Valorization of the sugarcane bagasse and straw hemicellulosic hydrolysate through xylitol bioproduction: effect of oxygen availability and sucrose supplementation as key factors

Abstract

Sugarcane agroindustry, one of the most important in Brazilian economy, can diversify its product portfolio in a biorefinery context through the use of by-products as feedstocks to produce bioenergy and high-added value chemicals, such as xylitol, which is a sweetener with applications in the food and pharmaceutical industries and with a growing market. Opportunities for the integration of xylitol bioproduction in a sugarcane biorefinery can be based on the valorization of bagasse, straw, and molasses, which are feedstocks with high content of carbohydrates, specifically xylose from the hemicellulosic fraction of the lignocellulosic biomasses, and sucrose from molasses that can act as co-substrate on this bioprocess. Xylitol bioproduction from the hemicellulosic hydrolysate of the sugarcane bagasse and straw mixture was herein investigated. Particularly, the effects of sucrose supplementation to the medium on the fermentative performance of Candida tropicalis depending on its initial concentration and oxygen availability (expressed as KLa), which is one of the most important factors for this bioprocess, are discussed. Xylitol yield (0.86 gg−1) and volumetric productivity (0.51 gL−1 h−1) were concomitantly maximized by using sucrose (0.91 gL−1) and KLa (6.5 h−1) within the optimization range. Furthermore, the addition of sugarcane molasses to the hemicellulosic hydrolysate improved xylitol production, in comparison with the conventional supplementation. Scientific background is given to contribute to supporting the potential integration of xylitol bioproduction to a sugarcane biorefinery, which may enhance both the feasibility of this bioprocess and sugarcane agroindustry valorization based on the applications and growing xylitol market.