45H-1 |
Culture medium optimization of Candida parapsilosis Y-2315 for xylitol production |
I. A. Santos-Sánchez, Depto. de Ciencia y tecnología de Alimentos, Universidad Autónoma de Tamaulipas, UAM Reynosa-Aztlán, Reynosa, Mexico, J. A. Ramírez, Dept. of Food Science & Technology, Univ. Autónoma de Tamaulipas, UAM Reynosa-Aztlán, Reynosa, Tamaulipas, 88700, Mexico, J. M. Cruz, Departamento de Ingeniería Química, Universidad de Vigo, Facultad de Ciencias, As Lagoas, Ourense, 32004, Spain, and M. VÁZQUEZ, Department of Analytical Chemistry - Area Food Technology, Universidad de Santiago de Compostela, Escuela Politécnica Superior, Lugo, 27002, Spain. Xylitol, a five-carbon polyol with high sweetening power, is tolerated by diabetic, has anticariogenic properties, has been recommended for parental nutrition and used as a food ingredient in sugar-free confections, yogurt, jams, bakery products and drinks. Xylitol can be obtained by various technologies, including: i) Extraction from some fruits an vegetable (this procedure is not economical owing to its small concentrations); ii) Chemical reduction of xylose (this process is relatively expensive because of the extensive purification and the separation steps required); iii) Biotechnological conversion of xylose solution (this is a selective and promising process for xylitol production). The bioconversion can be carried out with fungi, bacteria, yeast or purified enzyme from these microorganisms. The most studied xylitol producers are yeasts, being the strains of the genus Candida and Debaryomyces hansenii the best natural producers. This works deals with xylitol production by the yeast Candida parapsilosis Y-2315 in synthetic sugar solutions. An experimental design was made in order to optimize the composition of the media. The independent variables were yeast extract, malt extract and peptone in the range 0-6 g/L. Batch fermentations were performed with free cells in an orbital shaker at 125 rpm and 26ºC under microaerobic conditions, using 250 ml Erlenmeyer flasks with 100 ml of fermentation medium. The supplementation of the media with yeast extract, malt and peptone was optimized. By using a initial sugar concentration of 13 g of xylose/L, the model predict that 4.1 g xylitol/L can be obtained after 96 h by supplementation of the media with 5.65 g yeast extract/L, 6 g malt extract/L and 4.51 g peptone /L. The xylitol yield (0.314 g/g) and biomass yield (0.5 g/g) are in the range of other xylitol producers microorganisms.
Session 45H, International: General
|