Physiological responses to acid stress by Saccharomyces cerevisiae when applying high initial cell density.
High initial cell density is used to increase volumetric productivity and shorten production time in lignocellulosic hydrolysate fermentation. Comparison of physiological parameters in high initial cell density cultivation of Saccharomyces cerevisiae in the presence of acetic, formic, levulinic and cinnamic acids demonstrated general and acid-specific responses of cells. All the acids studied impaired growth and inhibited glycolytic flux, and caused oxidative stress and accumulation of trehalose. However, trehalose may play a role other than protecting yeast cells from acid-induced oxidative stress. Unlike the other acids, cinnamic acid did not cause depletion of cellular ATP, but abolished the growth of yeast on ethanol. Compared with low initial cell density, increasing initial cell density reduced the lag phase and improved the bioconversion yield of cinnamic acid during acid adaptation. In addition, yeast cells were able to grow at elevated concentrations of acid, probable due to the increase in phenotypic cell-to-cell heterogeneity in large inoculum size. Furthermore, the specific growth rate and the specific rates of glucose consumption and metabolite production were significantly lower than at low initial cell density, which was a result of the accumulation of a large fraction of cells that persisted in a viable but non-proliferating state.
Department of Biology and Biological Engineering, Division of Industrial Biotechnology, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
Zhong-Peng
ZP
Guo
Department of Biology and Biological Engineering, Division of Industrial Biotechnology, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden lisbeth.olsson@chalmers.se.
Lisbeth
L
Olsson
D000255:Adenosine Triphosphate / Q000378:metabolism; D002264:Carboxylic Acids / Q000633:toxicity*; D000431:Ethanol / Q000378:metabolism; D006019:Glycolysis / Q000187:drug effects; D018384:Oxidative Stress; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology*; D013312:Stress, Physiological; D014199:Trehalose / Q000378:metabolism
D002264:Carboxylic Acids; D000431:Ethanol; D000255:Adenosine Triphosphate; D014199:Trehalose
Saccharomyces cerevisiae; high initial cell density; low initial cell density; physiological response; weak acids