BUTYRIVIBRIO SPP AND OTHER XYLANOLYTIC MICROORGANISMS FROM THE RUMEN HAVE CINNAMOYL ESTERASE-ACTIVITY

High concentrations of hydroxycinnamic acids in the hemicellulosic fra ction of dry season tropical grasses may influence the rate of microbi al degradation of arabinoxylans by ruminant animals. The ability of 22 strains of Butyrivibrio fibrisolvens, other ruminal bacteria (Ruminoc occus albus SY3, Ruminococcus flavefaciens RF1, Prevotella ruminicola AR20) and the ruminal phycomycete Neocallimastix patriciarum CX to dig est the tropical grass Heteropogon contortus (spear grass) and hydroly se esterified ferulic and p-coumaric acid was examined. Significant di gestion (8-36%) of spear grass occurred with the B. fibrisolvens strai ns H17c, A38, LP92-1-1, 49, R. albus SY3 and N. patriciarum. Hydrolysi s of ester-linked ferulic and p-coumaric acid occurred with all organi sms except B. fibrisolvens strains GS113, OB156 and LP1028 and P. rumi nicola AR20. The ratio of ferulic to p-coumaric acid hydrolysed by dif ferent strains of Butyrivibrio spp. varied markedly from 0.96 for AR 5 1 to 0.16 for A38. Butyrivibrios which were fibrolytic (H17c and A38) had higher extracellular cinnamoyl esterase activity than bacteria tha t did not digest spear grass fibre (LP 91-4-1 and AR 20) which had low activities or only produced cell associated enzyme. Cell associated a nd extracellular esterase activity were induced when Butyrivibrio spp. strains H17c, A38 and E14 and the Ruminococcus spp. were grown on bir chwood xylan but induction did not occur to the same extent with N. pa triciarum. This is the first reported observation of cinnamoyl esteras e activity in the genus Ruminococcus. The fungus N. patriciarum had si gnificantly higher digestibility of spear grass and solubilisation of phenolic acids than the bacteria. The study shows that high levels of extracellular cinnamoyl esterases are characteristic of a selection of fibre-degrading ruminal bacteria and fungi which probably indicates t hat these enzymes are common amongst xylanolytic ruminal microorganism s. (C) 1998 Academic Press.