Fig. 7.

Biochemical characterization of glycosidase preparations. The protein fractions isolated by affinity digestion of the cell-free culture supernatants of C. bescii (solid symbols, solid lines) and C. obsidiansis (open symbols, dashed lines) were examined for optimal reaction parameters and thermostability in triplicate CMCase assays at 80°C (B to D) or at various temperatures of 40 to 100°C (A). To determine the pH optimum, values were measured at pHs of 3.5 to 6.5 in 50 mM citrate buffer (circles) and at pHs of 6.5 to 8 in 50 mM potassium phosphate buffer (squares). The thermostability of the C. bescii (C) and C. obsidiansis (D) enzyme mixtures was measured by incubating the protein samples for 30, 60, or 90 min at 75, 85, or 95°C before starting the CMCase assay by substrate addition. Both preparations showed slightly increased activity upon preincubation for 30 and 60 min. The C. bescii enzyme mixture retained 10 to 20% of its activity upon preincubation for 90 min at 95°C, while the C. obsidiansis mixture retained up to 40%.