Amino Acid Composition of Rumen Organisms
D. B. PURSER and SUZANNE M. BUECHLER
Institute of Nutrition and Food Technology, Ohio, State University, Columbus
Abstract
drolysi s. Total nitrogen was determined by the
Kjeldahl method.
The protozoal preparation was obtained in a
manner similar to that used for the preparation
of inoeula for protozoal cultures (9) and w a s
obtained from sheep fed a ration containing (in
per cent) alfalfa, 47, shelled corn, 42, ground
corncobs, 5, and molasses, 5.
Amino acid analyses were made of 22
strains of rumen bacteria grown in pure
culture. The organisms used were selected
to represent some of the predominant organisms found in the rumen when either
concentrates or roughages are fed. The
amino acid results expressed as grams per
100 g total amino acids showed very little
variation over the entire range of organisms
analyzed, thus supporting the hypothesis
that the amino acid composition of the
bacterial protein presented to the host for
digestion is relatively constant, irrespective
of the composition of the diet. These
amino acid distributions and the amino
acid distribution of a preparation of protozoal protein showed good agreement with
results of previous reports of analyses of
preparations of tureen microbial proteins.
Results
Amino acid analyses for 10 of the 22 organisms are presented in Table 1. The additional
12 organisms analyzed, but not shown in the
table, consisted of seven strains of Butyrivibrio
fibrlsolvens and five strains of Ruminococcus
flavefaciens. Except for valine, Strain 70; lysine, Strain GA 192; and glutamic acid, Strain
B 159, the distribution of amino acids in each
of the organisms was extremely uniform. Mean
values for all 22 organisms are presented in
Table 2. F o r comparative purposes the median
value of the results of Weller (10) and of
Hoeller and I-[armeyer (3) are also presented.
The only deviation of any note between the
amino acid values obtained by Weller (10) and
the mean values for the 22 organisms obtained
by us is that for lysine. A marked difference
between these results and the results of ttoeller
and Harmeyer (3) is apparent, however; Hoeller and Harmeyer's (3) results for valine, isoleucine, and leucine being markedly lower and
histidine values being much greater.
I n these amino acid analyses a peak invariably
appeared on the chromatogram in the position
of ornithine; if ornithine was indeed present it
presumably was so as a free amino acid. The
average distribution calculated as ornithine w a s
0.8 -----.8 g per ]00 g total amino acids.
The amino acid distributions of protozoal
preparations are presented in Table 2. These
distributions also show little variation. As with
the bacteria, the histidine values obtained by
tIoeller and Harmeyer (3) seem higher and the
lysine value for Entodinium is also quite high.
Biological values were calculated from each
of these amino acid distributions, using the
essential amino acid index method described by
Oser (7). An average value of 86% amino acid
nitrogen of total nitrogen was used to correct
for nonprotein nitrogen. This was the average
value obtained by us in this experiment. The
value obtained by Weller (10) was 75%. The
The principal source of amino acids leaving
the rumen and entering the alimentary tract of
the ruminant arise from bacterial, protozoal,
and undigested food proteins. The relative
proportions, together with the amino acid composition of each of these fractions, are the
principal factors influencing the distribution of
amino acids presented to the host animal.
Amino acid analyses of rumen bacterial and
protozoal preparations have been presented by
Weller (10) and Hoeller and Harmeyer (3).
The present work was undertaken to examine
the amino acid composition of hydrolysates of
individual strains of rumen bacteria, selected
for their differing substrate utilization characteristics.
Experimental
Procedure
Twenty-two strains of pure cultures of rumen
organisms were grown in 300 ml nonselective
media (1) in 500-ml round-bottomed flasks. The
organisms were harvested after 24 hr, homogenized, and subsamples taken for total nitrogen
and amino acid analysis. The samples for
amino acids were hydrolyzed in 6 N HCI for 18
hr at 121C, evaporated to dryness, and the
amino acids quantitated using a Technieon automatic analyzer. Norleucine was used as an internal standard and was added prior to byReceived for publication August 29, 1965.
