Optimization of human lysozyme production by Kluyveromyces lactis K7 in biofilm reactor

Lysozyme (1,4-β-N-acetylmuramidase) is a lytic enzyme, which degrades a constituent of bacterial cell wall. Lysozyme has been of interest in medicine, cosmetics, and food industries because of its anti-bactericidal effect. Several approaches for the production of human lysozyme have been reported. Kluyveromyces lactis is a suitable host cell for the production of human lysozyme, because it has effective secretory capacity and crabtree negative effect in fully oxidative conditions. K. lactis K7 is a genetically modified organism that expresses human lysozyme. There is a need to improve the human lysozyme production by K. lactis K7 to make the human lysozyme more affordable. The aim of this study was to determine the best plastic composite support (PCS) and optimize the growth conditions of K. lactis K7 for the human lysozyme production in biofilm reactor with PCS. The best PCS type was selected according to the biofilm formation on PCS (CFU/g) and human lysozyme production (Unit/ml). After determination of the best PCS in test tubes, a bioreactor equipped with a 2 L vessel was implemented. To find the optimum combination of growth parameters, three factors Box-Behnken design was used and different temperatures (20-40°C), pH (4-7), and aeration levels (0-1.5 volume of air/volume of broth/minute) were tested. As a result, the optimum temperature for biomass production was found higher than the optimum temperature for lysozyme production. Moreover, while biomass was higher at pH 6, the lysozyme production increased as pH decreased. The aeration caused increase in biomass, but decrease in lysozyme production.