Kinetics and balance of a fermentation free from product inhibition: sophorose lipid production by Candida bombicola

Abstract

The production of sophorose lipids from ethyl esters of rapeseed oil fatty acids and glucose by Candida bombicola CBS 6009 was studied. A kinetic description of the fermentation is presented, showing in particular two distinct phases of growth and, following nitrogen limitation, subsequent production of sophorose lipids, which were excluded from the aqueous phase. With the fed-batch fermentation technology used, a high production performance (320 g·l−1 sophorose lipids with a weight yield of 65% with respect to the carbon sources) was obtained. Detailed fermentation balances were established and their implications for energy metabolism during glycolipid production are discussed. The variations in the structure of the sophorose lipids during fermentation were also studied. Sophorolipid 1′, 4″-lactone 6′, 6″-diacetate was the major class compound produced (about 50% of the glycolipids). A correlation between the lipidic composition of the products and the nature of the fatty acids of the rapeseed esters was observed.