مرکز منطقه ای اطلاع رساني علوم و فناوري -

چكيده لاتين :

Two different growth media, namely complex and defined media, were used to examine establishment of steady-state conditions in phosphate-limited culture system of Saccharomyces cerevisiae CENPKl13-5D strain. Using the defined growth medium, it was possible to obtain steady state condition in the continuous culture. The effect ofphosphate concentration on the growth of s. cerevisiae in phosphate-limited chemostat was studied at dilution rates between 0.08-0.45 h~J. The cellsי growth followed Monod kinetics only over low dilution rates (0.08-0.22 h-J) in which the saturation constant (Ks) and maximum growth rate (Pm) were determined as 10 pM and 0.25 «י, respectively. By increasing the dilution rates above 0.22 tcי, a significant change in the growth pattern was occurred, possibly due to intracellular accumulation of phosphate and/or extracellular accumulation ofethanol and also increasedfermentative activity ofthe yeast cells. Phosphate transport of the yeast cells via plasma membrane transporters was kinetically characterized in a phosphate-limited chemostat culture. The rate of phosphate transport was measured using 32[PJ-labeled orthophosphate in the concentration range of 0.4-2000 pM Highaffinity phosphate transport kinetics was observed over the entire range of dilution rates tested in this study. The corresponding K; values for phosphate were found to be in the range of I. 7 to 36 pM. Dilution rate of 0.22 h-1 showed biphasic pattern for phosphate uptake kinetics while the estimated K; values for this behavior were 1.7 and 284 pM