Human Lysozyme Production by Kluyveromyces lactis K7 in Fed-Batch and Continuous Biofilm Reactors

Lysozyme (1,4-β-N-acetylmuramidase) is a lytic enzyme, which degrades a constituent of bacterial cell wall. It has been used in pharmaceutical and food industries. Nowadays, egg white is the commercial source of lysozyme. However, egg-white lysozyme may cause immunological problems when used by humans who have allergies to eggs. Therefore, use of human lysozyme in industry is safer than the use of egg-white lysozyme. In this study Kluyveromyces lactis K7 and biofilm reactor with plastic composite support were used to produce human lysozyme. Biofilm reactors cause increase in cell density in the reactor and different fermentation strategies may help to prevent substrate and product inhibitions.  In our previous study, we have demonstrated that biofilm reactors can improve human lysozyme production in batch fermentation. Furthermore, this study was undertaken to enhance the production by application of fed-batch, and continuous fermentation modes in biofilm reactor. Overall, the human lysozyme production by K. lactis K7 was 110 U/ml in suspended-cell batch fermentation while application of batch fermentation in biofilm reactor yielded 173 U/ml, which was then increased to 187 U/ml by fed-batch fermentation. Moreover,  although there wasn’t a significant increase in the production level in continuous fermentation (136 U/ml), significantly higher production rate in continuous fermentation (7.5 U/ml/h) was achieved at the optimum dilution rate (0.055 h^-1) when compared to batch fermentation in biofilm (4 U/ml/h) (p<0.05). This study clearly demonstrated that fed-batch and continuous fermentations can be used to improve human lysozyme production by K. lactis K7.