Određivanje parametara stresa u bakterije Listeria inoccua nakon tretmana ultrazvukom

master's thesis

• Title (english): Determination of stress parameters in bacteria Listeria innocua after ultrasound treatment
• Author: Josipa Zovko
• 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: 2017, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Food Technology

Abstract

Listeria innocua nepatogena je bakterija, široko rasprostranjena u okolišu i hrani, te se zbog sličnosti s patogenom bakterijom Listeria monocytogenes koristi kao modelni organizam u istraživanjima. U ovom radu određivani su mehanički utjecaji ultrazvuka visoke snage na stvaranje parametara stresa bakterijske kulture Listeria innocua ATC33090. Uzorci bakterijske suspenzije tretirani su toplinom te toplinom i ultrazvukom u kombinaciji. Uzorcima koji su tretirani ultrazvučnom sondom frekvencije 20 kHz, mjerene su tri nezavisne varijable: amplituda (75 %, 100 %), temperatura (40 °C, 60 °C) i vrijeme tretmana (5, 10 minuta). Rezultati su analizirani metodom odzivne površine (RSM) koristeći program STATGRAPHICS Centurion. Pri 40 °C i amplitudi od 100 %, postignuta je potpuna inaktivacija već nakon 5 minuta ultrazvučnog tretmana, te najviši stupanj redukcije (4,31 log10 CFU ml-1). Najveći porast koncentracije slobodnih radikala je 30 % od početne vrijednosti, pri 60 °C i 100 %-tnoj amplitudi, nakon 10 minuta tretmana. Kod istih uvjeta tretmana u vremenu od 5 minuta dobivena je najznačajnija redukcija stvaranja biofilma (92,25 %). Primjenom viših temperatura (60 °C) uz ultrazvučno tretiranje dolazi do apoptoze stanica te se one ne mogu revitalizirati. Značajnu ulogu pri inaktivaciji bakterijskih stanica osim uvjeta tretmana ima i kavitacijski efekt ultrazvuka, pri kojem se formiraju slobodni radikali.

Abstract (english)

Listeria innocua is a non-pathogenic bacterium, widespread in the environment and food, and because of its similarity to the pathogenic bacterium Listeria monocytogenes, is used as a model organism in researches. In this paper, the mechanical effects of the high power ultrasound have been determined on the creation of stress parameters of bacterial culture Listeria innocua ATC33090. Samples of the bacterial suspension were treated by heat and ultrasound in combination. Samples were analyzed by ultrasound probe frequency of 20 kHz and three independent variables were measured: amplitude (75 %, 100 %), temperature (40 °C, 60 °C) and treatment time (5, 10 minutes). The results were analyzed by response surface methodology (RSM) using the STATGRAPHICS Centurion program. At 40 °C and 100 % amplitudes, complete inactivation was achieved after 5 minutes of ultrasonic treatment and the highest degree of reduction (4,31 log10CFU ml-1). The highest increase in free radical concentration was 30 %, at 60 °C and 100 % amplitude, after 10 minutes of treatment. At the same treatment conditions, in 5 minutes the most significant reduction in biofilm production (92.25 %) was achieved. Applied to higher temperatures (60 °C) with ultrasound treatment, cell apoptosis occurs and cells can not be revitalized. A significant role in the inactivation of bacterial cells, apart from the condition of the treatment, has the cavitation effect of ultrasound, creating free radicals.

• Keywords: ultrazvuk; Listeria innocua; kavitacija; biofilm; slobodni radikali; stupanj redukcije; stanično istjecanje; revitalizacija stanica
• Keywords (english): ultrasound; Listeria innocua; cavitation; biofilm; free radicals; degree of reduction; cellular leakage; cell revitalization
• Language: croatian
• URN:NBN: urn:nbn:hr:159:772335
• 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: 2017-11-13 14:35:19