Affinity tag effect on the salt rejection potential of Halomonas elongata aquaporin incorporated in thin film nanocomposite membrane

Abstract

In this study, effect of affinity tags, Histidine (His) and Glutathione-S-Transferase (GST), on the activity of halophilic aquaporin was analyzed. The gene coding for H. elongata aquaporin was cloned into pET28a vector and expressed in E. coli BL21 successfully. Stopped flow light scattering measurements showed that His-tagged aquaporin is functional. The difference in the filtration parameters caused by affinity tags were determined by using thin film composite nano-filtration (NFC) membranes prepared with the aquaporins. At 100 mM salt concentration, water permeability (L/m2.h) and the % salt rejection of NFC membranes produced with the His-tagged aquaporin was found to be higher than that of the membrane with GST-tagged aquaporin. Salt rejection of His-tagged aquaporin-membrane was found to be 53% with a lower solute permeability value (B). Use of short affinity tag (His tag) for cloning resulted in higher solute rejection ability of TFC membranes prepared with H. elongata aquaporins.