Study of the relationship between applied transmembrane pressure and antimicrobial activity of lysozyme

During the processing of biomolecules by ultrafiltration, the lysozyme enzyme suffers conformational changes, which can affect its antibacterial activity. Operational conditions are considered ones of the principal responsible for the modifications, especially when using the same membrane and molecule. The present study demonstrates that, the same cut-off membrane (commercial data) can produce different properties on the protein after filtration, due to their different pore network. The filtration of lysozyme, regardless of the membrane, produces a decrease in the membrane hydraulic permeability (between 10–30%) and an increase in its selectivity in terms of observed rejection rate (30%). For the filtrated lysozyme, it appears that the HPLC retention time increases depending on the membrane used. The antibacterial activity of the filtrated samples is lower than the native protein and decreases with the increase of the applied pressure reaching 55–60% loss for 12 bar which is not reported in the literature. The observed results by SEC-HPLC and bacteriological tests, suggest that the conformation of the filtrated molecules are indeed modified. These results highlight the relationship between protein conformation or activity and the imposed shear stress.