Fig. 4.

Fig. 4. Biochemical characteristics of the purified xylanase from S. viridodiastaticus MS9. The following enzymatic reaction was performed at 60°C for 10 min in 20 mM Tris-Cl (pH 7.0) buffer using beechwood xylan as a substrate unless otherwise specified. (A) Effect of pH. The xylanase assay was performed under different pH conditions. Values obtained with 20 mM Tris-Cl (pH 7.0) were considered 100%. ●, 20 mM MOPS buffer; ■, 20 mM Tris-Cl buffer. (B) Effects of temperature. The xylanase assay was carried out at different temperatures ranging from 40°C to 70°C. The values obtained at 60°C were taken to be 100%. (C) Temperature stability. The enzyme was heat-treated at the indicated temperatures for 10, 20, 30, 60, and 120 min, and residual enzyme activity was measured. The activity value without preincubation was set to 100%. ●, 60°C; ■, 65°C; ♦, 70°C. (D) The effects of metal ions and chelating reagents. Each compound was added to the reaction mixture at a final concentration of 5 mM. The enzyme activity in the absence of chemicals was 100%. (E) Determination of kinetic parameters. Lineweaver-Burke plots were used to determine the kinetic parameters of the purified xylanase acting on beechwood xylan. Data are shown as mean values of at least three replicate experiments.

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