Overcoming extended lag phase on optically pure lactic acid production from pretreated softwood solids.

Optically pure lactic acid (LA) is needed in PLA (poly-lactic acid) production to build a crystalline structure with a higher melting point of the biopolymer than that of the racemic mixture. Lignocellulosic biomass can be used as raw material for LA production, in a non-food biorefinery concept. In the present study, genetically engineered ZP26 was cultivated in a simultaneous saccharification and fermentation (SSF) process using steam pretreated softwood solids as a carbon source to produce optically pure D-LA.

Mass Transport of Lignin in Confined Pores.

A crucial step in the chemical delignification of wood is the transport of lignin fragments into free liquor; this step is believed to be the rate-limiting step. This study has investigated the diffusion of kraft lignin molecules through model cellulose membranes of various pore sizes (1-200 nm) by diffusion cells, where the lignin molecules diffuse from donor to acceptor cells through a membrane, where diffusion rate increases by pore size. UV-vis spectra of the donor solutions showed greater absorbance at higher wavelengths (~450 nm), which was probably induced by scattering due to presence of large molecules/clusters, while acceptor samples passed through small pore membranes did not.

Rational and evolutionary engineering of Saccharomyces cerevisiae for production of dicarboxylic acids from lignocellulosic biomass and exploring genetic mechanisms of the yeast tolerance to the biomass hydrolysate.

Background: Lignosulfonates are significant wood chemicals with a $700 million market, produced by sulfite pulping of wood. During the pulping process, spent sulfite liquor (SSL) is generated, which in addition to lignosulfonates contains hemicellulose-derived sugars-in case of hardwoods primarily the pentose sugar xylose. The pentoses are currently underutilized.

Identification of modifications procuring growth on xylose in recombinant Saccharomyces cerevisiae strains carrying the Weimberg pathway.

The most prevalent xylose-assimilating pathways in recombinant Saccharomyces cerevisiae, i.e. the xylose isomerase (XI) and the xylose reductase/xylitol dehydrogenase (XR/XDH) pathways, channel the carbon flux through the pentose phosphate pathway and further into glycolysis.

Exploring D-xylose oxidation in Saccharomyces cerevisiae through the Weimberg pathway.

Engineering of the yeast Saccharomyces cerevisiae towards efficient D-xylose assimilation has been a major focus over the last decades since D-xylose is the second most abundant sugar in nature, and its conversion into products could significantly improve process economy in biomass-based processes. Up to now, two different metabolic routes have been introduced via genetic engineering, consisting of either the isomerization or the oxido-reduction of D-xylose to D-xylulose that is further connected to the pentose phosphate pathway and glycolysis. In the present study, cytosolic D-xylose oxidation was investigated instead, through the introduction of the Weimberg pathway from Caulobacter crescentus in S.

A rapid method for analysis of fermentatively produced D-xylonate using ultra-high performance liquid chromatography and evaporative light scattering detection.

An ultra-high performance liquid chromatography (UHPLC) based method for the analysis of d-xylonate was developed using an amide column in combination with an evaporative light scattering (ELS) detector. Separation of d-xylonate from other components of the fermentation medium was achieved. The dynamic range of the method was 0.

Succinic acid production by Actinobacillus succinogenes from batch fermentation of mixed sugars.

Succinic acid production from the monosaccharides xylose, arabinose, glucose, mannose and galactose was studied using the bacterium Actinobacillus succinogenes. In Duran bottle cultures, containing 10 g/L of each of sugar, succinic acid was produced from all sugars except for galactose. The highest succinate yield, 0.

Saccharomyces cerevisiae: a potential host for carboxylic acid production from lignocellulosic feedstock?

Carboxylic acids are important bulk chemicals that can be used as building blocks for the production of polymers, as acidulants, preservatives and flavour compound or as precursors for the synthesis of pharmaceuticals. Today, their production mainly takes place through catalytic processing of petroleum-based precursors. An appealing alternative would be to produce these compounds from renewable resources, using tailor-made microorganisms.