Xylitol and ethanol co-production from sugarcane bagasse and straw hemicellulosic hydrolysate supplemented with molasses

Abstract

Co-production systems are a strategy used to diversify production chains and to enable more profitable processes. In addition, the valorization of the sugar-and-alcohol industry through by-product conversion into value-added products is environmentally friendly and enhances their competitiveness to other products available in the market. Thus, the aim of the current study is to evaluate xylitol and ethanol co-production by Candida tropicalis deriving from sugarcane by-products, such as bagasse and straw, supplemented with molasses. Sugarcane bagasse and straw hemicellulosic hydrolysate was obtained through dilute-acid hydrolysis with H2SO4; next, it was concentrated and detoxified with activated charcoal. Different commercial sucrose concentrations (5, 25 and 50 gL−1) were added to the bagasse and straw hemicellulosic hydrolysate in semi-defined medium. In addition, hydrolysate supplementation with sugarcane molasses was evaluated based on sucrose content (10 and 50 gL−1) adjustment. Batch fermentations were carried out in 125-mL Erlenmeyer flasks filled with 50 mL of medium, at 30 °C, 200 rpm, pH 5.5, for 48 h. Molasses supplementation adjusted to 50 gL−1 sucrose in sugarcane bagasse and straw hemicellulosic hydrolysate recorded the maximum xylitol (30.61 gL−1) and ethanol (47.97 gL−1) concentrations observed in the current study. Besides, volumetric xylitol (0.64 gL−1h−1) and ethanol (1.00 gL−1h−1) productivity was observed under the very same condition. Results have shown the likelihood of co-producing xylitol and ethanol through C. tropicalis by using sugarcane by-products to compose the fermentation medium as strategy to intensify and integrate these bioprocesses in sugarcane biorefineries.