Primjena visokonaponskoga električnoga pražnjenja na inaktivaciju mikroorganizama

doctoral thesis

• Title (english): Application of electrical discharge plasma on inactivation of microorganisms
• Author: Višnja Stulić
• Mentor: Zoran Herceg (mentor); MBZ: 25481543920
• Committee member: Višnja Bačun-Družina (predsjednik povjerenstva)
• Granter: University of Zagreb; Faculty of Food Technology and Biotechnology; (Department of Process Engineering); Zagreb
• Defense date and country: 2018-12-12, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Food Technology
• Universal decimal classification (UDC): 612 - Physiology

Abstract

Cilj ovog rada bio je ispitati utjecaj tretmana plinskom plazmom i tekućinskom plazmom u mjehurićima na inaktivaciju 7 mikroorganizama u stacionarnoj i eksponencijalnoj fazi rasta (Escherichia coli MG1655-K12, Salmonella enterica serotip Typhimurium LT21, Listeria innocua ATCC 33091, Staphylococcus aureus 3048, Bacillus cereus 30, Rhodotorula spp 74 i Saccharomyces cerevisiae ATCC 204508). Analizirani su fizikalno-kemijski parametri, revitalizacija stanica nakon tretmana, istjecanje unutar staničnog sadržaja, odgovor stanica na stres i formiranje biofilma. Dizajniran je eksperiment s tri različite varijable (frekvencija: 60, 90, 120 Hz, vrijeme: 5' i 10', plin: zrak i argon) kako bi se utvrdili optimalni uvjeti tretmana pomoću dva tipa reaktora pri pozitivnom polaritetu i provodljivosti medija od 100 μS cm-1. Potpuna inaktivacija u stacionarnoj fazi rasta postignuta je kod oba tipa reaktora te svih mikroorganizama, osim za kvasac Rhodotorula spp. U eksponencijalnoj fazi rasta potpuna inaktivacija tretmanom tekućinskom plazmom u mjehurićima u argonu postignuta je kod 4 mikroorganizma: S. enterica, L. innocua, S. aureus i S. cerevisiae. Iako su rezultati analize istjecanja staničnog sadržaja pri 260 i 280 nm pokazali istjecanje DNA i proteina, analizom revitalizacije stanica dokazan je oporavak stanica. Tekućinska plazma u mjehurićima pri uvjetima tretmana (90 Hz, 10', argon) pokazala se kao najučinkovitiji tretman te je isti odabran za analizu proteoma odabranih mikroorganizama u stacionarnoj fazi rasta: E. coli, L. innocua i S. cerevisiae i analize trasmisijskim elektronskim mikroskopom (TEM). Proteomskim analizama provedenim pomoću MALDI-TOF/TOF MS-a dokazano je stanje stresa tretiranih mikroorganizama nakon jednostrukog tretmana, revitalizacije stanica te trostrukog tretmana istog uzorka. TEM analizom nakon tretmana dokazane su stanice s dezintegriranom membranom. Redukcija biofilma dokazana je nakon oba tretmana, plinskom plazmom i tekućinskom plazmom u mjehurićima.

Abstract (english)

The aim of this study was to investigate the influence of gas phase and liquid phase plasma discharges in bubbles on inactivation of 7 various microorganisms in stationary and exponentially growth phase (Escherichia coli MG1655-K12, Salmonella enterica serotype Typhimurium LT21, Listeria innocua ATCC 33091, Staphylococcus aureus 3048, Bacillus cereus 30, Rhodotorula spp 74 and Saccharomyces cerevisiae ATCC 204508). Furthermore, physico-chemical parameters, revitalization of samples after the treatment, leakage of cellular macromolecules, stress response and biofilm formation were analyzed. An experimental design with three different variables (frequency: 60, 90, 120 Hz, time: 5' and 10', gas: air and argon) was designed to determine optimal treatment conditions using two types of reactor at positive polarity and conductivity of media 100 μS cm-1. Complete inactivation in the stationary growth phase in both type of reactors and for all microorganisms was achieved, except for the Rhodotorula spp. In the exponential growth phase, complete inactivation by treatment of liquid plasma in argon bubbles was achieved for 4 microorganisms: S. enterica, L. innocua, S. aureus and S. cerevisiae. Although results of cellular leakage showed DNA and protein leakage, cell revitalization analysis proved the cell recovery. The most effective treatment, plasma discharges in bubbles (90 Hz, 10', argon) was selected for protein analyses of certain microorganisms in stationary growth phase: E. coli, L. innocua and S. cerevisiae. Under the same conditions selected microorganisms were analyzed with transmission electron microscopy (TEM). Proteomic analyses conducted by MALDI-TOF/TOF MS proved stress response after the single treatment, revitalization and triple treatment of the same sample. TEM analyses after the treatment illustrated cells with disintegrated membrane. Reduction in biofilm formation has been confirmed for both types of the reactor.

• Keywords: hladna plazma; mikroorganizmi; inaktivacija; revitalizacija; biofilm; odgovor na stres; fizikalno-kemijska svojstva
• Keywords (english): cold plasma; microorganisms; inactivation; revitalization; biofilm; response to stress; physico-chemical parameters
• Language: croatian
• URN:NBN: urn:nbn:hr:159:106047
• Promotion: 2018-12-12
• Study programme: Title: Postgraduate PhD Study in Food Technology; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti, područje biotehničkih znanosti, polje prehrambena tehnologija (doktor/doktorica znanosti, područje biotehničkih znanosti, polje prehrambena tehnologija)
• Type of resource: Text
• Extent: 184 str. : 30 cm
• File origin: Born digital
• Access conditions: Open access
• Created on: 2020-02-26 11:54:36