title: Physiological behaviour of Saccharomyces cerevisiae in aerated fed-batch fermentation for high level production of bioethanol.
abstract: Saccharomyces cerevisiae was able to produce 20% (v/v) of ethanol in 45 h in a fully aerated fed-batch process recently developed in our laboratory. A notable feature of this process was a production phase uncoupled to growth, the extent of which was critical for high-level ethanol production. As the level of production was found to be highly variable, we investigated on this high variability by means of a detailed physiological analysis of yeast cells in two fed-batch fermentations showing the most extreme behaviour. We found a massive leakage of intracellular metabolites into the growth medium which correlated with the drop of cell viability. The loss of viability was also found to be proportional to the reduction of plasma membrane phospholipids. Finally, the fed-batch processes with the longest uncoupling phase were characterized by induction of storage carbohydrates at the onset of this phase, whereas this metabolic event was not seen in processes with a short uncoupling phase. Taken together, our results suggested that reproducible high-level bioethanol production in aerated fed-batch processes may be linked to the ability of yeast cells to impede ethanol toxicity by triggering a metabolic remodelling reminiscent to that of cells entering a quiescent GO/G1 state.
authors.affiliation: Laboratoire de Biotechnologie & Bioprocédés, UMR-CNRS 5504, UMR-INRA792, Institut National des Sciences Appliquées, Avenue de Rangueil, Toulouse Cedex 04, France.
authors.forename: Marlène
authors.initials: M
authors.lastname: Cot
authors.forename: Marie-Odile
authors.initials: MO
authors.lastname: Loret
authors.forename: Jean
authors.initials: J
authors.lastname: François
authors.forename: Laurent
authors.initials: L
authors.lastname: Benbadis
mesh_terms: D000222:Adaptation, Physiological; D000332:Aerobiosis; D019149:Bioreactors; D003470:Culture Media; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D015966:Gene Expression Regulation, Fungal; D007218:Industrial Microbiology / Q000379:methods; D012441:Saccharomyces cerevisiae / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*
chemical_list: D003470:Culture Media; D000431:Ethanol