Cellobiose dehydrogenase production by the genus cladosporium

ABSTRACT

Cellobiose dehydrogenase [CDH; EC.1.1.5.1] is an extracellular enzyme that mainly produced by wood-degrading fungi. It oxidizes cellobiose to cellobionolactone using a wide spectrum of electron acceptors. The key roles of CDH in growth, metabolism, and some other important cellular processes such as cellulose degradation in fungi have been noted. Since the demands for finding new sources of CDH among different organisms have been dramatically increased, this study was focused on the presence of CDH in the genus Cladosporium as a well-known cellulolytic fungus. Twenty strains of Cladosporium isolated from soil samples from different geographical origin were evaluated for CDH-producing ability. The early screening of the fungus by zymogram method revealed the presence of CDH as an extracellular form in all of the examined isolates. Submerged cultivation of the best producer of CDH [selected from initial screening] on a specific medium showed the maximum amounts of enzyme produced in shaking cultures with pH 4.5 at 28°C for a 14-day period. The enzyme activity was determined in the range of 27.83 to 1284.84 unit/mg protein among the isolates. Our observations show that Cladosporium isolates with high CDH producing ability i.e. isolates No. 10 and No. 18 can be used as selective candidates for large-scale production of this industrially important enzyme in further research programs. This is the first documented report on the presence of CDH in the fungus Cladosporium