Genome structures hold secrets to boosting bioethanol production?

The genome structures of biofuel yeasts could hold answers to increasing worldwide fuel ethanol production, scientists said today, based on two recent studies in Genome Research.

Bioethanol comes from fermenting plant material, such as sugar cane and corn, with the hardy yeast Saccharomyces cerevisae, which adapts in the industrial environment (see Making yeast beefier).

Researchers said they are looking to identify genetic changes that underlie this adaptation, with the potential to engineer new, more robust yeast strains that could help to increase bioethanol production on a global level.

Researcher Lucas Argueso and colleagues from Duke University and Brazil sequenced and analyzed the structure of the entire genome of strain PE-2, a well-known industrial strain in Brazil.

They found chromosomal rearrangements in PE-2 amplified genes allowed for their stress tolerance, which likely contributed to the adaptation of this strain to the industrial environment. They said the strain is amenable to genetic engineering, which could lead to developing new technologies to boost bioethanol production.

Researchers from Stanford University and Brazil, led by Boris Stambuk and Gavin Sherlock, analyzed the genome structure of industrial bioethanol yeasts, looking for variations in the number of gene copies in five strains employed in Brazil, including PE-2. They found all the  strains had amplifications of genes involved in the synthesis of vitamins B6 and B1, which are needed for efficient growth and utilization of sugar.

They showed in their experiments gene amplifications confer robust growth in industrial conditions, proving these yeasts likely adapt to limited availability of vitamins in the industrial process.

Their research suggests this information could be used to engineer new yeast strains capable of more efficient bioethanol production, from a wider range of feedstocks.

Companies such as Emeryville, Calif.-based Amyris Biotechnologies are making biofuels and chemicals from synthetic microorganisms (see Amyris pulls in $70M for unique biofuel and Amyris Biotechnologies evolving ethanol).

By altering the metabolic pathways of yeast, Amyris said it is able to engineer "living factories" that convert sugar cane into chemicals and renewable fuels, which it said have performance attributes comparable to petroleum-based products.

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