2.2. Dextranase activity
This was initially determined by three different methods. A spectrophotometric method [13] measured reducing sugar from dextranase action on dextran (T2000
TM
, Pharmacia MW 2,000,000 Da), which reacts with 3,5 dinitrosalicyclic acid to give a yellow–brown colour, which is measured at 540 nm. One dextranase unit (DU) is the amount of enzyme that degrades dextran to produce reducing sugar equivalent to 1 mg maltose per hour at 40 8C and pH 5.4. A titration method [14] was modified (see [15] for full method) to measure reducing sugar from dextranase action on dextran T2000
TM
, and the reducing sugar is determined by the Hanes method [14]. One dextranase unit (DU/ml) is the amount of enzyme that degrades dextran T2000
TM
to produce reducing sugar corresponding to the reducing power of 1 mmol of
sodium thiosulphate in 1 min at 37 8 C and pH 5.8. Relative dextranase activities of the different enzymes studied were confirmed by comparison of ion chromatograms, after dextran (T2000
TM
; 500 ppm) was digested by the dextranase (0.015 g/100 ml acetate pH 5.4 buffer [13.5 g sodium acetate trihydrate was dissolved in 900 ml of 18 V deionized water, and the pH adjusted to pH 5.4 with 1 N acetic acid]) for 30 min at 40 8 C in a shaking (90 rpm) water-bath (Julaba SW22).
2.2. Dextranase activity
This was initially determined by three different methods. A spectrophotometric method [13] measured reducing sugar from dextranase action on dextran (T2000
TM
, Pharmacia MW 2,000,000 Da), which reacts with 3,5 dinitrosalicyclic acid to give a yellow–brown colour, which is measured at 540 nm. One dextranase unit (DU) is the amount of enzyme that degrades dextran to produce reducing sugar equivalent to 1 mg maltose per hour at 40 8C and pH 5.4. A titration method [14] was modified (see [15] for full method) to measure reducing sugar from dextranase action on dextran T2000
TM
, and the reducing sugar is determined by the Hanes method [14]. One dextranase unit (DU/ml) is the amount of enzyme that degrades dextran T2000
TM
to produce reducing sugar corresponding to the reducing power of 1 mmol of
sodium thiosulphate in 1 min at 37 8 C and pH 5.8. Relative dextranase activities of the different enzymes studied were confirmed by comparison of ion chromatograms, after dextran (T2000
TM
; 500 ppm) was digested by the dextranase (0.015 g/100 ml acetate pH 5.4 buffer [13.5 g sodium acetate trihydrate was dissolved in 900 ml of 18 V deionized water, and the pH adjusted to pH 5.4 with 1 N acetic acid]) for 30 min at 40 8 C in a shaking (90 rpm) water-bath (Julaba SW22).
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