A colony of the fungus Neurospora crassa grows on cellulose (left). Neurospora crassa sugar transport molecules incorporated into the yeast are labeled with green fluorescent proteins (right). (Credit: Jamie Cate and Susan Jenkins, UC Berkeley & EBI)
Reading Researchers have succeeded in combining the abilities of a fungus that metabolizes plant fibers with those of alcohol-producing yeast to create yeast strains that form cellulose alcohol by digesting the resistant plant material. Their method could be of great use for ethanol production in the biofuel industry, because so far ethanol can not yet be extracted from vegetable fibers. Up to now biofuel production has been based on simple brewer's yeast, which can turn sugar or maize starch into ethanol through fermentation processes. Vegetable fibers have hitherto been unable to utilize the yeasts because they contain cellulose, an organic compound in cell walls that consists of tightly linked sugar molecules and that the yeast fungus can not break up. In order to digest these resistant sugar chains, they would first have to be broken up into smaller pieces and then fragmented by further processes into even smaller parts, the so-called glucose. Because the yeast fungus can metabolize only glucose, a simple sugar. Other fungi, on the other hand, are able to digest plant fibers as well. The disadvantage: these mushrooms do not produce alcohol during the feeding process.

The research team led by Jonathan Galazka of the University of California at Berkeley has now been able to identify the responsible genes for the cellulose digestion of fungi of the genus Neurospora crassa and to incorporate them into the yeast. The genetically manipulated yeast fungi were able to digest plant fibers and thereby produced ethanol as a metabolite: "With this trick we were able to produce yeast strains that grow better than untreated yeast on plant fibers, " explains one of the scientists.

In the biofuel industry, efforts have long been made to find alternatives to alcohol extraction from corn starch or sugar. With genetically manipulated yeast, it is now also possible to extract ethanol from waste products containing plant fibers, such as grain stalks, leaves or paper waste, and thus no longer rely on valuable agricultural land.

Jonathan Galazka (University of California, Berkeley) et al .: Science, Online Preliminary Publication, doi: 10.1126 / science.1192838 dapd / wissenschaft.de - Kristina Abel's Ad

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