Food grade antimicrobial peptides as alternatives to chemical preservatives to extend the shelf life of food products

Microbes are responsible for both food spoilage and toxicity, the first being the cause of food losses and waste, the second producing food poisoning episodes worldwide, compromising the human health and safety. Food producers are therefore looking for biological substitutes to be used instead of chemical food preservatives and that can represent a valid alternative for the biopreservation of food products. Antimicrobials of plant, animal and microbial origin have demonstrated to limit oxidation, discoloration and to elongate the shelf life meanwhile ensuring food safety. Particularly, antimicrobial peptides (AMPs) are considered a new interesting strategy to be applied in food control for their low toxicity (even more if they derived from edible plants), selectivity and stability. They are generally based on 10-50 amminoacids, and harbour a general positive charge, disulphide bonds, hydrophobic residues and the capacity to target the cell outer membrane, with the formation of pore channels. AMPs use in food preservation is still to be evaluated and needs further demonstration, most of all for the limitation of large-scale synthesis. Another aspect to be tested is the AMPs specificity when added to food, the possible interactions with other microorganisms present in the same food matrix, their stability when extrinsic factors or control measures are applied in food processing and the possible reactions with the food ingredients.

Antimicrobial peptides, derived from bean and tomato proteins, have been identified and characterised for their relevant antibacterial and antifungal action, without cytotoxic action on human cells. The peptides have been also selected for their ability to inhibit in lab-scale foodborne pathogenic bacteria (e.g. Listeria monocytogenes, Bacillus cereus, E. coli, Clostridium botulinum, Salmonella) and provide a protection against spoilage microbiota such as Pseudomonas, Enterobacteriaceae, yeasts and moulds. The work will be aimed to express these AMPs in cell models (E. coli, Pichia pastoris) to obtain large quantities to be used in pilot scale experiments. This will allow to identify the dose/response relationship and the best protection effect. Different peptide combinations/concentration will be optimised. Control of foodborne pathogens will be considered in specific challenge studies. Testing of the best performing peptides in industrial conditions using experimental approaches designed to provide quantitative data to determine a statistically significant shelf-life increase, spoilage reduction and pathogens control, together with the maintenance of the original organoleptic quality of the product.

The reduction rate of pathogenic/spoilage microorganisms by the use of a known dose of AMP will be evaluated; the durability of AMP in different food matrices will be also considered, such as the potential toxicity at the concentration of use and the interference with other food ingredients. The main objectives of this study will be to report about  in vitro antimicrobial activities of AMPs, their production and quantification using heterologous systems of expression, antimicrobial activities of AMPs in food models against the pathogenic/spoilage microorganisms at risk and testing of the most promising AMPs (and combinations) in pilot scale productions.