81
D. B. PURSE1% AND S. l~I. BUECHLEI{
82
TABLE
1
A m i n o acid c o m p o s i t i o n of h y d r o l y s a t e s of i n d i v i d u a l r u m e n b a c t e r i a a n d c a l c u l a t e d
b i o l o g i c a l val ue s
Organism
Anlino acid
A
GA192
B
24
C
70
4.7
6.6
2.8
5.3
6.9
2.5
D
DI
E
B159
F
23
O
C94
H
7
I
B21a
J
H4a
6.4
4.7
2.9
5.7
7.9
5.0
9,7
2.3
5.2
6.9
3.3
7,2
8.1
5.2
9.9
2.0
(g/lO0 g total amino acids)
Threonine
Valine
Methionine
Isoleucinc
Leueine
Phenylalanine
Lysine,
tIistidine
7.0
6.5
5.7
11.4
2.2
6.3
5.2
8,3
2.2
4.9
6.5
2.7
7.4
8.2
5.6
9.1
2.0
4.1
6.2
2.7
5.5
6.4
4.4
8.3
1.9
4.9
6.4
2.9
6.4
8.6
5.3
9.1
2.4
5.0
6.5
2.2
5.6
6.5
4.7
7.3
2.2
4.4
6.3
1.3
7.5
7.1
5.2
10.9
2.5
7.7
5.3
14.9
2.1
8.2
5.6
8.5
2.2
Aspartic
Serine
Glutamic
Proline
Glycine
Alanine
Cystin e
Tyrosine
Diaminopimelic
Arginine
9.1
3.2
11.1
2.6
5.5
6.4
1.1
4.0
. .
5.3
12.1
3.8
11.1
4.4
6.0
6.3
.7
4.2
. .
419
9.9
3.5
10.3
3.9
5.9
5.3
,7
4.2
7
5.7
12.9
3.1
10.9
3.4
5.4
5.8
1.5
4.9
....
5.3
10.4
2.7
22.4
4.2
5.]
5.7
.7
3.2
7
5.0
11.6
3.3
11.3
4.0
5.8
5.8
1.6
5.3
.6
4,6
11.0
3.7
10.3
4.9
5.8
6.3
1.7
3.9
3.4
4.9
9.6
3.6
10.7
3.6
8.0
5.9
1.7
3.8
.6
5.6
]Biological w d u e
70
70
59
73
64
65
7.7
71
73
11.1
11.0
3.6
3.1
11.6
11.6
5.0
4.3
5.5
5.2
6.1
6.5
1.4
.7
4.5
4.9
........
6.3
4.9
69
71
" C a l c u l a t e d u s i n g e s s e n t i a l amino acid i n d e x (Ref. 7).
A (Selc~omonca~ r~tmina~tium), B (STtccinivibrio dextrinosolvc~ls), C (Bacteroides amylophib~s ) , D ( B u t y r i r i b r i o fibrisoh:ens ) , E ( Peptostreptococcus elsdenii ) , F ( Bacteroides ruminicola), G ( Ruminococc~s flavef aeie~Ts ) , H ( R,nminococcus albus ) , I ( Baeteroides s~wcinogenes ) ,
J ( B u t y r i v i b r i o fibrisolce~s)
TABLE 2
Amino acid c o m p o s i t i o n of h y d r o l y s a t e s of r u m e n b a c t e r i a a nd of p r e p a r a t i o n s of r m n e n
microbial proteins
Rumen protozoa
Rumen b a c t e r i a
a
b
c
d
b
Entodinium
c
Isotricha
c
(g/1OO g).
Threo nine
Va]ine
Methionine
Isoleueine
Leucinc
Phenylalanine
Lysine
Histidhle
5.5
6.6
2.6
6.4
7.3
5.1
9.3
2.3
--+ .8
~ 1.7
--+ .5
±
.7
+ 1.2
--+ .4
~ 1.7
--+ .3
5.4
6.7
2.9
6.2
7.6
4.9
7.8
2.0
4.9
4.2
3.0
3.6
4.7
4.9
9.7
6.3
5.1
5.2
2.2
6.9
8.1
6.2
10.1
2.1
4.7
5,4
2.1
7.0
8.3
6.1
9.8
1.8
5.8
4.6
1.4
5.8
8.1
6.1
13.1
3.2
5.2
4.0
2.0
5.7
7.3
3.8
9.2
4.3
Aspartic
Serine
Glu tami~
Prolino
G]ycine
Alanine
Cystin e
Tyro sin e
Diaminopimelie
Arginiue
11.1
3.8
11.9
4.1
6.1
6.5
1,0
4.2
.8
5.4
+-- 1.3
~ .9
± 2.4
-+" .6
± .7
± .7
--+ .7
--+ .6
~ .8
± .6
11.8
3.8
14.1
3.6
5.8
6.3
1.1
4.7
11.6
4.9
14.2
5.3
5.1
5.9
1.1
4.4
12.4
3.6
12.5
3.7
5.0
5.2
1.0
5,4
12.3
3.6
16.0
3.4
4.6
3.9
1.6
4.4
12.4
6.2
15.7
2.1
4.4
4.6
1.5
4.9
16.1
5.4
18.0
4.5
4.1
4.1
2.4
4.1
B i o l o g i c a l value
69
5.1
70
611
54
4.9
69
417
69
7.6
66
'~ Moan value and s t a n d a r d error of r e s u l t s f r o m a n a l y s e s of 22 orgunisms.
b M e d i a n value c a l c u l a t e d f r o m t h e r e s u l t s of W e l l e r (Ref. 10).
