Effect of non aqueous solvent on structural stability of α-amylase: A cost-effective prospective for protein stabilization

The aim of the present study is to assess the effect of non-aqueous organic solvent on structural stability, molecular integrity and structure of α-amylase. The activity and thermal stability of the enzyme was measured before and after treatment with non polar solvent (i.e. hexane). The activity was found to be marginally affected and thermal stability was found to be significantly increased after treatment with hexane. The enzyme was found to be more resistant to thermal inactivation in hexane compared to in an aqueous buffer. The fluorescence measurement indicated a blue shift of 3 nm in the emission maximum (λmax) probably due to a minor change in the polarity of aromatic amino acid residues after treatment with a non-aqueous solvent. Assessment of thermal denaturation profile, 1-anilino-8-naphthalene-sulfonate (ANS) binding and acrylamide quenching of the enzyme suggested an increase in the molecular integrity and overall stability of the enzyme after treatment with hexane. However, these entire molecular events were not accompanied by any major change in the secondary structure. Our findings suggest that treatment of proteins or enzymes in non-aqueous solvents could be an attractive and cost-effective strategy to improve their structural stability without compromising their biological functions.