Super-yeast generates ethanol from energy crops and agricultural residues

A new type of baker's yeast (Saccharomyces cerevisiae) has been developed which can efficiently ferment pentose sugars, as found in agricultural waste and hardwoods. Researchers writing in BioMed Central's open access journal Biotechnology for Biofuels describe the creation of the new S. cerevisiae strain, TMB3130, which demonstrated significantly improved aerobic growth rate and final biomass concentration on sugar media composed of two pentoses, xylose and arabinose.

Marie Gorwa-Grauslund, from Lund University, Sweden, worked with an international team of researchers to generate the novel micro-organism. She said, "To the best of our knowledge, this is the first report that characterizes molecular mechanisms for improved mixed-pentose utilization obtained by evolutionary engineering of a recombinant S. cerevisiae strain".

Normal baker's yeast cannot ferment pentose sugars at all. By inserting the required genes from other fungi and bacteria it is possible to make a relatively inefficient transgenic strain that can ferment pentose sugars. Gorwa-Grauslund and her colleagues took one of these recombinant strains, TMB3061, and grew it on a mixture of xylose and arabinose sugars in order to select a stable population most capable of metabolising the pentose feedstock. She said, "There is considerable interest in developing 'second-generation' biofuels to refine and upgrade non-food material, especially dedicated energy crops and agricultural residues such as straw, bagasse, stover and corn hulls. Our yeast demonstrates a significant step towards this goal."

1. Improved xylose and arabinose utilization by an industrial recombinant Saccharomyces cerevisiae strain using evolutionary engineering
Rosa Garcia Sanchez, Kaisa Karhumaa, César Fonseca, Violeta Sànchez Nogué, João RM Almeida, Christer U Larsson, Oskar Bengtsson, Maurizio Bettiga, Bärbel Hahn-Hägerdal and Marie F Gorwa-Grauslund
Biotechnology for Biofuels (in press)

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