Oxygen uptake rate in production of xylitol by Candida guilliermondii with different aeration rates and initial xylose concentrations |
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Authors: | Gimenes Maria Antonieta P Carlos Luiz Cláudio S Faria Luís F F Pereira Nei |
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Institution: | 1.Departamento de Engenharia Bioquímica, Escola de Química/CT, Universidade Federal do Rio de Janeiro, Ilha do Fund?o, CEP: 21949-900, Rio de Janeiro, RJ, Brazil ;2.Departamento de Engenharia Química, Faculdade de Engenharia Química, CEP: 12600-000, Lorena, SP, Brazil ; |
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Abstract: | 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 (γ
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 (γ
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. |
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Keywords: | Xylitol Candida guilliermondii xylose-fermenting yeasts oxygen uptake |
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