Aspects of xylitol formation in sugarcane bagasse hydrolysate by Candida guilliermondii in the presence of tetracycline

The bioconversion of xylose into xylitol using pH values of 4.0, 5.5, and 7.0 and tetracycline concentrations of 20 and 40 mg/L was carried out to verify the influence of these parameters on Candida guilliermondii metabolism for xylitol production. Experiments were performed with sugarcane bagasse hemicellulosic hydrolysate (48.5 g/L of xylose) in 125-mL Erlenmeyer flasks, at 30 degrees C, 200 rpm, during 88 h. The results demonstrated that the bioconversion of xylose into xylitol was significantly influenced by the pH. On the other hand, in media containing 20 or 40 mg/L of tetracycline, this bioconversion was not significantly affected. The best results of xylitol production were obtained in hemicellulosic hydrolysate without tetracycline, at pH 7.0. In these conditions, the maximum specific growth rate was 0.014/h and the yield factor of xylitol and volumetric productivity were 0.85 g/g and 0.70 g/L/h respectively. Xylitol and cell growth occurred simultaneously.