Preparation of the cellulase from the cellulolytic anaerobic rumen bacterium Ruminococcus albus and its release from the bacterial cell wall

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Abstract
Most of the cellulase (CM-cellulase) elaborated by the rumen bacterium R. albus strain SY3, which was isolated from a sheep, was cell wall bound. The enzyme could be released readily by washing with phosphate buffer or with water. The amount of enzyme released was affected by the pH and ionic strength of the phosphate buffer. The cell wall bound enzyme was of very high MW (> 1.5 .times. 106) as judged by its chromatographic behavior on Sephacryl S-300. The MW of the extracellular enzyme was variable and depended on the culture conditions. When cellobiose was used as the energy source and the medium contained rumen fluid (30%), the extracellular enzyme was mainly of high MW. When cellulose replaced the cellobiose, the cell-free culture filtrate contained only low MW enzyme (MW .apprx. 30,000) in late stationary phase cultures (7 days). Cultures that did not contain rumen fluid contained mainly low MW enzyme. Under some conditions the high MW enzyme could be broken down to some extent into low MW enzyme by treatment with dissociating agents. Cell-free and cell wall bound enzymes showed the same relationship when the change in fluidity effected by them on a solution of CM-cellulose was plotted against the corresponding increase in reducing sugars, suggesting that the enzyme were the same. R. albus cellulase may exist as an aggregate of low MW cellulase components on the bacterial cell wall and in solution under certain conditions.