Yeast engineering for sugar acid production
Tuesday, April 29, 2014: 3:10 PM
Grand Ballroom D-E, lobby level (Hilton Clearwater Beach)
Yvonne Nygård, Mervi Toivari, Laura Ruohonen, Merja Penttilä and Marilyn G. Wiebe, VTT Technical Research Centre of Finland, Espoo, Finland
Various organic acids have huge potential as industrial platform chemicals. Biotechnological routes of organic acid production are currently being sought, so that fossil resources and petrochemistry could be replaced with renewable resources. Microbial production of organic acids can provide an environmentally sound, sustainable way of producing industrial chemicals.

Bio-based production of sugar acids requires the enhancement of production via existing biosynthetic pathways, reduction of carbon loss to alternative by-products, and/or addition of new biosynthetic routes to suitable production hosts. In addition, microbial physiology and environmental conditions for high production levels are considered and optimized. Production of acids imposes stresses on the organism and these stresses affect the vitality, viability and productivity of the cells in a bioprocess. Understanding the physiology of micro-organisms which have been genetically engineered to produce an organic acid, can make valuable contributions to the development of production organisms for biorefineries.

VTT has been studying and developing the production of several novel acids derived from the sugars of plant biomass hydrolysates. Among these is D-xylonic acid derived from the 5-carbon sugar D-xylose. D-Xylose is a major component of hemicellulose present in lignocellosic materials. Production of D-xylonic acid was developed to serve as a model system for studying acid production in yeast. Several yeast species, including industrial Saccharomyces cerevisiae and Pichia kudriavzevii have been engineered for or D-xylonate production. P. kudriavzevii was capable of producing 171 or 146 g D-xylonate l-1, at a rate of 1.4 or 1.2 g l-1 h-1, at pH 5.5 or pH 3, respectively.