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| Author(s): |
Roberta Regina Delboni
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Instituto de Matemática, Estatística e Computação Científica |
| Defense date: | 2009-02-03 |
| Examining board members: |
Hyun Mo Yang;
Izildinha Moreno;
Marco Antonio Teixeira
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| Advisor: | Hyun Mo Yang |
| Abstract | |
A major challenge for the food industry is the attending of demands of consumers for minimally processed foods, which do not contain chemical preservatives neither were submitted to intensive heat treatments, but at the same time ensuring microbiological safety of these products. To study quantitatively the biological control as a technique of conservation, we developed a mathematical model to describe the interaction between lactic acid bacteria and the pathogen Listeria monocytogenes in the food. The steady states and dynamical trajectories analyses of the model allowed us to study the possible action of the lactic acid and the bacteriocin, produced by lactic acid bacteria, in the reduction of activity of Listeria in the food. Through the knowledge of the bacteriocin biosynthesis biochemical regulation, we developed other model focusing on the production of bacteriocin nisin. We then have shown the effect of nisin on the response of the system which regulates the expression of genes required for biosynthesis. This model was extended to include synthesis of nisin in order to study the dynamic of the regulatory system in a growing bacterial population. Both models demonstrate a typical behavior of hysteresis. Using the last model, we have shown the cell-density-dependent regulation of bacteriocin production, called mechanism of quorum sensing, which is the switch between two stable steady solutions corresponding to non-activated and activated states of the regulatory system (AU) | |