Some approaches to improving the kinetic stability of malted African finger millet seed (Eluesine coracana) β-amylase

Studies were carried on the effect of some metallic chlorides at 50°C and the effect of pH at 60°C aimed at improving the kinetic thermostability of affinity purified β-amylase from malted and kilned African finger millet (Eluesine coracana) seed. The result of thermodynamic data kinetic stability show that the enzyme has preference for monovalent ions of Na⁺ and K⁺ to maintain thermostability while bivalent ions (Ca²⁺, Rb²⁺, Mg²⁺, Mn²⁺) could not prolong the initial phase of thermo inactivation, nor stabilize the thiol present in the active site and inability to form correct co-ordination geometry. The result showed that thermal stability is pH dependent. Eluesine coracana seed β-amylase was very stable at alkaline pH and neutral pH at higher temperature of 60°C but less stable at acidic pH of 5 and 6. Thermodynamic activation parameters derived from thermal activation data suggest the reaction to be faster at pH 6. The decrease in δS^≠ of thermo inactivation with increase in pH suggest the possible involvement of thiol and disulfide bridges in thermostability and also indicate hydrogen bond might play a role in stabilization of the enzyme at higher temperature in alkaline medium.