Some properties of the endo-(1 → 4)-β-<scp>D</scp>-glucanase synthesized by the anaerobic cellulolytic rumen bacterium <i>Ruminococcus albus</i>

Abstract

The extracellular and cell-bound cellulase (CM-cellulase) elaborated by the rumen bacterium Ruminococcus albus SY3 in synthetic medium was an endo-(1 → 4)-β-glucanase in that (i) it produced a rapid fall in the degree of polymerisation (1900 → 300) of H 3 PO 4 -swollen cellulose, while causing only 0.5% hydrolysis, and (ii) it released large amounts of cellotriose and smaller amounts of cellotetraose from H 3 PO 4 -swollen cellulose. The enzyme appeared in a wide range of molecular weights, which varied according to the culture conditions, but nevertheless focused at pH 6.0–6.1 in all cases in a pH gradient supported in a polyacrylamide gel. Cell-bound enzyme, which was of very large molecular weight (&gt; 1.5 × 10 6 ), was excluded from the polyacrylamide gel. Under certain conditions, cellulose swollen in H 3 PO 4 was hydrolysed extensively, but highly ordered cellulosic substrates were poorly hydrolysed. The enzyme acted synergistically with an endwise-acting cellobiohydrolase from the fungus Trichoderma koningii in solubilizing a microcystalline wood α-cellulose preparation (Avicel): the same cooperation was not apparent when Avicel was swollen in H 3 PO 4 or when cellulose in the form of cotton fibre was used.