Summary

Mixed populations of human gut bacteria degraded cas casein by producing a variety of cell-bound and extracellular proteolytic enzymes. Casein was initially hydrolysed to TCA soluble peptides which were subsequently broken down to volatile fatty acids, ammonia, dicarboxylic acids and a range of phenolic compounds. Amino acids did not accumulate to any extent during casein breakdown, suggesting that the rate of peptide hydrolysis was the limiting step in protein utilisation by these bacteria. Similar fermentation products were produced from bovine serum albumin, however, the insoluble protein collagen was considerably more resistant to degradation by the colonic microflora, as evidenced by the reduced quantities of fermentation end-products formed.

References

[1]
Moore
W.E.C.
Holdeman
L.V.
(
1974
)
Human fecal flora: the normal flora of 29 Japanese-Hawaiians
Appl. Environ. Microbiol.
 ,
27
,
961
979
.
[2]
Cummings
J.H.
(
1981
)
Cellulose and the human gut
Gut
 ,
25
,
805
810
.
[3]
Cummings
J.H.
(
1981
)
Dietary fibre
Br. Med. Bull.
 ,
37
,
65
70
.
[4]
Roediger
W.E.W.
(
1980
)
Role of anaerobic bacteria in the metabolic welfare of the colonic mucosa in man
Gut
 ,
21
,
793
798
.
[5]
Wrong
O.M.
Edmonds
C.J.
Chadwick
V.S.
(
1981
)
The Large Intestine: Its Role in Mammalian Nutrition and Homeostasis
 
MTP Press
Lancaster.
[6]
Cruickshank
R.
(
1965
)
Medical Microbiology
 , pp
886
889
Livingstone
, Edinburgh.
[7]
Lowry
O.H.
Rosebrough
N.J.
Farr
A.L.
Randall
R.J.
(
1951
)
Protein measurement with the folin phenol reagent
J. Biol. Chem.
 ,
143
,
265
275
.
[8]
Solorzano
L.
(
1969
)
Determination of ammonia in natural waters by the phenolhypochlorite method
Limnol. Oceanogr.
 ,
14
,
799
801
.
[9]
Holdeman
L.V.
Cato
E.P.
(
1977
)
Moore
W.E.C.
, Ed)
4th ed.
, In
Anaerobic Laboratory Manual
 
VPI Anaerobic Laboratory
, Blacksburg, VA.
[10]
Adams
R.F.
Jones
R.L.
Conway
P.L.
(
1984
)
High-performance liquid chromatography of microbial acid metabolites
J. Chromatogr.
 ,
336
,
125
137
.
[11]
Mahadevan
S.
Erfle
J.D.
Sauer
F.D.
(
1979
)
A colorimetric method for the determination of proteolytic degradation of feed proteins by rumen micro-organisms
J. Animal Sci.
 ,
48
,
947
953
.
[12]
Hazlewood
G.P.
Edwards
R.
(
1981
)
Proteolytic activities of a rumen bacterium Bacteroides ruminicola R8/4
J. Gen. Microbiol.
 ,
125
,
11
15
.
[13]
Brock
F.M.
Forsberg
C.W.
Buchanan-Smith
J.G.
(
1982
)
Proteolytic activity of rumen micro organisms and effects of proteinase inhibitors
Appl. Environ. Microbiol.
 ,
44
,
561
569
.
[14]
Finegold
S.M.
Sutter
V.L.
Mathisen
G.E.
(
1983
) In
Human Intestinal Microflora in Health and Disease
 
Hentges
D.J.
, Ed) pp
3
31
Academic Press
, London.
[15]
Hill
G.B.
(
1981
) In
The Prokaryotes
 
Starr
M.P.
, Ed) pp
1631
1649
Springer-Verlag
, Berlin.
[16]
Macfarlane
G.T.
Allison
C.
Cummings
J.H.
(
1985
)
Contribution of the microflora to proteolysis in the colon
2nd ed.
,
63
, In
Proc. XIII Int. Cong. Nutr.
 .
[17]
Prynne
C.J.
Southgate
D.A.T.
(
1979
)
The effects of a supplement of dietary fibre on faecal excretion by human subjects
Br. J. Nutr.
 ,
41
,
495
503
.
[18]
Cummings
J.H.
(
1981
)
Short-chain fatty acids in the human colon
Gut
 ,
22
,
763
779
.
[19]
Drasar
B.S.
Hill
M.J.
(
1974
)
Human Intestinal Flora
 
Academic Press
London.
[20]
Cummings
J.H.
Hill
M.J.
Bone
E.S.
Branch
W.J.
Jenkins
D.J.A.
(
1979
)
The effect of meat protein and dietary fibre on colonic function and metabolism, Part II. Bacterial metabolites in faeces and urine
Am. J. Clin. Nutr.
 ,
32
,
2094
2101
.
[21]
Miller
T.L.
Weaver
G.A.
Wolin
M.J.
(
1984
)
Methanogens and anaerobes in a colon segment isolated from the normal fecal stream
Appl. Environ. Microbiol.
 ,
48
,
449
450
.