Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/9/2003
Publication Date: 10/1/2003
Citation: REVENEAU, C., ADAMS, S.E., COTTA, M.A., MORRISON, M. PHENYLACETIC AND PHENYLPROPIONIC ACIDS DO NOT AFFECT XYLAN DEGRADATION BY RUMINOCOCCUS ALBUS. APPLIED AND ENVIRONMENTAL MICROBIOLOGY. 2003. V. 69. P. 6954-6958. Interpretive Summary: Digestion of plant cell wall carbohydrates, including hemicellulose (xylan), is an essential function in the nutrition of ruminant livestock species like cattle (dairy and beef) and sheep. This digestion is carried out by a specialized group of microorganisms that inhabit the rumen or forestomach of these animals. Improving our understanding of how these organisms perform this function could lead to development of feeding and management strategies to improve the efficiency of digestion and, therefore, animal productivity. Previously, it was shown that one of the major bacteria that digests cell wall carbohydrates, Ruminococcus albus, would digest the cellulose in cell walls more effectively if provided with the chemicals phenylacetic (PAA) and phenylpropionic acids (PPA). In the current study, we examined whether the provision of these chemicals would affect the digestion of hemicellulose (xylan). Although adding PPA/PAA to cultures of this organism resulted in some changes in the types and location of digestive enzymes produced, it did not alter the ability of the bacterium to digest and utilize xylan. This information will be useful to other researchers studying digestion in ruminant livestock.
Technical Abstract: Since the addition of either ruminal fluid or a combination of phenylacetic and phenylpropionic acids (PAA/PPA) has previously been shown to dramatically improve cellulose degradation and growth of Ruminococcus albus, it was of interest to determine the effects of these additives on xylan-grown cultures. Although cell-bound xylanase activity increased when either PAA/PPA or ruminal fluid was added to the growth medium, total xylanase did not change, and neither of these supplements affected the growth or xylan-degrading capacity of R. albus 8. Similarly, neither PAA/PPA nor ruminal fluid affected xylan degradation by multiple strains of R. albus when xylan prepared from oat spelts was used as a carbohydrate source. These results show that the xylanolytic potential of R. albus is not conditional on the availability of PAA/PPA or other components of ruminal fluid.