SOPHOROLIPIDS PRODUCTION BY CANDIDA-BOMBICOLA USING SELF-CYCLING FERMENTATION

The self-cycling fermentation (SCF) technique was applied to cultures of Candida bombicola. Sophorolipids, secondary metabolites, were obser ved only when the SCF was operated with an extended phase of fermentat ion at the end of each cycle. A new control strategy was developed to allow the production of sophorolipids by coupling the fermentation con trol to the secondary metabolism of the culture. Cycling was controlle d by the complete exhaustion of either hexadecane or sunflower oil, on e of the nutrients utilized for the secondary metabolism. A new, repea table pattern of dissolved oxygen concentration, the main control para meter, was observed. Stable, synchronous cultures were obtained with t he cycle time of the fermentation approximately 2 h longer than the do ubling time of the micro-organism. The doubling time of the culture wa s not adversely affected by the addition of an extended phase of growt h at the end of the cycles. The number of viable cells was also observ ed to remain constant throughout the extended phase of fermentation.