Production of ethanol from l-arabinose by Saccharomyces cerevisiae containing a fungal l-arabinose pathway


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The fungal pathway for l-arabinose catabolism converts l-arabinose to d-xylulose 5-phosphate in five steps. The intermediates are, in this order: l-arabinitol, l-xylulose, xylitol and d-xylulose. Only some of the genes for the corresponding enzymes were known. We have recently identified the two missing genes for l-arabinitol 4-dehydrogenase and l-xylulose reductase and shown that overexpression of all the genes of the pathway in Saccharomyces cerevisiae enables growth on l-arabinose. Under anaerobic conditions ethanol is produced from l-arabinose, but at a very low rate. The reasons for the low rate of l-arabinose fermentation are discussed.