Restriction lift date: 2022-09-30
A study on the application of synthetic antimicrobial peptides derived from plants for the reduction of yeast spoilage in food
Shwaiki, Laila N.
University College Cork
Food spoilage caused by the undesirable growth of microorganisms contributes to the crisis of food waste and food loss worldwide. Bacterial and fungal microorganisms can grow and spread in food, resulting in the spoilage of many food products intended for human consumption. Food preservatives and various preservation techniques that have been developed of decades within the food industry aim to slow the rate of food spoilage, therefore increasing the shelf-life of food products and control the level of food waste. Although preservatives have been successful in reducing spoilage and associated food waste, spoilage microbes persist, reducing the quality of food, making them inedible and further contributing to food waste. In recent decades there has been an increasing demand from consumers for food products that contain less chemicals and more “natural” forms of food preservatives. The use of antimicrobial peptides (AMPs) for this purpose is the basis for the research that was performed in this thesis. Plants produce AMPs as part of their immune system, possessing strong antimicrobial activity. This thesis aims to explore the antimicrobial activity of various plant AMPs that have been synthesised and tested for their inhibitory activity against food spoilage yeast. A literature review is presented in chapter 2, that explores the diversity of plant AMPs, their spectrum of activity, and their potential as novel food preservatives. Chapter 3 reviews the potential of synthetic modified peptides for the purpose of reducing food waste through their use as novel preservative agents in food. Two different families of plant AMPs have been examined for their antiyeast activity against common food spoilage yeasts in chapters 4, 5 and 6. Chapter 4 and 5 investigate three AMPs (radish peptides Rs-AFP1, Rs-AFP2 and barley peptide D-lp1) from the family of plant defensins, as well as their characteristics (mechanism of action, safety, stability) and applicability in various food products to reduce the growth of spoilage yeast. Both radish defensins were successful in reducing the growth of the yeast, with Rs-AFP2 proving more effective. The barley defensin showed higher antiyeast activity than the radish peptides. All three peptides were successfully incorporated into various food matrices, supporting and serving as a proof of concept for their potential use as novel food preservative agents. A different family of plant AMPs (snakin) was studied in chapter 5 to examine its potential as a food preservative, and to gain an understanding of the properties and characteristics that peptides deriving from different families of plant AMPs may have (defensin versus snakin peptides). The snakin peptide originated from potato tubers, and although was demonstrated to reduce the growth of the yeast and to have potential in different beverage matrices, it was less effective than the defensin peptides. Chapter 7 explores the antiyeast activity of a peptide (KK-14) whose sequence was designed based on known characteristics of plant AMPs that have been associated with antimicrobial activity. This peptide was further modified to generate three peptide derivatives. These derivatives displayed stronger activity against the yeast than the original KK-14 peptide and could be regarded as a potential food preservative. The thesis discussion also explores the various factors that must be considered in any discussion around the potential and future use of synthesised peptides as novel food preservative agents.
Antimicrobial peptides , Synthetic peptides , Food spoilage yeast , Antiyeast assays , Plant antimicrobial peptides , Defensins , Snakin
Shwaiki, L. N. 2021. A study on the application of synthetic antimicrobial peptides derived from plants for the reduction of yeast spoilage in food. PhD Thesis, University College Cork.