CARBOHYDRASES OF THE RUMEN CILIATE EPIDINIUM ECAUDATUM (CRAWLEY). HYDROLYSIS OF PLANT HEMICELLULOSE FRACTIONS AND β-LINKED GLUCOSE POLYMERS

Abstract

Cell-free extracts from Epidinium ecaudatum (Crawley) hydrolysed the 3 hemicellulose fractions of pasture plants, but at different rates. All of the constituent monosaccharides are released from the hemicellulose fractions, galactose and uronic acids being liberated at much slower rates then pentoses. An arabinofuranosidase, which removes arabinose from highly branchedarabino-xylanbeforexylan chain can be hydrolysed, was isolated free from other pentosanases. A xylanase hydrolysing xylan (by random cleavage) and xylodextrins of degree of polymerization (D. P.) > 3 to xylotriose and xylobiose was isolated free from other pentosanases. A separate xylodextrinase hydrolysing (by random cleavage) xylodextrins of D. P. > 2 to xylobiose and xylose was also obtained; this enzyme did not hydrolyse xylan or xylobiose and the original extracts themselves possessed very weak xylobiase activity. The epidinial extracts hydrolysed laminaribiose, laminarin, lichenin and cellodextrins of D. P. < 7 rapidly, cellobiose and gentiobiose slowly but cellulose not at all. Polysaccharide glucose associated with plant linear B hemicellulose was liberated with cellobiose and possibly laminaribiose as intermediates. The cellodextrinase hydrolysed cellopentaose initially to cellobiose plus cellotriose and is a distinctly different enzyme from the xylanase and xylodextrinase. Extracts from Entodinium species and Eremoplastron bovis also hydrolysed all 3 types of plant hemicellose.