Identification of antimicrobial peptides capable of reducing biofilm growth in seawater desalination processes

Seawater desalination is most commonly done today by reverse osmosis (RO) using thin-fi lm composite membranes. A major problem in RO desalination is biofouling, caused by adhesion and growth of bacteria to form biofi lm on the membrane surface.Recently we proposed a new approach to reduce biofi lm formation on RO membranes that is based on immobilization of antimicrobial peptides (AMPs) onto the membrane surface. In this study we screen AMPs capable of reducing biofi lm growth under conditions simulating seawater desalination, and search for mode of binding to the membrane without affecting the peptides bioactivity. A specifi c bioassay was developed for screening peptides activity in high salinity conditions in order to evaluate the inhibition of biofi lm growth, based on growing biofi lm-forming bacteria in a 96-wells microtiter plate. We prepared various AMPs known from the literature by solid phase peptide synthesis (SPPS) using Fmoc-chemistry. The bactericidal activity of AMPs was examined in fresh water and compared to high salinity water. Most AMPs lost their activity in high salinity conditions; yet, few peptides possessed their bactericidal activity and were used in subsequent experiments. Searching for mode of linkage was performed by evaluating the bactericide activity of AMPs modifi ed with numerous types of linker molecules. Based on literature studies that showed no decrease in bactericidal activity of AMPs upon N-terminal modifi cation, we prepared the corresponding peptides with modifi ed spacers on their amino-terminal and evaluated their antimicrobial activity in solution. Indeed, we obtained Gly3-spacersthat retained activity, which were used subsequently as linkers to RO membranes. The mode of binding, as well as bactericide activity of the peptides and of the membranes will be presented and discussed.This study will lay the bases for a novel approach to decrease biofi lm formation on the surface of RO membranes during RO desalination.