Effect of the cane bagasse hydrolysate detoxification on the phenols removal, sugars loss and xylose-to-xylitol bioconversion

Abstract

The hydrolysate resulting from the acid hydrolysis process, a method usually employed for different lignocellulosic materials, contains, besides sugars, compounds that are toxic to the microorganisms. Among them, there are the phenolic compounds, which have inhibitory effect on the xylose-to-xylitol bioconversion, due to their individual action, and also to their synergistic interaction with other compounds present in the hydrolysates, such as furfural, hydroxymethylfurfural and acetic acid. Furthermore, the phenolic compounds are responsible for the dark color of the hydrolysate, which interferes in the xilitol downstream process. This work evaluated two procedures of sugarcane bagasse hydrolysate detoxification: pH adjusting with active charcoal adsorption, and a vegetable-origin polymer flocculation technique. The total phenolics and the xylose and glycose concentrations were determined by Folin-Ciocalteu method and liquid chromatography, respectively. Both treatments resulted in reduction of total phenolics concentration. However, the use of active charcoal resulted in higher loss of this compound (88.5% removal), which represents 17.8% increase when comparised to the use of polymer. The xylose loss was minimum (8%) for both used treatments. The treatment using the combination of pH adjustment and active charcoal adsorption was more efficient than the procedure that used vegetable-origin polymer. Considering these preliminary assays and also the polymer low cost and its biodegradability, researches must be performed in order to establish conditions for the most effective use of this compound, improving the hydrolysate fermentability and decreasing the xylose loss.