¢ C a l c u l a t e d f r o m the r e s u l t s of t I o e l l e r and H a r m e y e r (Ref. 3).
d A n a l y s i s of a p r o t o z o a l loreI>aration f r o m t h i s l a b o r a t o r y .
4.3
62
RUMEN ORGANISMS
biological values so calculated are presented in
Tables 1 and 2, but it should be emphasized that
these biological values are purely arbitra W and
are included for comparative purposes only.
As would be expected, the biological values were
quite uniform; however, that calculated from
results of Hoeller and Harmeyer (3) was only
54, whereas that for the present results and
the results of Weller (10) were 69 and 70,
respectively.
Discussion
These results support the conclusion that ramen bacterial protein varies little in amino acid
composition, even under widely differing dietary
regimes. The organisms used represented some
of the predominant organisms found in the
rumeu when either concentrates or roughages
are fed. Variations in the amino acid nitrogen
of the total nitrogen were encountered, however, ranging from 56 to 100%. While the
average value of 14% for nonamino acid nitrot e n was close to that found by Ellis and Pfander
(2) for rumen microbial polynucleotidM nitrogen, the fact that nonamino acid nitrogen included an undetermined quantity of anfide nitrogen makes such a comparison of little value.
Variations in per cent amino nitrogen with age
of culture are to be expected; this aspect was
not considered in the present work. The influence of different media upon amino acid distributions was not considered either.
I n the previous study by Weller (10) rumen
bacterial preparations were obtained from animals receiving four different rations; no differences in amino acid composition were apparent.
The present analysis of hydrolysates of individual rumcn bacteria confirms both the values
obtained by Weller (10) and the suggestion
that the amino acid composition of mixed bacterial proteins is almost constant, ttoeller and
IIarmeyer's (3) results do not confirm this
conclusion and the explanation for this discrepancy is not clear. Even though a markedly
different ration was used by ttoeller and l i a r meyer (3), a similar amino acid distribution
would be expected. The method of analysis
used by Hoeller and tIarmeyer (3) and Weller
(10) was essentially similar, both using the
procedure of Moore and Stein whereas that
used by us was an automated system. Thus,
the techniques used should not have resulted
in any discrepancies.
I t is of interest that biological values for the
bacterial and protozoal proteins from the present work and from that of Weller (10) (Table
2), calculated by the essential amino acid index
method of Oser (7), do not differ. Such a
83
result would agree with the findings of MeNaught et al. (6), who found biological values
of 80 and 81 for protozoal and bacterial protein, respectively, when fed as the protein source
to rats. Digestibility was different, giving rise
to different net protein utilization values for
these two protein sources. Perhaps tile most
signi~eant aspect, as yet not investigated, is
whether these two protein sources are supplementmT in nature. Thus, it is conceivable that
when supplied in combination the biological
value of the resultant mixture could be greater
than the biological value of either protein source
when fed alone.
Variations in the amino acid composition of
abomasal hydrolysates associated with dietary
regimes (8) suggest quantitative changes in the
relative proportions of protozoal, bacterial, and
undigested dietary protein fractions. I n this
regard 5icDonald (4) and McDonald and Hall
(5) demonstrated that 40 and 90% of zein and
casein, respectively, were converted to microbial
protein in the rulnen. While our results suggest
that little variation in the quality of the protein
presented to the animal in the form of bacterial
protein arises from variations in the composition of the bacterial population, differences in
digestibility and the pattern of absorption of
individual amino acids cannot, at the present
time, be disregarded as factors influencing the
quality of this protein fraction.
Acknowledgments
Acknowledgment is extended to Dr. Ken Pittman,
Bcltsville, and to Dr. Burk Dehority, Wooster, for
providing us with the bacteria. This work was
supported in part by Eli Lilly and Cmnpany.
References
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(2) Ellis, W. C., and Pfander, W. H. 1965.
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84
D. B. PURSER AND S. M. tlUECI-ILER
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