Expression of a modified Neocallimastix patriciarum xylanase in Butyrivibrio fibrisolvens digests more fibre but cannot effectively compete with highly fibrolytic bacteria in the rumen.
OBJECTIVE
This study investigated the competitive abilities of two Neocallimastix patriciarum-derived xylanases constructs in Butyrivibrio fibrisolvens H17c (xynA and pUMSX) and their ability to compete in vivo.


RESULTS
The digestibility of neutral detergent fibre (NDF) increased during co-culture of xynA or pUMSX and weakly cellulolytic, but not with highly cellulolytic, ruminococci. Competition studies among xynA, pUMSX and cellulolytic consortia demonstrated that xynA was the fittest. XynA did not persist at high levels in the rumen and was undetectable after 22 days.


CONCLUSIONS
The construction of recombinant xylanolytic B. fibrisolvens does improve the digestibility of fibre above that of the native, but digestibility is still less than that of the most potent fibre digesters such as ruminococci.


CONCLUSIONS
Fibre digestion may be improved by genetic manipulation of ruminal bacteria but ecological parameters, such as persistence in vivo and the niche of the organism, must be taken into account.
Krause
D O
DO
CSIRO Livestock Industries, Long Pocket Laboratories, Indooroopilly, Queensland, Australia. denis.krause@tag.csiro.au
Bunch
R J
RJ
Dalrymple
B D
BD
Gobius
K S
KS
Smith
W J
WJ
Xue
G P
GP
McSweeney
C S
CS
D000818:Animals; D001421:Bacteria, Anaerobic / Q000201:enzymology* / Q000235:genetics; D002417:Cattle; D004043:Dietary Fiber / Q000378:metabolism*; D020088:Neocallimastix / Q000201:enzymology* / Q000235:genetics; D006109:Poaceae / Q000382:microbiology; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000378:metabolism; D012417:Rumen / Q000382:microbiology*; D012756:Sheep; D043325:Xylan Endo-1,3-beta-Xylosidase; D014995:Xylosidases / Q000235:genetics / Q000378:metabolism*
D004043:Dietary Fiber; D011994:Recombinant Proteins; D014995:Xylosidases; D043325:Xylan Endo-1,3-beta-Xylosidase