Ability of the rumen ciliate Epidinium ecaudatum to digest and use crystalline cellulose and xylan for in vitro growth

The rumen ciliate protozoan Epidinium ecaudatum was isolated from rumen flu id of sheep and either grown in vitro or inoculated into the rumen of the c iliate-free sheep. Population density of ciliates in vitro was about 320 ce lls/ml when culture salt solution was supplemented with hay (0.6 mg/ml/d) a nd wheat gluten (0.15 mg/mg/d). Addition of the microcrystalline cellulose (0.25 mg/ml/d) to the control diet increased the ciliate numbers to about 4 40 cells/ml (P < 0.01). Conversely, oat spelt xylan decreased the concentra tion of protozoa to 250 cells/ml (P < 0.05). Ciliates readily ingested and digested cellulose particles while xylan particles were only sporadically e ngulfed. Only glucose was released from the microcrystalline cellulose and cellobiose during incubation of the both substrates with protozoal protein; the release rate was 0.19 and 14.9 muM/mg protein/h, respectively. Carboxy methylcellulose and xylan were degraded at 17.5 and 66.6 muM reducing sugar s released from substrate/mg protein/ml. Degradation rate of microcrystalli ne cellulose, carboxymethylcellulose, cellobiose and xylan was the highest at pH 6.5, 5.5, 6.0 and 6.5, respectively. Non-denaturating polyacrylamide gel electrophoresis combined with CMC-ase and xylanase zymogram revealed th e presence of three protein bands active against CMC and two protein bands degrading xylan. Thin layer chromatography showed a presence of only oligos accharides in the end products released from CMC and xylan by enzymes isola ted from gel slices. Neither glucose nor xylose were found there. Conversel y only glucose was detected by TLC following incubation of microcrystalline cellulose with solution of protozoal protein. The same preparation release d mainly xylose from xylan but different oligosaccharides were also present .