title: Insufficient uracil supply in fully aerobic chemostat cultures of Saccharomyces cerevisiae leads to respiro-fermentative metabolism and double nutrient-limitation.
abstract: A combination of chemostat cultivation and a defined medium was used to demonstrate that uracil limitation leads to a drastic alteration in the physiology of auxotrophic cells of Saccharomyces cerevisiae. Under this condition, the carbon source is dissimilated mainly to ethanol and acetate, even in fully aerobic cultures grown at 0.1 h(-1), which is far below the critical dilution rate. Differently from nitrogen-, sulphur-, or phosphate-limited cultures, uracil limitation leads to residual sugar (either glucose or sucrose) concentrations below 2 mM, which characterizes a situation of double-limitation: by the carbon source and by uracil. Furthermore, the specific rates of CO2 production and O2 consumption are increased when compared to the corresponding prototrophic strain. We conclude that when auxotrophic strains are to be used for quantitative physiological studies, special attention must be paid to the cultivation conditions, mainly regarding medium formulation, in order to avoid limitation of growth by the auxotrophic nutrient.
authors.affiliation: Department of Chemical Engineering, University of São Paulo, C.P. 61548, 05424-970, São Paulo, SP, Brazil.
authors.forename: Thiago Olitta
authors.initials: TO
authors.lastname: Basso
authors.forename: Marcelo Goulart
authors.initials: MG
authors.lastname: Dario
authors.forename: Aldo
authors.initials: A
authors.lastname: Tonso
authors.forename: Boris Ugarte
authors.initials: BU
authors.lastname: Stambuk
authors.forename: Andreas Karoly
authors.initials: AK
authors.lastname: Gombert
mesh_terms: D019342:Acetic Acid / Q000378:metabolism; D000332:Aerobiosis; D050260:Carbohydrate Metabolism; D002244:Carbon / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry; D000431:Ethanol / Q000378:metabolism; D005285:Fermentation; D010101:Oxygen Consumption; D012441:Saccharomyces cerevisiae / Q000254:growth & development* / Q000378:metabolism*; D014498:Uracil / Q000378:metabolism*
chemical_list: D003470:Culture Media; D002245:Carbon Dioxide; D000431:Ethanol; D014498:Uracil; D002244:Carbon; D019342:Acetic Acid