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A Study of the Optimal Conditions for Starch Hydrolysis Through Thermostable Α - Amylase

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T. Kolusheva, A. Marinova Journal of the University of Chemical Technology and Metallurgy, 42, 1, 2007, 93-96 A STUDY OF THE OPTIMAL CONDITIONS FOR STARCH HYDROLYSIS THROUGH THERMOSTABLE α - AMYLASE T. Kolusheva, A. Marinova University of Chemical Technology and Metallurgy 8 Kl. Ohridski, 1756 Sofia, Bulgaria E-mail: e-mail: manahova@abv.bg. Received 10 July 2006 Accepted 12 November 2006 ABSTRACT The present work determines the optimal conditions for starch hydrolysis by thermostable α -amylase (EC 3.2.1.1) produced by Bac.subtilis strain XÊ-86. The hydrolysis reaction has the greatest rate at pH = 7.0, starch substrate concentration 250 g.l-1, enzyme concentration – 12 enzyme units per ml suspension and 90o C temperature. We …show more content…

The amount of the reducing sugars like glucose or inverted sugar contained in the sample is calculated from the quantity of the Cu2+ from the Fehling solution which have undergone a reaction with the sugar, by using the Bertrand tables [4]. RESULTS AND DISCUSSION To study the optimal conditions for the hydrolysis of starch with the a – amylase enzyme XK – 60 under consideration, we have varied the following factors: concentration of the substrate, concentration of the enzyme, temperature of the hydrolysis, pH and the influence of inhibitors. In order to determine the optimal concentration of the substrate we have done experiments in the range from 100 to 300 g.l-1 starch. From the results presented in Table 1 it is evident that for substrate concentrations 250 and 300 g.l-1, the level of hydrolysis is almost the same (30.1 % and 30.3 % respectively). We supposed that this was most likely due to the inhibiting action of the reducing sugars obtained during hydrolysis at substrate concentrations higher than 250 g.l-1. To prove this hypothesis, we investigated the influence of the concentration of the glucose added to the substrate on the rate of the enzymatic reaction. As can be seen from Fig. 1, the addition of glucose in the beginning of the hydrolysis process significantly reduces the reaction rate of the process. The

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