KINETICS OF LACTOSE TRANSPORT IN KLUYVEROMYCES-FRAGILIS GROWN IN A CHEMOSTAT ON DILUTED WHEY PERMEATE

Lactose transport was studied in Kluyveromyces fragilis grown in lacto se-limited chemostat cultures, Kinetic parameters were determined usin g a method based on genetic population evolution. Lactose transport wa s carried out via three carriers characterized respectively by K-m of 0.1 mM, 3 mM and 15.5 mM, The synthesis of these lactose carriers and their capacity (V-max) are dependent on the dilution rate (D), At D = 0.12 h(-1), the high affinity transporter is prominent, For intermedia te dilution rate, only the high and the medium affinity systems are pr esent, In cells growing at D = 0.4 h(-1), these carriers are absent bu t instead, the low affinity transporter is present, The effect on lact ose transport of such metabolic inhibitors as CCCP, a proton ionophore , and Antimycin A, an energy inhibitor, were also investigated, The hi gh affinity system is the most sensitive to the effect of these inhibi tors, Lactose transport through this carrier is probably a mechanism d ependent on the proton motive force.