To be able to study cellulose (Solka-floc) degradation without micro­bial conversion of the sugars formed, separate hydrolysis experiments were carried out in stirred flasks without cells. The conditions in these experiments were the same as during the corresponding fermentation (i. e., the same medium composition, pH 5.0, 28°C, 600 rpm). The medium composition was set according to the assumption that at the moment of Solka-floc addition, the fermentation broth would be depleted for the glucose originally present. The medium for hydrolysis experiments thus contained a single set of nutrients, 10 g/L of Solka-floc as the substrate, and added enzyme giving a desired activity. Two sources of enzyme were used: either Celluclast, a commercially available fungal cellulase prepara­tion (a kind gift from Novozymes, Denmark) or a home-produced cellu — lase enzyme prepared by collecting the supernatants of Solka-floc grown in shake-flask cultures of T. reesei Rut-C30 (Mandels medium, 28°C, pH 5.0, 4 d) by centrifugation (5600g, 10 min). The enzyme-to-substrate ratio was adjusted to mimic two chosen specific points in the batch cultivation on cellulose: the point of cellulose addition and the point at which the CO2 evolution peaked. Experiments were run in duplicate.

Results

T. reesei Rut C-30 was grown aerobically in batch cultures in two stages, using glucose in an initial phase to produce cell mass, and thereafter adding cellulose (in the form of Solka-floc) as described before. The dynamics of cellular activity and produced cellulases following the addition of Solka — floc was monitored by on-line measurements of CO2 evolution and sam­pling for determination of enzyme activity and sugar concentrations.