Partial characterization of the extracellular carboxymethylcellulase activity produced by the rumen bacterium Bacteroides succinogenes

Abstract

In cultures of Bacteroides succinogenes, in which cellulose was the source of carbohydrate, from 70 to 80% of the carboxymethylcellulase (CMCase) activity was present in the culture fluid. The crude extracellular enzyme readily hydrolyzed acid-swollen cellulose with the production of glucose and cellobiose. Of this extracellular CMCase, 50-62% was associated with sedimentable membrane fragments, 9-13% with nonsedimentable material with a molecular weight greater than 4 X 10(6), and 28-38% with molecules having a molecular weight of approximately 45 000. Polyacrylamide gel electrophoresis (PAGE), in the presence of sodium dodecyl sulfate, revealed that both the nonsedimentable and the sedimentable fraction had complex protein compositions. The nonsedimentable and sedimentable CMCase fractions, after treatment with Triton X-100, were subjected to PAGE in the presence of 0.2% (w/v) Triton X-100. The results indicated the presence of fast- and slow-migrating CMCases in the former, and of a slow-migrating CMCase in the latter. An apparently uncharged CMCase, which probably corresponded to the slow-migrating component by PAGE, was partially purified from the concentrated culture supernate by solubilization in Triton X-100 and chromatography on DEAE--Sepharose, CM--Sepharose, and Phenyl--Sepharose. The partially purified CMCase had a pH optimum of 5.6-6.6 and a temperature optimum of 50 degrees C.