were highly significant. Isoleucine, threonine, and phenylalanine were each inhibitory even at a low concentration (1 mg of NL), while cysteine and leucine showed inhibitory effects at higher concentrations (more than 10 mg of N/L). A higher growth rate of the ruminal bacteria when supplemented with amino acid mixtures was accompanied with a higher growth efficiency, which was attributable to a relatively smaller proportion of energy expended on maintenance according to the Pirt derivation.

Does the addition of glutamine to enteral feeds affect patient mortality?*

“…Thus, when glutamine is administered enterally, multiple pathogens residing in the gastrointestinal tract have access to it and its benefits. The growth rate of mixed luminal bacteria, for example, was found to increase when exposed to high levels of glutamine (24). This theory may also explain why parenteral glutamine supplementation has been shown more definitively to have a positive effect on mortality rate as the glutamine is not being introduced directly to the bacteria in the gut flora.…”

“…Some studies have supported the use of enteral glutamine (2,13,14), primarily for reduction in infectious morbidity (15)(16)(17)(18), whereas others have found no benefit or conflicting results (19 -22). Some authors warn of potential harm (23), and animal studies have demonstrated an increased growth rate of bacteria when incubated in the presence of glutamine (24). The results of studies evaluating the role of parenteral glutamine show a trend toward improved outcomes (2-4, 9, 14).…”

Effects of aromatic amino acids, phenylacetate and phenylpropionate on fermentation of xylan by species of rumen anaerobic bacteria

“…Previous pure culture studies also showed AA being stimulatory to the growth yield of R. albus SY3 and R. flavefaciens 17 (Atasoglu et al, 2001). Also, several experiments conducted with mixed ruminal microorganisms confirm the stimulatory effects of AA on microbial growth (Argyle and Baldwin, 1989;Atasoglu et al, 1999;Kajikawa et al, 2002;Atasoglu et al, 2003).…”

“…However, aromatic AA have been known to limit the growth of microbes and xylan fermentation by mixed rumen micro-organisms (Kajikawa et al, 2002;Atasoglu et al, 2003;Guliye et al, 2005). Phenylalanine, one of the aromatic AA, has been suggested to be essential for the growth of cellulolytic bacterial species, including Ruminococcus (Allison 1965) and Fibrobacter succinogenes (Allison, 1965;Atasoglu et al, 2001).…”

Effects of aromatic amino acids, phenylacetate and phenylpropionate on fermentation of xylan by the rumen anaerobic fungi,Neocallimastix frontalisandPiromyces communis

“…1999). However, aromatic AA have been implicated to limit the growth of and fermentation by mixed rumen micro‐organisms (Kajikawa et al . 2002; Atasoglu et al .…”