Engineering nonphosphorylative metabolism to generate lignocellulose-derived products.

Conversion of lignocellulosic biomass into value-added products provides important environmental and economic benefits. Here we report the engineering of an unconventional metabolism for the production of tricarboxylic acid (TCA)-cycle derivatives from D-xylose, L-arabinose and D-galacturonate. We designed a growth-based selection platform to identify several gene clusters functional in Escherichia coli that can perform this nonphosphorylative assimilation of sugars into the TCA cycle in less than six steps.

Engineered biosynthesis of medium-chain esters in Escherichia coli.

Medium-chain esters such as isobutyl acetate (IBAc) and isoamyl acetate (IAAc) are high-volume solvents, flavors and fragrances. In this work, we engineered synthetic metabolic pathways in Escherichia coli for the total biosynthesis of IBAc and IAAc directly from glucose. Our pathways harnessed the power of natural amino acid biosynthesis.

Scalable production of mechanically tunable block polymers from sugar.

Development of sustainable and biodegradable materials is essential for future growth of the chemical industry. For a renewable product to be commercially competitive, it must be economically viable on an industrial scale and possess properties akin or superior to existing petroleum-derived analogs. Few biobased polymers have met this formidable challenge.

Two-stage transcriptional reprogramming in Saccharomyces cerevisiae for optimizing ethanol production from xylose.

Conversion of lignocellulosic material to ethanol is a major challenge in second generation bio-fuel production by yeast Saccharomyces cerevisiae. This report describes a novel strategy named "two-stage transcriptional reprogramming (TSTR)" in which key gene expression at both glucose and xylose fermentation phases is optimized in engineered S. cerevisiae.

A bio-catalytic approach to aliphatic ketones.

Depleting oil reserves and growing environmental concerns have necessitated the development of sustainable processes to fuels and chemicals. Here we have developed a general metabolic platform in E. coli to biosynthesize carboxylic acids.

Alteration of xylose reductase coenzyme preference to improve ethanol production by Saccharomyces cerevisiae from high xylose concentrations.

A K270R mutation of xylose reductase (XR) was constructed by site-direct mutagenesis. Fermentation results of the F106X and F106KR strains, which carried wild type XR and K270R respectively, were compared using different substrate concentrations (from 55 to 220 g/L). After 72 h, F106X produced less ethanol than xylitol, while F106KR produced ethanol at a constant yield of 0.

Afr1p mediates activation of the Slt2p MAP kinase induced by pheromone, heat shock and hypo-osmotic shock in Saccharomyces cerevisiae.

In this study, we reinvestigated the role of Afr1p in the regulation of pheromone signaling and demonstrated that pheromone signaling was not regulated by Afr1p because neither deletion nor overexpression of AFR1 affected alpha-factor-induced transcription induction of the FUS1 gene. The enhanced alpha-factor resistance resulting from overexpression of AFR1 was dependent on the Slt2p mitogen-activated protein kinase. We also found that alpha-factor-induced activation of Slt2p required Afr1p.

Afr1p has a role in regulating the localization of Mpk1p at the shmoo tip in Saccharomyces cerevisiae.

Afr1p functions to promote adaptation to pheromone-induced growth arrest and morphogenesis. We show here that Afr1p regulates polarized localization of the Mpk1p MAP kinase in shmooing cells. Deletion of AFR1 results in mislocalization of Mpk1p although the scaffold protein Spa2p localizes normally at shmoo tip, and overexpression of Spa2 cannot rescue this defect, indicating Afr1p in required for Spa2p to recruit Mpk1 to the site of polarized growth during mating.