Impact of industrial stress factors on lysozyme enzyme: Role of denaturation processes and initial protein activity

Abstract

Protein instability and efficiency loss are the major drawbacks industry faces in medical, pharmaceutical and food sectors. Understanding how processes induce denaturation and consequently modify enzymatic activity can lead to more sustainable pharmaceutical or food manufacturing by avoiding the loss of active molecules. In the present investigation, the influence of some stress factors (heating, chemical denaturation, ultrasound application, and ultrafiltration) on the final lysozyme antibacterial activity was evaluated to determine the limiting conditions of industrial processes. Two commercial lysozymes with different initial enzymatic activities were compared. The temperature of denaturation was higher than 70 °C, and a reduction of 25% of activity was observed after treatment at 90 °C. Chemical denaturants (urea and guanidine hydrochloride) induced different LSZ conformational changes, and the modification was dependent on the concentration for guanidine hydrochloride (activity decrease of 30% using a concentration of 10 M). The difference between the two lysozymes was observed for the ultrasound and ultrafiltration treatments. During ultrasonic treatment, one lysozyme was stable for 15 min, while a loss of activity was observed after 3 min for the other. The same difference in stability was observed during ultrafiltration process. The activity decreases linearly with transmembrane pressure (around 50% for 12 bar) during filtration of the less stable lysozyme, and no change in the antibacterial activity was observed for the second protein. This study shows that stress factors induce different denaturation states and that for some of them (ultrasound and ultrafiltration), the presence of small residues in the protein formulation is important.