An overview of different approaches and bioreactors for xylitol production by fermentation

Due to the many beneficial characteristics and possibilities of industrial applications of xylitol, an adequate addressing of engineering strategies is fundamental, aiming profitable yield and productivity of fermentative processes at industrial scale. In the developing biotechnological route, the different kinds of bioreactors and operation modes must be considered and systematically evaluated, mainly taking into account the particularities of the bioprocess, e.g., control of aeration rate and the presence of microbial inhibitors in the medium. At bench and pilot scale, stirred tank reactors have been reported for xylitol production using yeasts; however, other alternatives as bubble columns and fluidized bed reactors were also evaluated. Additionally, regarding bioreactor operation modes, batch, fed-batch, and continuous processes have been studied, presenting each one their specific advantages and concerns. Commonly, xylitol batch fermentation allows the study of process variables with profit-making control of operational conditions, while fed-batch and continuous processes are interesting alternatives to enhance process productivity. In this chapter, the main bioreactors and operation modes reported for xylitol production are discussed, including authors' investigations presenting specific approaches. The focus was a review exploring an overview of different approaches for fermentative methods for xylitol production, besides current techniques, e.g., applied to metabolic engineering, also discussing advancements and future perspectives.