title: Biotechnological production of xylitol: enhancement of monosaccharide production by post-hydrolysis of dilute acid sugarcane hydrolysate.
abstract: Dilute-acid hydrolysis pretreatment of sugarcane bagasse resulted in release of 48% (18.4 g/L) of the xylan in the hemicellulose fraction into the hydrolysate as monomeric xylose. In order to enhance the recuperation of this monomer, a post-hydrolysis stage consisted of thermal treatment was carried out. This treatment resulted in an increase in xylose release of 62% (23.5 g/L) of the hemicellulose fraction. Original and post-hydrolysates were concentrated to the same levels of monomeric xylose in the fermentor feed. During the fermentation process, cellular growth was observed to be higher in the post-hydrolysate (3.5 g/L, Y(x/s) = 0.075 g cells/g xylose) than in the original hydrolysate (2.9 g/L, Y(x/s) = 0.068 g cells/g xylose). The post-treated hydrolysate required less concentration of sugars resulting in a lower concentration of fermentation inhibitors, which were formed primarily in the dilute acid hydrolysis step. Post-hydrolysis step led to a high xylose-xylitol conversion efficiency of 76% (0.7 g xylitol/g xylose) and volumetric productivity of 0.68 g xylitol/L h when compared to 71% (0.65 g xylitol/g xylose and productivity of 0.61 g xylitol/L h) for the original hemicellulosic hydrolysate.
authors.affiliation: Engineering School of Lorena-USP, Biotechnology Department, Campinho road, P.O. Box 116, CEP: 12.602-810, Lorena, SP, Brazil. bsarrouh@yahoo.es
authors.forename: Boutros Fouad
authors.initials: BF
authors.lastname: Sarrouh
authors.forename: Ricardo
authors.initials: R
authors.lastname: de Freitas Branco
authors.forename: Silvio Silvério
authors.initials: SS
authors.lastname: da Silva
mesh_terms: D001709:Biotechnology / Q000379:methods; D006868:Hydrolysis; D009005:Monosaccharides / Q000096:biosynthesis*; D031786:Saccharum / Q000378:metabolism*; D014993:Xylitol / Q000096:biosynthesis*
chemical_list: D009005:Monosaccharides; D014993:Xylitol