Određivanje parametara stresa kod bakterije Listeria innocua nakon tretmana plazmom

master's thesis

• Title (english): Determination of stress parameters in bacteria Listeria innocua after plasma treatment
• Author: Tihana Žugčić
• Mentor: Anet Režek Jambrak (mentor)
• Granter: University of Zagreb; Faculty of Food Technology and Biotechnology; (Department of Food Engineering); (Laboratory for Food Processes Engineering); Zagreb
• Defense date and country: 2018-07-05, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Food Technology

Abstract

Svrha ovog rada je proučiti odgovor bakterije Listeria innocua ATCC 33091 na stres izazvan tretmanom hladnom plazmom. Uzorci bakterijske suspenzije tretirani su tekućinskom plazmom u mjehurićima argona. Promatran je utjecaj plazme na stopu redukcije, revitalizaciju, koncentraciju slobodnih radikala, istjecanje unutarstaničnog sadržaja te stvaranje biofilma. Uzorci su tretirani uz tri nezavisne varijable: vrijeme izloženosti plazmi (5 i 10 min), frekvencija (60, 90 i 120 Hz) i polaritet (pozitivan i negativan). Rezultati su analizirani metodom odzivne površine (RSM) koristeći program STATGRAPHICS Centurion. Pri pozitivnom polaritetu, uz frekvenciju od 90 Hz postignuta je potpuna inaktivacija bakterijskih stanica nakon 5 minuta tretmana te najviši stupanj redukcije (6,25 log10 CFUmL-1). Najveći porast koncentracije radikala je pri pozitivnom polaritetu, uz frekvenciju od 120 Hz i 10 minuta tretiranja. Najznačajnija redukcija stvaranja biofilma (90,05 %) postignuta je nakon 10 minuta tretmana, pri pozitivnom polaritetu i 120 Hz. Bolja inaktivacija postignuta je pri pozitivnom polaritetu, dok je pri negativnom polaritetu postignut manji postotak revitalizacije, iako je kod svih tretiranih uzoraka došlo do revitalizacije stanica nakon inkubacije od 24 sata.

Abstract (english)

The aim of this work is to analyze bacterial behavioral responses of Listeria innocua ATCC 33091 on the creation of stress parameters after cold plasma treatment. Samples of the bacterial suspension were treated by plasma generated in bubbles of argon immersed in liquid. The influence of cold plasma on the degree of reduction and recovery of Listeria innocua ATCC 33091, the leakage of intercellular content, free radical concentration and formation of biofilm were determined. The samples were treated using three independent variables: exposure time to plasma (5 and 10 min), frequency (60, 90 and 120 Hz) and polarity (positive and negative). The results were analyzed using the STATGRAPHICS Centurion program and results were represented by response surface methodology (RSM). Complete inactivation was achieved at the positive polarity, frequency of 90 Hz and 5 minutes treatment. The highest increase in free radical concentration was at positive polarity, 120 Hz and 10 minutes treatment. The best effect on reduction of biofilm formation (90,05 %) is achieved after 10 minutes, at positive polarity and 120 Hz. The results showed better inactivation at positive polarity and reduced recuperation at negative polarity. All the samples were recovered after the incubation period of 24 hours.

• Keywords: hladna plazma; Listeria innocua; inaktivacija; revitalizacija; parametri stresa
• Keywords (english): cold plasma; Listeria innocua; inactivation; recovery; stress parameters
• Language: croatian
• URN:NBN: urn:nbn:hr:159:805199
• Study programme: Title: Food Engineering; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka prehrambenog inženjerstva (magistar/magistra inženjer/inženjerka prehrambenog inženjerstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2019-11-28 10:44:34