KINETICS OF HYDROLYSIS OF STARCH BY ALPHA- AMYLASE FROM FREE AND IMMOBILISED Bacillus subtilis ON Raphia sudanica CHIPS

Abstract

The desire in this work is to determine optimal conditions suitable [or the microbe (Bacillus subtilis) and enzymes (a amylase) to produce high level of sugar. In this study a amylase from free and immobilized Bacillus subtilis on chips of Raphia sudanica was used to catalyse the hydrolysis of starch using batch and feed batch processes respectively. Raphia sudanica was cut to size and severally boiled for purification and then used for immobilization of Bacillus subtilis. The total sugar produced was monitored using the Somogyi-Nelson method. Optimal operating conditions such as temperature and pH were investigated and Michaelis Menten equation was employed to determine the kinetic param~ters for both the free and immobilized processes. The optimum temperature, pH as well as the activation energy were 50oC, 5.0, 6.5kJ / mol and 70oC, 5.0, 22.6kJ / mol for the free and immobilized processes, respectively. The Michaelis Menten constant and maximum rate of hydrolysis was 0.03352 mol and 40.0/1 mol/min, respectively, for the free process. Similarly, for the immobilized process, the apparent Michaelis Menten constant and apparent maximum rate of . hydrolysis were 0.05044 mol and 125.0/1 mol/min respectively. The substrate flow rate employed during the immobilized process was 12ml/min. Regardless of whether the process was free or immobilized, the slight acidic pH medium of 5.0 was most suitable for the bacteria and its enzyme. The a - amylase from immobilized Bacillus Subtilis showed its resilience at high temperature by exhibiting optimal activity. The lower activation energy exhibited by a amylase from free Bacillus subtilis shows its efficacy over the a -amylase from immobilized Bacillus subtilis, owing to better spatial orientation and in addition an almost zero effect of external mass transfer resistance enjoyed by it.