Characteristics of galactomannanase for degrading konjac gel

Abstract

Galactomannanase (Glmnase) is an enzyme product derived from Aspergillus niger. The activity of Glmnase degrading (hydrolyzing) the konjac gel were investigated. Significant loss in the enzyme activity was found when the temperature above 60 °C. Similar observations were obtained when the reaction pH above 5. Further increase in the pH value resulted in entirely loss of enzyme activity at the alkaline pH region (pH 8.0 and above). The optimal hydrolyzing temperature and pH were at 60 °C and 5.0, respectively. For the stability test, the purified Glmnase increased its thermostability up to 70 °C at pH 5.0, but it retained only about 60% activity after 60 min incubation at this temperature and its activity became zero after 20 min incubation at 80 °C. The Glmnase was stable at the pH range from 3.0 to 7.0 at room temperature and retained at least 80% activity for 60 min. For the storage temperature test, the lyophilized Glmnase still conserved about 90% activity during 7 days at 30 °C, and was higher than about 80% at 4 °C. The K m and V max, were 0.018 mg/ml konjac powder and 0.20 mg/ml reducing sugar per min, respectively.