Acid Hydrolysis Of Sugarcane Bagasse Research Articles

Optimization of Acid Hydrolysis of Sugarcane Bagasse and Investigations on its Fermentability for the Production of Xylitol by <I>Candida guilliermondii

The dilute-acid hydrolysis of sugarcane bagasse was optimized using a statistical experimental design resulting in hydrolysates containing 57.25 g/L of xylose, which were fermented with a high inoculum concentration (10 g/L of the yeast Candida guilliermondii IM/UFRJ 50088). The addition of urea reduced the time of conversion (tC) to 75 h (without nitrogen source addition tC > 127 h), and, consequently, improving the rates of xylitol bioproduction. Fermentator experiments, using the optimized conditions, resulted in enhanced conversion rates, reducing tC to 30 h. The stability of the yeast in the hydrolysate was also verified in a 480-h cultivation.

Xylitol production via catalytic hydrogenation of sugarcane bagasse dissolving pulp liquid effluents over Ru/C catalyst

AbstractXylose‐rich liquid effluents generated by the acid hydrolysis of sugarcane bagasse for production of dissolving pulp were converted to xylitol, a highly valued chemical specialty, via catalytic hydrogenation over Ru/C. From the eco‐efficiency standpoint, this initiative emerges as an attractive way to promote a chemical valorisation of bagasse dissolving pulp wastewaters. Copyright © 2004 Society of Chemical Industry

Effect of acetic acid present in bagasse hydrolysate on the activities of xylose reductase and xylitol dehydrogenase in Candida guilliermondii.

The first two steps in xylose metabolism are catalyzed by NAD(P)H-dependent xylose reductase (XR) (EC 1.1.1.21) and NAD(P)-dependent xylitol dehydrogenase (XDH) (EC 1.1.1.9), which lead to xylose-->xylitol-->xylulose conversion. Xylitol has high commercial value, due to its sweetening and anticariogenic properties, as well as several clinical applications. The acid hydrolysis of sugarcane bagasse allows the separation of a xylose-rich hemicellulosic fraction that can be used as a substrate for Candida guilliermondii to produce xylitol. However, the hydrolysate contains acetic acid, an inhibitor of microbial metabolism. In this study, the effect of acetic acid on the activities of XR and XDH and on xylitol formation by C. guilliermondii were studied. For this purpose, fermentations were carried out in bagasse hydrolysate and in synthetic medium. The activities of XR and XDH were higher in the medium containing acetic acid than in control medium. Moreover, none of the fermentative parameters were significantly altered during cell culture. It was concluded that acetic acid does not interfere with xylitol formation since the increase in XR activity is proportional to XDH activity, leading to a greater production of xylitol and its subsequent conversion to xylulose.