Fractionation and identification of cellulases and other extracellular enzymes produced by sporotrichum thermophile during growth on cellulose or cellobiose
Canevascini, G.; Fracheboud, D.; Meier, H.
Canadian Journal of Microbiology 29(9): 1071-1080
ISSN/ISBN: 0008-4166 Accession: 005483479
The extracellular enzyme proteins secreted by S. thermophile, ATCC 42464, upon growth on cellulose or cellobiose, were separated by polyacrylamide gel electrophoresis and electrofocusing into different fractions which were then analyzed with respect to their enzymatic character to identify the cellulolytic enzymes. A positive reaction against carboxymethylcellulose azure (CMC azure) was taken as evidence for an endo-acting cellulase, whereas the criterion for the presence of an exo-cellulase was a negative reaction with CMC azure and a concomitant increase in reducing power upon action of any kind of cellulose. With this procedure, 4 main cellulolytic enzymes were detected: 3 endo-cellulases, named endo-cellulases I, II, and III (with corresponding isoelectric points 5.1, 4.2, 5.7) and an exo-cellulase (isoelectric point 4.7). With respect to their enzymatic action on amorphous cellulose, endo-cellulases I and III were isofunctional, releasing cellobiose and cellodextrins as hydrolytic products, whereas endo-cellulase II additionally produced some glucose. Endo-cellulases I and III were also able to attack native (crystalline) cellulose like filter paper or Avicel, but endo-cellulase II could not and thus behaved as a true carboxymethylcellulase. The rate of formation of endo-cellulase I during growth was distinctly superior from that of the other cellulases so that the proportion of the activity due to endo-cellulase I compared with that due to the others constantly increased during the culture.