Abstract: A novel method for the quantitative determination of trace amounts of xylanase activity was established. The chromogenic conditions were explored according to the properties of xylan and its hydrolysates. The effects of several key hydrolysis parameters on the determination of xylanase activity were investigated by multiple-point procedures. The results showed that protein concentrations less than 30μg/mL did not interfere with the determination of xylanase activity. The optimal xylan concentration for the determination of xylanase activity was 4 mg/mL. High hydrolysis temperatures could inactivate xylanase. The most appropriate temperature for determining xylanase activity was 30 ℃, much lower than the optimal reaction temperature. The hydrolysis time was controlled within 60 min. The reaction time between hydrolysates and MBTH reagent was 13－16 min with the optimal level of 15 min. Based on 30 min hydrolysis, the detection limit and quantitation limit of the method were 0.135 mu/mL and 0.451 mu/mL, respectively. Properly prolonged hydrolysis time could improve the sensitivity of the method. The method was accurate, stable and even more sensitive than the DNS method.

Key words: xylanase, MBTH, activity, xylan, xylose, determination