Repeated Batch Cell-Immobilized System for the Biotechnological Production of Xylitol as a Renewable Green Sweetener

Abstract

The present paper studies the biotechnological production of xylitol using sugarcane bagasse hydrolysate in a repeated batch fermentation system with immobilized cells of Candida guilliermondii FTI20037. Immobilized cell system is considered as an attractive alternative to reuse the well-grown and adapted yeast cells in a new fresh fermentation media, without the need of the inoculum stage. In this work, seven repeated batches were performed in a fluidized bed bioreactor using immobilized cells in calcium alginate beads. According to the obtained results it was observed that the immobilized cells of C. guilliermondii can be reused for six successive batches maintaining an average xylitol yield (Y(p/s)) of 0.7 g/L and a volumetric productivity (Q(p)) of 0.42 g/Lh at the end of 432 h of fermentation. On the other hand, in the seventh batch (504 h), a decrease of 44 % in the final concentration of xylitol was observed. This reduction can be explained by the possible diffusion and accumulation of insoluble substances, found in the hemicellulosic hydrolysate, in the interior of the immobilization support resulting in substrate mass transfer limitations.