Three thermostable neutral cellulases from Melanocarpus albomyces, a 20-kDa endoglucanase
(Cel45A), a 50-kDa endoglucanase (Cel7A), and a 50-kDa cellobiohydrolase (Cel7B) heterologously
produced in a recombinant Trichoderma reesei were purified and studied in hydrolysis
(50 °C, pH 6.0) of crystalline and amorphous cellulose. To improve their efficiency,
M. albomyces cellulases naturally harboring no cellulose-binding module (CBM) were
genetically modified to carry the CBM of T. reesei CBHI/Cel7A, and were studied under
similar experimental conditions. Hydrolysis performance and product profiles were
used to evaluate hydrolytic features of the investigated enzymes.
Each cellulase proved to be active against the tested substrates; the cellobiohydrolase
Cel7B had greater activity than the endoglucanases Cel45A and Cel7A against crystalline
cellulose, whereas in the case of amorphous substrate the order was reversed. Evidence
of synergism was observed when mixtures of the novel enzymes were applied in a constant
total protein dosage. Presence of the CBM improved the hydrolytic potential of each
enzyme in all experimental configurations; it had a greater effect on the endoglucanases
Cel45A and Cel7A than the cellobiohydrolase Cel7B, especially against crystalline
substrate. The novel cellobiohydrolase performed comparably to the major cellobiohydrolase
of T. reesei (CBHI/Cel7A) under the applied experimental conditions.
