Biocatalytic action of proteases in ionic liquids: Improvements on their enzymatic activity, thermal stability and kinetic parameters

This study evaluated the effect of the addition of the following ionic liquids (IL): choline chloride (CC), tetramethylammonium bromide (TB) and 1 ethyl 3 methylimidazolium bromide (EM), on some biochemical properties including enzymatic activity and different kinetic parameters of commercial proteases. The enzyme IL combinations that showed the highest increases in enzyme activities were as follows: CC (0.5 mM) and Neutrase 0.8 L; CC (5 mM) and Flavourzyme (R) 500 L; TB (2000 mM) and Alcalase (R) 2.4 L, with relative increases of 20, 15 and 150% in protease activities, respectively, compared to the control assays. The combination TB and Alcalase (R) 2.4 L showed a reduction of 50% of the activation energy (E-a), an increase of the relation V-max/K-m of 35% and a 16-fold rise in the values of t(1/2), and D. Neutrase (R) 0.8 L combined with CC showed an increase of 20% in the relation V-max/K-m. The combination Flavourzyme (R) 500 L and CC presented a 20% higher value of the relation V-max/K-m and a 2-fold increase in the values of t(1/2) and D compared to the control assay. In summary, the most positive effects observed in this study included proteases with improved activity and stability properties and a greater affinity for the substrate. (C) 2018 Elsevier B.V. All rights reserved.