SOPHOROSE LIPID FERMENTATION WITH DIFFERENTIATED SUBSTRATE SUPPLY FORGROWTH AND PRODUCTION PHASES

Sophorose lipid production by Candida bombicola is a two-step process where sophorose lipids are mainly produced after a first stage of grow th, ending because of nitrogen limitation. The influence of the follow ing parameters was individually studied for both the stages of growth and of product formation with respect to final sophorose lipid product ion performance: pH, temperature and carbon source. Glucose and rapese ed ethyl esters were supplied individually or as a dual carbon source. The lipidic substrate was added by continuous feeding. It was found t hat supplying both carbon sources during the production step was cruci al for obtaining a high production performance ranging from 250 g l(-1 ) to 300 g l(-1) or more. Controlling the feeding of rapeseed ethyl es ters to avoid inhibition by fatty acids was essential for a successful scale-up of the fermentation on the industrial scale. The conditions of substrate feeding markedly affected the composition of the mixture of sophorose lipids produced, namely the extent of acetylation of the sophorose moieties and distribution of the acidic and lactonic forms. The results suggest that the physiological role of sophorose lipid pro duction is related to the regulation of energy metabolism.