Cellobiose dehydrogenase formation by filamentous fungus Chaetomium sp. INBI 2-26(−)

Laccase-negative filamentous fungus INBI 2-26(−) isolated from non-sporulating laccase-forming fungal association INBI 2-26 by means of protoplast technique was identified as Chaetomium sp. based on partial sequence of its rRNA genes. In the presence of natural cellulose sources, the strain secreted neutral cellobiose dehydrogenase (CDH) activity both in pure culture and in co-culture with laccase-positive filamentous fungus INBI 2-26(+) isolated from the same association. INBI 2-26(−) also secreted CDH during submerged cultivation in minimal medium with glucose as the sole carbon source. Maximal CDH activity of 1 IU/ml at pH 6 with 2,6-dichlorophenolindophenol (DCPIP) as an acceptor was obtained on 12th day of submerged cultivation with filter paper as major cellulose source. Cellulase system of Chaetomium sp. INBI 2-26(−) capable of adsorption onto H3PO4-swollen filter paper consisted of four major proteins (Mr 200, 95, 65 and 55 K) based on SDS-polyacrylamide gel electrophoresis and was capable of DCPIP reduction without exogenous cellobiose.