LOCALIZATION OF CELLOBIOSE DEHYDROGENASE IN CELLULOSE-GROWN CULTURES OF PHANEROCHAETE-CHRYSOSPORIUM

To elucidate the function of cellobiase dehydrogenase (CDH) in cellulo se degradation by Phanerochaete chrysosporium, production and localiza tion of CDH were investigated and compared with those in shaking and a erated static cultures grown on cellulose. Substantial CDH activity wa s detected in the medium of the shake cultures after 8 days of incubat ion, while no CDH activity was detected in the medium of static cultur es at any point during the incubation period. Light microscopy clearly showed that many cellulose particles were adsorbed on the surface of the hypha in static cultures, whereas no cellulose particles were adso rbed to the hypha in shake cultures. The addition of laminarinase to s tatic cultures was very effective in detaching cellulase particles fro m the hypha surfaces. Using a potentiometric assay performed with an o xidation-reduction potential electrode, some CDH activity could be det ected on the hypha/cellulose complexes in static cultures. Thus, CDH i s produced also in static cultures, albeit in lower amounts than in sh ake cultures, but tt-le enzyme is not released into the medium. It see ms likely that the beta-1,3-glucan layer plays an important role in CD H localization and cellulose degradation. Immunocytochemical confocal laser scanning microscopy for the static cultures demonstrated that mo st GDH was adsorbed on the surface of the cellulose, especially around the cracks, which were formed by the action of cellulases during the course of incubation. From these observations, we conclude a direct pa rticipation of CDH in the degradation of cellulose in cooperation with cellulases. (C) 1997 Academic Press.