Determining Mechanisms of Action and Optimum Use of Polyphenols As Food Preservatives

Lead Research Organisation: University of East Anglia
Department Name: Graduate Office


Preservatives are crucial ingredients in a wide range of foods which are present in order to control growth of pathogenic and spoilage organisms and maintain product quality and shelf life. A wide range of chemicals are currently used in this context including organic acids, salts and various nitrite compounds. Some of these additives, for example sodium and potassium nitrite, have potential health concerns1, 2 and there is great interest in industry in exploring alternatives3 which can retain antimicrobial activity but have a better safety profile. Polyphenols are a diverse group of natural products, extracted from plants which have multiple properties including antimicrobial activity4. Due to their perceived safety there has been great interest in using polyphenols as preservatives in various food stuffs5. Prosur is one commercially available polyphenol mixture currently being added to various foods or evaluated for incorporation in others. Despite the potential for polyphenols as antimicrobials there are major knowledge gaps regarding their mechanisms of action, spectrum of activity or potential bacterial resistance.

This project aims to identify active polyphenols from a well curated panel and determine their mechanisms of action and investigate how foodborne pathogens respond to polyphenol exposure. The ultimate goal is to inform development of improved polyphenol formulations to be used in food.

The project will incorporate analytical chemistry, microbiology and functional genomics to provide complementary approaches to these problems.


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Studentship Projects

Project Reference Relationship Related To Start End Student Name
BB/M011216/1 01/10/2015 30/09/2023
1801735 Studentship BB/M011216/1 01/10/2016 30/06/2022 Ryan Sweet
Title Listeria monocytogenes Membrane Permeability Assay SOP 
Description By taking advantage of the fluorescent properties of certain compounds (e.g.; Resazurin once internalised and metabolised by micro-organisms or Ethidium Bromide as it intercalates nucleic aids, usually restricted to the internal compartments of cells), one can quantify the capacity of tested compounds (Polyphenols, novel antimicrobials etc.) to permeabilise the outer-membranes/cell walls of, in this case, bacterial cells. While not a wholly novel method in and of itself, this method has been tweaked for the optimum use in Listeria monocytogenes, a psychotropic pathogen of some concern. Briefly; a 96-well plate is set up with the tested compound(s) and appropriate Negative and Positive Controls (For Positive Controls a known Efflux Pump Inhibitor which naturally enables the intracellular accumulation of various compounds is effective). The fluorescent indicator molecule (Resazurin or Ethidium Bromide; the latter in the case of Listeria) is added to all wells and finally a quantified bacterial suspension in Phosphate Buffered Saline (PBS) is added to each sample well (Excluding Blank wells used to normalise the fluorescence readings of the compounds/cells. These Blanks are instead inoculated with sterile PBS). The 96-well plate is then sealed with a transparent membrane and placed into a plate reader with the appropriate fluorescence filters and detectors. After an overnight run, measuring fluorescence and OD(600nm), the data is trimmed to an appropriate timeframe and can thus be utilised to quantify the effect of the tested compound(s) on the bacterial membrane/cell wall integrity of Listeria monocytogenes. 
Type Of Material Technology assay or reagent 
Year Produced 2020 
Provided To Others? No  
Impact This Research Method will enable other researchers to quantify the in vitro effect of experimental compounds on the bacterial cell wall/membrane integrity of Listeria monocytogenes; this will be particularly useful in the fields of Antimicrobial Resistance Mechanisms (ARM) elucidation and the coupled sector of novel antimicrobial research. 
Title Polyphenol Initial Screening Methodology 
Description A simple, quick and efficient 96-well screening method for the assaying of Polyphenol bioactivity vs. a micro-organism of choice. This assay is flexible in that it can be modified to test for the inhibitory activity of isolated polyphenols, and for the potentiative activity of polyphenols in conjunction with a known, efflux-pump ejected antibiotic (Chloramphenicol in this case). Assay relies on OD(600nm) measurements at the end-point of an incubation period (usually O/N). 
Type Of Material Technology assay or reagent 
Year Produced 2018 
Provided To Others? No  
Impact Assay was generated during the first year of my "new" project (i.e; after my transfer from the IFR's Peck Group to the QIB's Webber Group). Allows for a quick, efficient and middling-throughput initial screening of Polyphenols; used in this project to identifiy Polpyhenols with sufficient bioactvity to take through to the next stage of more detailed, quantitative screening. 
Description Norwich Science Fair, Staffing a QIB Stand on Biocides, Antimicrobials and Antimicrobial Resistance 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Myself and the Webber Research Group manned a stand at the annual Norwich Science Fair at The Forum. Our stall was designed to educate the general public about biocides, antimicrobials and their overuse, antimicrobial resistance and for my particular part the potential of plant-based polyphenols as substitutes for the above. We engaged with well over 500+ members of the general public, many of which were young school children, to educate them about the appropriate use of biocides/antimicrobials and to hopefully inspire young children towards a career in scientific research.
Many members of the public left feedback after attending our stall, all of which was positive and complimentary in nature. Children in particular seemed to enjoy our stall and its' accompanied activities.
Year(s) Of Engagement Activity 2018
Description Poster Presentation: BSAC ARM Workshop, Birmingham Nov. 2019. 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact The British Society of Antimicrobial Chemotherapy's Antimicrobial Resistance Mechanisms (BSAC ARM) Workshop, held in Birmingham in 2019, was a conference intended to bring together scientists and students from around the UK, and potentially further, to discuss and present novel and current research within the fields of antimicrobial resistant epidemiology, antimicrobial resistance mechanisms and the development of novel antimicrobial substitutes (Analogues of presently used antibiotics, substitute compounds such as polyphenols etc.).
While attending this 1-2 day event, I networked and discussed ideas surrounding experimental design, potentially untapped mines of novel compounds, etc., with experts in the field and with current students. I also presented a poster detailing a section of my work studying the capacity for polyphenols (Secondary plant metabolites) to disrupt bacterial membranes and synergise with currently used antibiotics. This poster gained much attention and sparked a plethora of discussion.
Year(s) Of Engagement Activity 2019