Exocellular Carbohydrase Formation by Rumen Holotrich Ciliates

Abstract

SYNOPSIS Exocellular carbohydrase activity was detected, in the absence of cell lysis, in cell‐free culture supernatant fluids of rumen holotrich ciliates after incubations in buffer systems of varying tonicity, from cell suspensions that were isolated by various technics, and in which bacterial activity had been suppressed by antibiotics. The kinetic characteristics of the holotrich invertases and β–glucosidase from Dasytricha, although having interspecies variations, were the same for the intra‐ and extracellular form of the enzyme. The properties of the invertase activity present in cell‐free rumen contents resembled those of the exocellular enzymes formed by the holotrichs. Invertase activity in the in vitro culture supernatant fluid of Dasytricha ruminantium increased throughout the incubation period and was influenced by the initial pH, temperature, sucrose concentration, and inoculum size. Exocellular holotrich carbohydrase activity was increased when the incubation substrate was not readily utilized by the protozoa. Intracellular carbohydrase activity was also influenced by the carbohydrate substrate.

Polysaccharide-degrading enzymes formed by three species of anaerobic rumen fungi grown on a range of carbohydrate substrates

“…However, the cellulase of N. frontalis RK21 (Wood et al 1986), for example, is particularly active and extensively solubilises highly ordered crystalline cellulose. Likewise the specific activities of the fungal hemicellulases are comparable to or even higher than those reported in either mixed populations (Williams and Strachan 1984) or monocultures of rumen bacteria and protozoa (Williams and Coleman 1985;Williams andWithers 1981, 1985) and likewise warrant more detailed study.…”

“…As with bacterial cultures (e.g., Williams and Withers 1985) the enzyme titre in fungal cell-free supernatants also increases as the culture ages (Pearce and Bauchop 1985). The protozoal enzymes, however, are principally intracellular (Williams et al 1986), although some release of enzyme activity does occur (Akin and Amos 1979;Williams 1979). Polysaccharide-degrading enzymes were also present at the zoospore stage of the fungal life cycle.…”

“…with the rumen hemicellulolytic bacteria (Williams andWithers 1982a, 1982 b), the specific activities of the polysaccharidedegrading enzymes were influenced by the available growth substrate. Studies with N. frontalis (Orpin 1984;Orpin and Letcher 1979;Mountfort and Asher 1985) indicated that enzyme formation by this fungus was also substrate dependent and Mountfort and Asher (1 985) demonstrated that the production of carboxymethylcellulase was repressed by glucose and other soluble sugars (e.g., galactose, lactose) and that the soluble sugars were less effective inducers of cellulase.…”

The Rumen Microbial Ecosystem

“…Ryegrass hemicellulose and oat spelt xylan are degraded to alcohol-soluble oligomers, and the component monosaccharides by endoacting f3-D-xylanase( s), /3-D-xylosidase and a-L-arabinofuranosidase Williams and Coleman, 1985). Pectolytic and certain carbohydrase enzymes have been detected extracellularly (Abou Akkada and Howard, 1961;Williams, 1979b). Methanol is a product of pectin hydrolysis by both genera; polygalacturonic acid, oligo-uronides and galacturonic acid, unlike pectin, are not fermented by the holotrichs.…”

Molecular cloning, expression, and characterization of an endo-.BETA.-1,4-glucanase cDNA from Epidinium caudatum.

“…As a result, the growth and performance of nonruminant animals can be greatly improved by supplementing their diets with such enzymes. Besides rumen bacteria and fungi, rumen protozoa represent a potential and untapped source of enzymes, including cellulases, endoglucanases, xylanases, pectinases, chitinases, amylases, carbohydrases, invertases, and proteases (Abou Akkada and Howard, 1961;Bailey and Howard, 1963;Christie and Porteous, 1957;Coleman, 1983Coleman, , 1985Coleman, , 1986Coleman et al, 1980;Forsberg et al, 1984;Morgavi et al, 1994;Nagasawa et al, 1992Nagasawa et al, , 1994Williams, 1979;Williams and Coleman, 1985;Williams et al, 1984). These enzymes have great potential for a variety of agricultural and/or industrial processes.…”