טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentTali Rydlo
SubjectAntimicrobial Peptides in Food Model Systems: Structure-
Activity Relationships Studies
DepartmentDepartment of Biotechnology and Food Engineering
Supervisor Full Professor Mor Amram


Abstract

Over the years, consumers increasingly demand more natural, preservative-free and minimally processed foods. Also, worldwide concern regarding antimicrobial resistance and diseases outbreaks caused by food-related pathogens have created the need to develop new, efficient and natural classes of antimicrobial agents.

Here, a frog-derived antimicrobial peptide (dermaseptin S4) and its synthetic derivatives - that varied with respect to length, hydrophobicity and charge - were investigated against the food related pathogen, Escherichia coli O157:H7 under extreme incubation conditions relevant to food products.

A 28-mer analog displayed potent inhibitory activity and rapid bactericidal kinetics at high salt concentrations, acidic or basic conditions and extreme temperatures. Its N-terminal 14-mer derivative (P14) maintained high potency only within a narrow range of incubation conditions, pointing to the importance of the hydrophobic C-terminal domain of the full-length peptide.

Potency range was re-extended upon conjugation of fatty acids to P14. Namely, one of the resulting lipopeptides (NC12-P14) was more potent and affected bacterial viability under most of the conditions tested, including in commercial apple juice.

Mechanistic implications of peptides’ secondary structure and binding properties to an idealized membrane were probed using circular dichroism and surface plasmon technology, respectively. Our findings suggest that inefficiency is not linked to structure alterations. Rather, inefficiency is linked to peptide’s difficulty in penetrating the hydrophobic core of the target membrane at acidic conditions.


 Overall, the data emphasizes the importance of hydrophobicity and net charge on peptide activity, especially under extreme incubation conditions. Moreover the study is indicative of a certain potential for use of dermaseptin and its derivatives in food safety, namely with respect to fighting multi-drug resistant pathogens.