9-21: Engineering Saccharomyces cerevisiae for production of glycolic acid

Tuesday, May 1, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
Outi M. Koivistoinen, Joosu Kuivanen, Merja Penttilä and Peter Richard, VTT Technical Research Centre of Finland, Espoo, Finland
Glycolic acid is the smallest alpha-hydroxy acid and is used in a wide range of chemical processes, in cosmetics and as a precursor for biopolymers. Currently glycolic acid is produced by chemical synthesis, for example, from chloroacetic acid. However, from a sustainable point of view a biotechnological production route would be more desirable. Glycolic acid production from lignocellulosic second generation biomass feedstocks would be sustainably and perhaps as well economically better solution.

Our approach was to use genetically engineered S. cerevisiae to develop a fermentation based method for glycolic acid production. Glycolic acid can be produced in the glyoxylate cycle where glyoxylate can be further converted to glycolic acid. S. cerevisiae has a gene coding for glyoxylate reductase but in order to make the conversion more efficient we overexpressed an NADPH specific glyoxylate reductase from Arabidobsis thaliana for converting glyoxylate to glycolic acid.

For efficient conversion of glyoxylate into glycolic acid and boosting up the glyoxylate cycle also further modifications were made. Two malate synthase genes were deleted to prevent glyoxylate to react to malate. Additionally steps leading to glyoxylate formation were boosted by overexpressing isocitrate lyase and aconitase. Also the influence of regulatory factors, effect of ethanol metabolism and acetyl-CoA and NADPH availability were tested. The resulting strains were cultivated in shake flasks in different media and the production of glycolic acid was demonstrated.

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