Xylitol production from D-xylose in a membrane bioreactor

Economical feasibility of xylitol production by microorganisms depends directly on the efficiency of conversion and productivity. A potential alternative to ensure this objective is continuous bioconversion. Xylitol production and separation methodology by a biotechnological route using the benefits of membrane technology were investigated. Xylitol produced by a strain of Candida guilliermondii was obtained using a synthetic medium containing D-xylose in a continuous membrane bioreactor. Moreover, hollow-fiber membranes were prepared and modules suitable for continuous fermentation medium sterilization were designed. The membrane that presented the best performance had maximum pore diameter of 0.2 mum and permeability of 42.9 L/(m(2).h.bar) for a simulated medium. The best results obtained with this system for the continuous production of xylitol in a membrane bioreactor was attained with a dilution rate of 0.03 h(-1), providing an efficiency of D-xylose conversion of 86% and productivity values up to 1.14 g of xylitol/L.h.