Catalytic, kinetic and thermal properties of free andimmobilized Bacillus subtilis -MK1 α-amylase on Chitosan-magnetic nanoparticles

Samia A Ahmed; Mohamed A A Abdella; Gamal M El-Sherbiny; Atef M Ibrahim; Aliaa R El-Shamy; Sherien M M Atalla; Mohamed E Hassan

doi:10.1016/j.btre.2020.e00443

Catalytic, kinetic and thermal properties of free andimmobilized Bacillus subtilis -MK1 α-amylase on Chitosan-magnetic nanoparticles

Biotechnol Rep (Amst). 2020 Feb 26:26:e00443. doi: 10.1016/j.btre.2020.e00443. eCollection 2020 Jun.

Authors

Samia A Ahmed¹, Mohamed A A Abdella¹, Gamal M El-Sherbiny², Atef M Ibrahim³, Aliaa R El-Shamy¹, Sherien M M Atalla¹, Mohamed E Hassan^{1

4}

Affiliations

¹ Chemistry of Natural and Microbial Products Department, National Research Centre, Dokki, Cairo, Egypt.
² Department of Botany and Microbiology, Faculty of Science (Boys), Al-Azhar University, Cairo, Egypt.
³ Microbial Biotechnology Department, Genetic Engineering and Biotechnology Research Institute (GEBRI), University of Sadat City, Menoufia, Egypt.
⁴ Centre of Excellence, Encapsulation Nanobiotechnology Group, National Research Centre, Dokki, Cairo, Egypt.

Abstract

Bacillus subtilis strain-MK1 α-amylase was successfully immobilized on Chitosan-magnetic nanoparticles (Ch-MNP) that had been modified with polyethyleneimine (PEI) and glutaraldehyde (GA). Optimization of Ch-MNP/PEI/GA beads modification by Central Composite design enhanced the immobilization yield (IY %) by 1.5-fold. Ch-MNP/PEI/GA was characterized before and after modification and immobilization by FTIR and SEM. Ch-MNP/PEI/GA/Enzyme showed the same pH optima of free enzyme, while an elevation 10 °C in temperature optima was observed after its immobilization. Ch-MNP/PEI/GA/Enzyme displayed higher Km and Vmax values (2.1 and 1.2-fold) and lower Vmax/Km ratio (1.7-fold), respectively than the free enzyme. Compared to the free enzyme, Ch-MNP/PEI/GA/Enzyme exhibited lower activation energy, lower deactivation constant rate, higher D-values, higher half-life, and higher energy for denaturation. Immobilization of α-amylase increased enthalpy (4.2-fold), free energy (1.1-fold) and decreased entropy (4.6-fold) of thermal inactivation. A significant increase in pH stability of Ch-MNP/PEI/GA/Enzyme was observed especially at alkaline pH values. In addition, Ch-MNP/PEI/GA/Enzyme preserved 83.2 % of its initial activity after 15 consecutive cycles. When storing Ch-MNP/PEI/GA/Enzyme at 4 °C the residual activity was 100 and 86 %, respectively after 21 and 40 days. Finally, immobilization process improved the catalytic properties and stabilities, thus raising the suitability for industrial processes with lower cost and time.

Keywords: Catalytic; Chitosan-magnetic nanoparticles; Immobilization; Kinetics; Thermodynamics; α-amylase.