Katie Costello

Dr Katie Costello

Lecturer
MEng Chemical Engineering, PhD Chemical Engineering
+44 (0)1483 682130
23 BC 02
Monday to Friday, 8am - 5pm

Academic and research departments

Department of Chemical and Process Engineering.

Research

Research interests

Courses I teach on

Undergraduate

My publications

Publications

Costello Katie, Gutierrez-Merino Jorge, Bussemaker Madeleine, Ramaiolia M, Baka M, Van Impe J, Velliou Eirini (2018) Modelling the microbial dynamics and antimicrobial resistance development of Listeria in viscoelastic food model systems of various structural complexities, International Journal of Food Microbiology 286 pp. 15-30 Elsevier
DOI: 10.1016/j.ijfoodmicro.2018.07.011
Minimal processing for microbial decontamination, such as the use of natural antimicrobials, is gaining interest in the food industry as these methods are generally milder than conventional processing, therefore better maintaining the nutritional content and sensory characteristics of food products. The aim of this study was to quantify the impact of (i) structural composition and complexity, (ii) growth location and morphology, and (iii) the natural antimicrobial nisin, on the microbial dynamics of Listeria innocua. More specifically, viscoelastic food model systems of various compositions and internal structure were developed and characterised, i.e. monophasic Xanthan gum-based and biphasic Xanthan gum/Whey protein-based viscoelastic systems. The microbial dynamics of L. innocua at 10oC, 30oC and 37oC were monitored and compared for planktonic growth in liquid, or in/on (immersed or surface colony growth) the developed viscoelastic systems, with or without a sublethal concentration of nisin. Microscopy imaging was used to determine the bacterial colony size and spatial organisation in/on the viscoelastic systems. Selective growth of L. innocua on the protein phase of the developed biphasic system was observed for the first time. Additionally, significant differences were observed in the colony size and distribution in the monophasic Xanthan gum-based systems depending on (i) the type of growth (surface/immersed) and (ii) the Xanthan gum concentration. Furthermore, the system viscosity in monophasic Xanthan gum-based systems had a protective role against the effects of nisin for immersed growth, and a further inhibitory effect for surface growth at a suboptimal temperature (10oC). These findings give a systematic quantitative insight on the impact of nisin as an environmental challenge on the growth and spatial organisation of L. innocua, in viscoelastic food model systems of various structural compositions/complexities. This study highlights the importance of accounting for system structural composition/complexity when designing minimal food processing methods with natural antimicrobials.
Costello Katherine M., Gutierrez-Merino Jorge, Bussemaker Madeleine, Smet Cindy, Van Impe Jan F., Velliou Eirini G. (2020) A multi-scale analysis of the effect of complex viscoelastic models on Listeria dynamics and adaptation in co-culture systems, AIChE Journal 66 (1) e16761 Wiley
DOI: 10.1002/aic.16761

Natural antimicrobials are of interest to replace traditional food decontamination methods: they are milder and maintain desirable sensory characteristics. However, efficacy can be affected by food structure/composition, thus structural effects in a co-culture pathogen/microflora system are investigated. Listeria was grown planktonically (liquid broth) or on a biphasic viscoelastic system, in monoculture with/without artificial nisin, or in co-culture with L. lactis (nisin/non-nisin producing). Microbial growth kinetics were monitored and advanced microscopy techniques were utilised to quantify cellular interactions and spatial organisation.

Microstructural effects are observed on the kinetics, with differences in monoculture/co- culture. Significant microscopic differences are observed in spatial organisation and colony size. We are the first to observe changing growth location for all species in monoculture/co- culture, with differences in colony size/organisation through stationary phase. This study provides insight into the environmental stress response/adaptation of Listeria grown on structured systems in response to L. lactis and natural antimicrobials.