A variable volume fed-batch culture was adopted (incremental feeding of same concentration solution to that of initial medium resulting in an increase in volume). All the fermentations were performed in a fed-batch mode in a 5-l bioreactor controlled by a computer having advanced fermentation soft water. The fermenter was equipped with temperature, agitation, and aeration systems with precise control for these parameters. Aeration was measured in terms of dissolved oxygen. The parameters were measured and automonitored against the set values. The pH was, however, controlled manually by adding acid or alkali as the case may be. The volume of incremental feeding was adjusted in such a way that the final volume in the fermenter reached to about 4.75-5.00 l. The samples were drawn using sampling port at a 2-h interval during fermentation using injection syringe under aseptic conditions. Incremental feeding was started after 1 h of actual start of fermentation (called as activation period) and stopped before 1 h of actual completion of fermentation (called as terminal cell maturity step). For incremental feeding additional accessories were attached to the fermenter. Generally, 7-8 h were taken by incremental feeding at this rate. The fermentation parameters were kept arbitrary but constant, except that used for standardization during the parameter optimization experiments.