Glucose repression is one of the main limitations in mixed lignocellulosic sugar fermentation for cost-effective production of fuels and chemicals. Here we report a novel strategy to overcome glucose repression by co-expressing a cellobiose transporter and a β-glucosidase in an engineered d-xylose-utilizing Saccharomyces cerevisiae strain. The resulting strain can simultaneously utilize cellobi...

BACKGROUND There has been a great deal of interest in fuel productions from lignocellulosic biomass to minimize the conflict between food and fuel use. The bioconversion of xylose, which is the second most abundant sugar present after glucose in lignocellulosic biomass, is important for the development of cost effective bioprocesses to fuels. Rhodococcus opacus PD630, an oleaginous bacterium, a...

In this work, two fermentations at different temperatures (25 and 30oC), with cell recycling, were accomplished to produce ethanol, using a mix of commercial substrates, xylose (70%) and glucose (30%), as organic source for Scheffersomyces stipitis. Five consecutive fermentations of 80 g L (1o, 2o and 3o recycles), 96 g L (4o recycle) and 120 g L (5o recycle)reduced sugars led to a final maximu...

Hemicellulose consists primarily of pentose sugars, joined together in a polysaccharide chain with D-xylose as the most abundant component. Ileal digestibility and urinary excretion of D-xylose and associated effects of this pentose sugar on ileal and faecal digestibility of dry matter (DM), organic matter (OM), gross energy (GE) and nitrogen were studied in pigs. Castrated pigs were prepared w...

Glucose isomerase (GI) (D-xylose ketol-isomerase; EC. 5.3.1.5) catalyzes the reversible isomerization of D-glucose and D-xylose to D-fructose and D-xylulose, respectively. The enzyme has the largest market in the food industry because of its application in the production of high-fructose corn syrup (HFCS). HFCS, an equilibrium mixture of glucose and fructose, is 1.3 times sweeter than sucrose a...

BACKGROUND Baker's yeast (Saccharomyces cerevisiae) has been engineered for xylose utilization to enable production of fuel ethanol from lignocellulose raw material. One unresolved challenge is that S. cerevisiae lacks a dedicated transport system for pentose sugars, which means that xylose is transported by non-specific Hxt transporters with comparatively low transport rate and affinity for xy...

A cybernetic framework is presented which views microbial response in multiple substrate environments as a judicious investment of cellular resources in synthesizing different key proteins according to an optimal regulatory strategy. A mathematical model is developed within the cybernetic framework for the diauxic growth of Klebsiella pneumoniae on a mixture of D-glucose and D-xylose. The "bang...

The aim of this article is to illustrate practical issues that may arise when applying MCMC methods in a real case. MCMC methods are used over a model of mixture of distributions, in order to determine honnesty specifications about some kind of product. First, assuming a known number of components, parameters of each component are estimated using Gibbs sampling. Convergence and label-switching ...

Dehydration of the most relevant biomass derived monosaccharides, xylose, glucose and fructose, was investigated to attain value-added platform chemicals: furfural, hydroxymethylfurfural (5-HMF) levulinic acid (LA).