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 fluid of sheep and either grown in vitro or inoculated into the rumen of the ciliate-free sheep. Population density of ciliates in vitro was about 320 cells/ml when culture salt solution was supplemented with hay (0.6 mg/ml/d) and 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 440 cells/ml (P < 0.01). Conversely, oat spelt xylan decreased the concentration of protozoa to 250 cells/ml (P < 0.05). Ciliates readily ingested and digested cellulose particles while xylan particles were only sporadically engulfed. 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. Carboxymethylcellulose and xylan were degraded at 17.5 and 66.6 muM reducing sugars released from substrate/mg protein/ml. Degradation rate of microcrystalline 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 the presence of three protein bands active against CMC and two protein bands degrading xylan. Thin layer chromatography showed a presence of only oligosaccharides in the end products released from CMC and xylan by enzymes isolated from gel slices. Neither glucose nor xylose were found there. Conversely only glucose was detected by TLC following incubation of microcrystalline cellulose with solution of protozoal protein. The same preparation released mainly xylose from xylan but different oligosaccharides were also present.