Gum tragacanth for immobilization of Bacillus licheniformis protease: Optimization, thermodynamics and application

Abstract

A proficient covalent immobilization support was concocted and utilized to immobilize the Bacillus licheniformis protease (BPR) after the functionalization of gum tragacanth-agar (GT-agar) discs with polyethyleneimine (PEI) and glutaraldehyde (GA). The functionalization scheme was honed with Box-Behnken design (BBD) in order to acquire the upmost immobilized BPR (iBPR) activity. The optimum functionalization scheme comprised treating the discs with 0.5% PEI at pH 9.1 followed by their immersion in a 0.2% GA solution. The functionalization scheme was monitored via EDX, FTIR, and SEM analysis. The optimally functionalized GT-agar disks immobilized BPR with 82.79% expressed activity and 35.51% immobilization yield. The pH profile, temperature profile, and thermal stability of the free and immobilized BPR (iBPR) were compared. The heightened thermal stability of the iBPR was verified from its kd, t1/2, D-values, ΔH, and ΔS values. For instance, the t1/2 and D-values offered by the iBPR at 59 °C were 4.8 fold loftier than those offered by the free BPR. The iBPR reusability was then inspected, and 52.85% activity was kept after 10 reusability cycles when the 0.1 M pH 10.2 buffer was adopted. Finally, the iBPR was utilized to hydrolyze soy protein isolate (SPI). The effect of the reaction time on the SPI degree of hydrolysis (DH) and on the DPPH scavenging capability of the procured hydrolysates was investigated. Both the SPI-DH and the DPPH scavenging were incremented with time, and a maximum 16.56% DH and 50.78% DPPH scavenging were recorded after 24 h.