*4.5. Enzyme Assay and Protein Measurement*

Enzyme activity was measured using dextran T70 as the substrate (3%, *m*/*v*) in 0.1 M Tris-HCl buffer (pH 8.0) using the 3,5-dinitrosalicylic acid method. Maltose served as the standard. One unit of dextranase activity was defined as the amount of enzyme capable of hydrolyzing dextran to 1 μM of reducing sugar in1 min [49]. Protein concentration was measured by the Bradford protein assay [50] using bovine serum albumin as the standard.

#### *4.6. Enzyme Properties*

#### 4.6.1. Effects of pH on Activity and Stability of Cadex

Dextranase activity was measured in buffers of different pH values and containing 3% dextran T70. To determine the effects of pH on dextranase stability, the enzyme solution was incubated at 25 ◦C for 1 h, and residual activity was measured at the optimum pH. Solutions (50 mM) with different pH values were used as follows: citrate buffer (pH 4.0–6.0), sodium phosphate buffer (pH 6.0–7.5), Tris-HCl (pH 7.5–9.0), and NaHCO3-Na2CO3 (pH 9.0–11.0).
