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Triacetic acid lactone production in industrial Saccharomyces yeast strains

Lauren P. Saunders, Michael J. Bowman, Jeffrey A. Mertens, Nancy A. Da Silva, Ronald E. Hector
Journal of industrial microbiology & biotechnology 2015 v.42 no.5 pp. 711-721
Saccharomyces, acetates, bioreactors, carbon, ethanol, genes, genetic background, glucose, glycerol, industrial microbiology, lactones, metabolic engineering, strains, yeasts
Triacetic acid lactone (TAL) is a potential platform chemical that can be produced in yeast. To evaluate the potential for industrial yeast strains to produce TAL, the g2ps1 gene encoding 2-pyrone synthase was transformed into 13 industrial yeast strains of varied genetic background. TAL production varied 63-fold between strains when compared in batch culture with glucose. Ethanol, acetate, and glycerol were also tested as potential carbon sources. Batch cultures with ethanol medium produced the highest titers. Therefore, fed-batch cultivation with ethanol feed was assayed for TAL production in bioreactors, producing our highest TAL titer, 5.2 g/L. Higher feed rates resulted in a loss of TAL and subsequent production of additional TAL side products. Finally, TAL efflux was measured and TAL is actively exported from S. cerevisiae cells. Percent yield for all strains was low, indicating that further metabolic engineering of the strains is required.