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| Author(s): |
Ana Luiza Fanchini Messas
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia de Alimentos |
| Defense date: | 2011-07-28 |
| Examining board members: |
Gabriela Alves Macedo;
Helia Harumi Sato;
Vânia Battestin Wiendl
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| Advisor: | Gabriela Alves Macedo |
| Abstract | |
Phytic acid is the main source of phosphorus storage in cereals and legumes, and its salt is known as phytate. Phytate is not digested by the gastrointestinal tract of monogastric animals and, in food for human consumption, phytate is considered an antinutritional factor because of its ability in chelating various metals and binding to proteins, thereby reducing the bioavailability of proteins and nutritionally important minerals as zinc, iron, calcium, and others. One of the most effective strategies for reducing phytate content in animal feed and food for human consumption has been the use of exogenous enzymes that degrade phytate, the phytases. Thus, during the last 20 years, the studies to discover new sources of this enzyme have been intensified. Phytase is widely distributed in nature, being found in animals, plants and microorganisms. The enzyme present in plants is less resistant to heat treatment and is less stable under physiological conditions of the gastrointestinal tract, since the microorganisms can withstand high temperatures, depending on the strain. In this study, it was made the production, the optimization of the medium of culture and growing conditions and characterization of phytase produced by the bacteria Burkholderia sp. It was defined as the culture medium optimized for the production of phytase of Burkholderia sp. in shaken flasks, in 72 hours of fermentation: sodium phytate 0.075%, sucrose 0.16%, bacteriological peptone 0.2%, MgSO4.7H2O 0.05%, KCl 0.05%, FeSO4.7H2O 0.0001%, MnSO4.H2O 0.00075% e CaCl2 0.01%. It was possible to increase the production of phytase in 110% (1.01 U/mL to 2.12 U/mL). The growing conditions (rotation and temperature) optimized for production of phytase in shaken flasks were 250 rpm and 37°C, after 48 hours of fermentation in shaker. In biochemical characterization, phytase showed pH optimum at 5.5 and estability in the pH range of 3 to 7, after 1 hour of incubation at 50°C. Phytase showed optimum temperature at 60°C and remained stable after 1 hour of treatment at temperatures between 25°C and 50°C, showing 40% of reduction of the activity after 1 hour of treatment at 60°C. In the study of the effect of ions, using the concentration of 10 mM for the salts tested, the most importants results were the increase of the activity of phytase in 41% with the addition of Ba2+ and the decrease of the activity of phytase in 98% and 96%, respectively, with the addition of Fe2+ and Zn2+, almost completely inhibiting the enzyme. For the concentration of 1 mM of the salts, the addition of Mn2+, Fe2+, Cu2+, Zn2+ and Fe3+ caused significant reductions in activity of phytase, in 61%, 45%, 45%, 31% and 30%, respectively. Phytase produced by Burkholderia sp. presented values of Km and Vmax of 0.02 mM e 6.20 'mol Pi/min/mg, respectively (AU) | |