Fed-batch cultivation of bakers' yeast: effect of nutrient depletion and heat stress on cell composition.
The physiology of a commercial strain of bakers' yeast was studied in terms of the cell composition under different growth conditions and of its response to stress. The study comprised fed-batch experiments since this is the system used in bakers' yeast industry. The classical fed-batch fermentation procedure was modified in that the yeast cells were continuously grown to a steady-state at a dilution rate of 0.1/h in order to achieve more or less the same initial starting point in terms of cell composition. This steady-state culture was then switched to fed-batch concomitantly with exposure to stress. The highest amount of trehalose accumulation was achieved when nutrient depletion and heat stress were applied concomitantly. The highest amount of trehalose, 12%, was attained in cells stressed by both nitrogen depletion and heat stress. The protein content remained constant, although with some oscillations, at a value of 30% throughout this dual stress experiment.
Ertugay
N
N
Department of Food Engineering, Middle East Technical University, Ankara, Turkey.
Hamamci
H
H
Bayindirli
A
A
D018533:Biomass; D005656:Fungal Proteins / Q000032:analysis; D006358:Hot Temperature; D009584:Nitrogen / Q000172:deficiency; D010710:Phosphates / Q000172:deficiency; D012441:Saccharomyces cerevisiae / Q000502:physiology*
D005656:Fungal Proteins; D010710:Phosphates; D009584:Nitrogen