Lisa Purk
About
My research project
Biofilm formation of Listeria monocytogenes on a novel triphasic viscoelastic food model and the application of a novel mild preservation technique; cold plasmaListeria monocytogenes is one of the rising pathogenic threats in food industry because of its characteristics. This bacterium is able to grow at refrigerating temperatures and it is a biofilm former. These abilities makes the bacterium more persistent and more resistance in its environment. Especially its behaviour on viscoelastic biotic surfaces are not very well studies in literature. Therefore my project focusses on the behaviour and biofilm formation of L. monocytogenes on a triphasic viscoelastic food model.
Another contributing factor is that food industries are trying to find new preservation techniques which do not interact or change the food itself. One novel technology complying with these demands is cold plasma. Cold plasma is known to have antibacterial and antibiofilm properties. The novelty for my project is the application of cold plasma on a biotic surface with L. monocytogenes biofilms and the combination with different co-cultures or with the addition of other natural antimicrobials; like nisin.
Supervisors
Listeria monocytogenes is one of the rising pathogenic threats in food industry because of its characteristics. This bacterium is able to grow at refrigerating temperatures and it is a biofilm former. These abilities makes the bacterium more persistent and more resistance in its environment. Especially its behaviour on viscoelastic biotic surfaces are not very well studies in literature. Therefore my project focusses on the behaviour and biofilm formation of L. monocytogenes on a triphasic viscoelastic food model.
Another contributing factor is that food industries are trying to find new preservation techniques which do not interact or change the food itself. One novel technology complying with these demands is cold plasma. Cold plasma is known to have antibacterial and antibiofilm properties. The novelty for my project is the application of cold plasma on a biotic surface with L. monocytogenes biofilms and the combination with different co-cultures or with the addition of other natural antimicrobials; like nisin.
Publications
The aim of the current study is to develop and characterise novel complex multi-phase in vitro 3D models, for advanced microbiological studies. More specifically, we enriched our previously developed bi-phasic polysaccharide (Xanthan Gum)/protein (Whey Protein) 3D model with a fat phase (Sunflower Oil) at various concentrations, i.e., 10%, 20%, 40% and 60% (v/v), for better mimicry of the structural and biochemical composition of real food products. Rheological, textural, and physicochemical analysis as well as advanced microscopy imaging (including spatial mapping of the fat droplet distribution) of the new tri-phasic 3D models revealed their similarity to industrial food products (especially cheese products). Furthermore, microbial growth experiments of foodborne bacteria, i.e., Listeria monocytogenes, Escherichia coli, Pseudomonas aeruginosa and Lactococcus lactis on the surface of the 3D models revealed very interesting results, regarding the growth dynamics and distribution of cells at colony level. More specifically, the size of the colonies formed on the surface of the 3D models, increased substantially for increasing fat concentrations, especially in mid- and late-exponential growth phases. Furthermore, colonies formed in proximity to fat were substantially larger as compared to the ones that were located far from the fat phase of the models. In terms of growth location, the majority of colonies were located on the protein/polysaccharide phase of the 3D models. All those differences at microscopic level, that can directly affect the bacterial response to decontamination treatments, were not captured by the macroscopic kinetics (growth dynamics), which were unaffected from changes in fat concentration. Our findings demonstrate the importance of developing structurally and biochemically complex 3D in vitro models (for closer proximity to industrial products), as well as the necessity of conducting multi-level microbial analyses, to better understand and predict the bacterial behaviour in relation to their biochemical and structural environment. Such studies in advanced 3D environments can assist a better/more accurate design of industrial antimicrobial processes, ultimately, improving food safety.