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 observed only when the SCF was operated with an extended phase of fermentation at the end of each cycle. A new control strategy was developed to allow the production of sophorolipids by coupling the fermentation control to the secondary metabolism of the culture. Cycling was controlled by the complete exhaustion of either hexadecane or sunflower oil, one of the nutrients utilized for the secondary metabolism. A new, repeatable pattern of dissolved oxygen concentration, the main control parameter, was observed. Stable, synchronous cultures were obtained with the cycle time of the fermentation approximately 2 h longer than the doubling time of the micro-organism. The doubling time of the culture was not adversely affected by the addition of an extended phase of growth at the end of the cycles. The number of viable cells was also observed to remain constant throughout the extended phase of fermentation.