Factors Affecting Cellulolysis by Ruminococcus albus

Abstract

The factors influencing the digestion of pebble-milled cellulose by enzymes were studied by using several strains of Ruminococcus albus including a mutant characterized by a more eccentric location of its colony in the clearing produced by digestion of the cellulose in the thin layer lining the wall of a culture tube. Most of the cellulase is extracellular. As much as 65% of the cellulose could be digested by the cell-free enzymes provided the quantity of cellulose was small. Fresh enzyme was repeatedly administered or the digestion experiment was arranged in a dialysis bag through which digestion products could diffuse. Cellobiose and, to a lesser extent, glucose inhibited digestion. Pebble-milled filter paper, moist crystalline cellulose from cotton, and dry crystalline cellulose (Sigmacel) were digested, but in decreasing rapidity, respectively. Carboxymethylcellulose was digested more rapidly than pebble-milled cellulose but to approximately the same final extent as judged by Cu reduction values. Cell walls from alfalfa were digested. The enzyme preparation was active over the pH range 6.0 to 6.8 and showed most rapid cellulose digestion at 45 C. Part of the cellulolytic activity was irreversibly destroyed by exposure to oxygen. Much of the enzyme was absorbed on cellulose. The absorption and desorption characteristics, as well as the partial inhibition by oxygen, indicate that multiple enzymes are involved. 729

Factors Affecting the Activity of Cellulases Isolated from the Rumen Digesta of Sheep

“…The anaerobic environment of rumen contents together with the low redox potential (8) protective agent DTT in all solutions used in the current work. Published results of experiments with cellulases ioslated from the rumen or of pure cultures of rumen microorganisms differ in their sensitivity to oxygen and the protection obtained with cysteine or other reducing agents (10,12,20). In our experiments addition of DTT at a concentration of 1 mM in the assay had no effect on cellulase activity, and neither did the exclusion of oxygen by flushing with high-purity nitrogen.…”

Unique and shared responses of the gut microbiota to prolonged fasting: a comparative study across five classes of vertebrate hosts

“…The normal function of Coprobacillus in the gut is unclear, although it has been implicated in several gastrointestinal diseases (Keren & Gophna, ; Pontarelli et al ., ). Ruminococcus is known for its fiber‐degrading capabilities (Smith et al ., ), and thus, lack of dietary substrates during host fasting may cause its decline in relative abundance. All hosts with ceca (tilapia, quail, mice) exhibited increases in the abundance of Oscillospira and decreases in Prevotella and Lactobacillus within this chamber.…”

Production and regulation of cellulase by two strains of the rumen anaerobic fungus Neocallimastix frontalis

“…Until recently, cellulosic materials in the rumen were thought to be attacked by only bacterial and perhaps protozoal cellulases. The cellulases of the major rumen cellulolytic bacteria, Ruminococcus albus, Ruminococcus flavefaciens, and Bacteroides succinogenes, have been widely studied (9, 10, 15, 29,33,37). Consequently, the nature and regulation of rumen bacterial cellulases, particularly those of R. albus, are now better understood (10,33).…”