Comparison of continuous fermentations in biofilm and suspended-cell bioreactors for production of human lysozyme

Lysozyme is a lytic enzyme, which has antimicrobial activity. It has been used for food and pharmaceutical applications. Lysozyme production needs to be enhanced to meet its current demand in the industry, because currently egg is used for commercial lysozyme production and it poses immunological problems and it is four-times less effective than human lysozyme. In our earlier study, biofilm reactors have been evaluated for human lysozyme production by Kluyveromyces lactis K7 in batch fermentation, which demonstrated significant improvement in production of human lysozyme. Therefore, this study was undertaken to evaluate continuous fermentations for the human lysozyme production by K. lactis K7 in biofilm reactor and compare with continuous fermentation in suspended cell bioreactor. For this purpose, continuous fermentation was conducted at different dilution rates (0.03-0.08 h^-1) in both biofilm and suspended cell reactors. As a result, biofilm reactor provided significantly higher productivity (7.5 U/ml/h) with 0.0055 h^-1 of dilution rate compared to the maximum productivity in suspended-cell bioreactor (4 U/ml/h) with 0.004 h^-1 of dilution rate. In conclusion, biofilm reactors provided operation at higher dilution rates because of the immobilized cells compared to suspended cell reactor.