Bioconversion of Birch Wood Hemicellulose Hydrolyzate to Xylitol

Abstract

A sugar solution containing 42.9 g l(-1) of xylose was prepared from the wood of Japanese white birch (Betula platyphylla var. japonica) by hydrolysis with 3 % sulfuric acid with a liquor-to-solid ratio of 4 (g g(-1)) at 120 °C for 1 h. During the acid hydrolysis, undesirable by-products were generated, such as acetic acid, furfural, and low-molecular-weight phenols, which inhibit bioconversion of xylose to xylitol. These inhibitors were successfully removed from the hydrolyzate by sorption onto a steam-activated charcoal followed by treatment with an anion exchange resin. Bioconversion of the detoxified hydrolyzate to xylitol by the yeast Candida magnoliae was investigated under the microaerobic conditions. The oxygen transfer rate (OTR) varied from 9.6 to 22.3 mmol O2 l(-1) h(-1). The best fermentative performance of C. magnoliae in the birch wood hydrolyzate (xylitol yield 0.74 g xylitol g xylose(-1); volumetric productivity 1.0 g l(-1) h(-1)) was obtained at the OTR of 12.6 mmol O2 l(-1) h(-1).

Optimization of Salts Supplementation on Xylitol Production by Debaryomyces hansenii Using a Synthetic Medium or Corncob Hemicellulosic Hydrolyzates and Further Scaled Up

“…The previous results showed the positive effect of supplementing the culture medium based on d -xylose as the carbon source with salts. However, nowadays the use of commercial d -xylose for the biological production of xylitol is being replaced by the use of xylose-containing media obtained from a great diversity of lignocellulosic biomass such as birch wood, sorghum forage biomass, corncobs, − or olive stones . These subproducts have been investigated with the objective to reduce the production costs and minimize their environmental impact.…”

“…Culture media were formulated with hydrolyzates obtained after hydrolysis with sulfuric acid, neutralization with calcium carbonate, and final detoxification with charcoal. Adsorption with activated charcoal has been widely assayed to remove mainly phenolic compounds in hemicellulosic hydrolyzates. ,,, Detoxified liquors recovered by filtration showed the following composition: 1.6 ± 0.31 g/L glucose; 29.3 ± 5.85 g/L xylose; 3.0 ± 0.61 g/L arabinose; 0.71 ± 0.14 g/L lactic acid; 0.12 ± 0.023 g/L glycerol; 4.4 ± 0.88 g/L acetic acid; 1.55 ± 0.31 g/L oxalic acid; 0.8 ± 0.16 g/L citric acid; 0.23 ± 0.046 g/L tartaric acid, and <0.1 g/L malic acid.…”

Directed evolution and secretory expression of xylose isomerase for improved utilisation of xylose in Saccharomyces cerevisiae

“…Most early studies on the utilisation of lignocellulosic biomass have focused on the fermentation of glucose derived from cellulose, which can be easily converted to ethanol. As lignocellulosic biomass contains a significant amount of hemicellulose (up to 25–50% of the total dry weight), there is a need to develop a cost-effective bioethanol production process that efficiently utilises xylose, which is the most abundant pentose sugar in hemicellulose [ 2 , 3 ].…”

Xylitol Separation from a Polyol Mixture Using Lanthanide Ion-loaded Resins

“…Among them, xylitol is a highvalue chemical due to its use as a sweetener. [10][11][12][13][14] However, a small amount of glycerol (b.p. : 290 °C) interferes with the crystallization of xylitol because of its highly hygroscopic nature.…”