Effect of the stirring speed in the in vitro activity of α-amylase

Abstract

Amylases are one of the main enzymes used in industry for hydrolyzing starch molecules into simple sugar constituents, can be sourced from plants, animals and microorganisms. Starch converting α-amylase has applications in different industrial sectors, and an ongoing research topic is to improve processing conditions leading to enhanced enzymatic activity and lower processing costs. Surprisingly, there are basically no studies regarding the impact of stirring speed on α-amylase activity. In this work, the effect of stirring speed (0, 50, 250, 500, 1000 and 1500 rpm) on the hydrolysis of gelatinized corn starch dispersions (5 g starch dry basis/100 L) by pancreatic α-amylase (0.125 and 0.250 μg/mL) was studied. The analysis of the hydrolysis kinetics curves showed that relatively small stirring speeds had positive effect on the hydrolysis rate. This effect was likely caused by improvements in the mass transfer coefficient by virtue of increased flow velocities. However, the enzyme activity exhibited a negative trend for high stirring speeds. FTIR analysis of α-amylase subjected to stirring indicated that changes in the Amide I secondary structure might be behind the decreased hydrolysis at high stirring speeds. This short communication provides insights for enhancing the bio-conversion of starch by α-amylase via stirring speed mediation.