Carbohydrases of the rumen ciliate Epidinium ecaudatum (Crawley)

Abstract

Extracts prepared from the rumen protozoon, Epidinium ecaudatum (Crawley), under conditions which would not be expected to disrupt any associated bacteria, readily hydrolysed various plant hemicelluloses and starch. Xylobiose, cellobiose, sucrose, isomaltose and melibiose were also hydrolysed, but not cellulose. The hemicelluloses were hydrolysed to their constituent monosaccharides by a mechanism which involved the initial liberation of arabinose followed by the release of xylobiose and finally of xylose, glucose, galactose and uronic acid. The hydrolysis appeared to involve cleavage of xylobiose from the end of the xylan chain rather than random cleavage of the . chain. The hemicellulase and the xylobiase both possessed optimum activity in the pH range 5[center dot]8-6[center dot]2, and the hemicellulase activity was almost constant over the temperature range 37-51[degree].