Belo, Isabel

Mota, M.

Pinheiro, Rita

Universidade do Minho: RepositoriUM

2nd European Symposium on Biochemical Engineering Science Porto, 16-19 September 1998 Bioprocesses for Food Production Posters  291 Study of Oxygen Effects on Thermus sp. RQ-1   M. Mota, I. Belo, R. Pinheiro Department of Biological Engineering, University of Minho (mmota@deb.uminho.pt)   Keywords: Thermophilic bacteria, oxygen transfer, pressure   Thermophilic microorganisms have potential applications in industry due to high cell growth and enzymatic reaction rates, lower costs in cooling systems, lower susceptibility to contamination, etc [1]. Cultivation of thermophiles can be used in bioconversions, as well as to obtain important thermostable enzymes [2]. Oxygen could be a limiting factor in aerobic thermophilic cultures because of its low solubility in the medium at high temperatures. In this work, oxygen demand of a culture of a Thermus bacteria (strain RQ-1) isolated from shallow hot springs on S. Miguel, Azores [3] was investigated in a batch fermenter at atmospheric pressure and 70 oC. Oxygen transfer capacity of the system was determinated by measuring the volumetric oxygen transfer coefficient (kLa). In the initial conditions of operation (200 rpm e 1 vvm) dissolved oxygen was completely exhausted from the medium at the exponential growth phase due the considerably high oxygen up-take rate of the cells. To eliminate oxygen limitation a 2-fold increase on stirring rate was applied. In order to study the possibility of using increased air pressure to increase oxygen solubility and consequently improve oxygen transfer rate to the medium, a pressurised reactor was used to cultivate Thermus RQ-1 cells. It was observed that air total pressure up to 5.6 atm (567.3 KPa) did not inhibited cell growth; on the contrary, cell concentration increased with pressure up to the maximum value used. Oxygen partial pressure increased by the reactor pressurisation also inducted the activity of the antioxidant enzymes superoxide dismutase (SOD) and catalase, mainly at the exponential growth phase. These enzymes have potential applications on food and pharmaceutical industries.   [1] Krahe, M., Antranikian, G., Märkl, H, FEMS Microbiology Reviews, 18, 271-285, 1996. [2] Hjörleifsdottir, S., Ritterbusch, W., Petursdottir, S. K. and Kristjansson, J. K., Biotechnol. Letters, 19, 147-150, 1997. [3] Manaia, C. M. and da Costa, M. S., J. Gen. Microbiol., 137, 2643-2648, 1991. 

Study of oxygen effects on Thermus sp. RQ-1

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Study of oxygen effects on Thermus sp. RQ-1

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