Co-fermentation of xylose and cellobiose by an engineered Saccharomyces cerevisiae.

We have integrated and coordinately expressed in Saccharomyces cerevisiae a xylose isomerase and cellobiose phosphorylase from Ruminococcus flavefaciens that enables fermentation of glucose, xylose, and cellobiose under completely anaerobic conditions. The native xylose isomerase was active in cell-free extracts from yeast transformants containing a single integrated copy of the gene. We improved the activity of the enzyme and its affinity for xylose by modifications to the 5'-end of the gene, site-directed mutagenesis, and codon optimization.

Potential impact of synthetic biology on the development of microbial systems for the production of renewable fuels and chemicals.

Synthetic biology leverages advances in computational biology, molecular biology, protein engineering, and systems biology to design, synthesize, and assemble genetic elements for manipulating cell phenotypes. This emerging field is founded on a vast amount of gene sequence data available in public databases and our ability to rapidly and inexpensively synthesize DNA fragments of sufficient length to encode full-length genes, enzymes, metabolic pathways, and even entire genomes. Several thousand genetic elements encoding enzymes, reporters, repressors, activators, promoters, terminators, ribosome binding sites, signaling devices, and measurement systems are now available for engineering microbes.