Xylitol Bioproduction in Hemicellulosic Hydrolysate Obtained from Sorghum Forage Biomass

Abstract

This study evaluated the biotechnological production of xylitol from sorghum forage biomass. The yeast Candida guilliermondii was cultivated in hemicellulosic hydrolysates obtained from biomass of three sorghum varieties (A, B, and C). First, the biomass was chemically characterized and subjected to dilute acid hydrolysis to obtain the hemicellulosic hydrolysates which were vacuum-concentrated and detoxified with activated charcoal. The hemicellulosic hydrolysates (initial pH 5.5) were supplemented with nutrients, and fermentations were conducted in 125-mL Erlenmeyer flasks containing 50 mL medium, under 200 rpm, at 30 °C for 96 h. Fermentations were evaluated by determining the parameters xylitol yield (Y P/S ) and productivity (QP), as well as the activities of the enzymes xylose reductase (XR) and xylitol dehydrogenase (XDH). There was no significant difference among the three varieties with respect to the contents of cellulose, hemicellulose, and lignin, although differences were found in the hydrolysate fermentability. Maximum xylitol yield and productivity values for variety A were 0.35 g/g and 0.16 g/L.h(-1), respectively. It was coincident with XR (0.25 U/mg prot) and XDH (0.17 U/mg prot) maximum activities. Lower values were obtained for varieties B and C, which were 0.25 and 0.17 g/g for yield and 0.12 and 0.063 g/L.h(-1) for productivity.

Xylose-Enriched Ethanol Fermentation Stillage from Sweet Sorghum for Xylitol and Astaxanthin Production

“…Similar xylitol yields at this level have been reported for C. mogii when cultivated on hydrolysate obtained from big bluestem grass [33] and corn stover hydrolysate after detoxification [34]. Other xylitol fermentation research utilizing Candida guilliermondii cultivated on hemicellulosic hydrolysates from forage sorghum generated a xylitol yield around 0.35 g xylitol/g xylose consumed which also compares well with the yield calculated from Figure 4 [35]. Using C. guilliermondii on sorghum straw hydrolysate produced a yield of 0.44 g xylitol/g xylose consumed, which slightly outperforms the yield obtained here [36].…”

Stable isotope (δ13C) profiling of xylitol and sugar in South Africa

“…16,22 On an industrial scale, xylitol is currently produced by chemical reduction of xylose (D-xylose), traditionally derived from the bark of birch trees (Betula pendula) and other hardwoods. 4,23,24 More recently, corncobs (Zea mays) 25 , sugarcane bagasse, and wheat, sorghum and rice straw [26][27][28] have been used as sources of xylose; in China, xylitol production from corncob reached 50 000 tons in 2008 25,29 . Production from corncob is favoured as it is less expensive than production from birch.…”

Dilute Acid Hydrolysis of Sweet Sorghum Bagasse and Fermentability of the Hemicellulosic Hydrolysate

“…The response surface plot for xylose, similar to that observed for glucose, shows that the acid concentration and temperature were the variables that most favored the hydrolysis of hemicellulose to xylose. The best xylose yields were obtained using an acid concentration of 1.75% and hydrolysis temperature of 121 o C. Camargo et al (2015) described similar levels of xylose in the forage sorghum bagasse hemicellulosic hydrolysate (16.76 -17.42 g/L) when hydrolysis was carried out with 2% sulfuric acid at 121 o C for 70 minutes. With sorghum straw, Sene et al (2011) obtained higher concentrations of xylose (17.69 g/L) and less glucose (2.1 g/L) and arabinose (1.81 g/L) than those found in the present work.…”