Oxygen Uptake Rate in Production of Xylitol by Candida guilliermondii with Different Aeration Rates and Initial Xylose Concentrations
The global oxygen uptake rate (OUR) and specific oxygen uptake rates (SOUR) were determined for different values of the volumetric oxygen mass transfer coefficient (15,43, and 108 h–1), and for varying initial xylose concentrations (50, 100, 150, and 200 g/L) in shaking flasks. The initial cell concentration was 4.0 g/L, and there was only significant growth in the fermentation with the highest oxygen availability. In this condition, OUR increased proportionally to cell growth, reaching maximum values from 2.1 to 2.5 g of O2/(L·h) in the stationary phase when the initial substrate concentration was raised from 50 to 200 g/L, respectively. SOUR showed different behavior, growing to a maximum value coinciding with the beginning of the exponential growth phase, after which point it decreased. The maximum SOUR values varied from 265 to 370 mg of O2/(g of cell·h), indicating the interdependence of this parameter and the substrate concentration. Although the volumetric productivity dropped slightly from 1.55 to 1.18 g of xylitol/(L·h), the strain producing capacity (ϒ P/X ) rose from 9 to 20.6 g/g when the initial substrate concentration was increased from 50 to 200 g/L. As for the xylitol yield over xylose consumed (ϒ P/S ), there was no significant variation, resulting in a mean value of 0.76 g/g. The results are of interest in establishing a strategy for controlling the dynamic oxygen supply to maximize volumetric productivity.
Index EntriesXylitol Candida guilliermondii xylose-fermenting yeasts oxygen uptake
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- 5.van Dijken, J. P. and Scheffers, W. A. (1986), FEMS Microbiol. Rev. 32, 199–224.Google Scholar
- 6.Alves, L. A., Vitolo, M., Felipe, M. G. A., Almeida e Silva, J. B. (2000), Anais do XIII Simpósio National de Fermentações, Rio de Janeiro (CD-ROM).Google Scholar
- 8.du Preez, J. C. and van der Walt, J. P. (1983), Biotechnol. Lett. 6, 395–400.Google Scholar
- 9.Sá, M. C. A. (1993), MSc thesis, Post Graduate Program in Chemical and Biochemical Processes Technology, School of Chemistry, UFRJ, Rio de Janeiro, Brazil.Google Scholar
- 10.Ururahy, A. (1998), DSc thesis, Post Graduate Program in Chemical and Biochemical Processes Technology, School of Chemistry, UFRJ, Rio de Janeiro, Brazil.Google Scholar
- 11.Bailey, J. E. and Ollis, D. F. (1986), Biochemical Engineering Fundamentals, 2nd ed., McGraw-Hill, NY.Google Scholar
- 12.Stryer, L. (1995), Biochemistry, 4th ed., W. H. Freeman, NY.Google Scholar
- 14.Timasheff, S. N., Yoshiro, K., Tsutomu, A., and Tiao-Yin, L. (1994), Biochemistry 33, 15,178–15,189.Google Scholar
- 15.Aguiar, W. B. Jr. (1999), MSc thesis, Post Graduate Program in Chemical and Biochemical Processes Technology, School of Chemistry, UFRJ, Rio de Janeiro, Brazil.Google Scholar