Sophorolipid production by Candida bombicola: Medium composition and culture methods

Candida bombicola is able to produce sophorolipid molecules with surfactant properties when grown in a medium composed of two different carbon sources (usually sugar and oil) and a nitrogen source (frequently yeast extract). In this work, the composition of the medium and the culture method employed have been studied. The influences of glucose concentration, properties of oil and yeast extract concentration have been taken into account. According ly, a production medium composition is proposed (100 g/l glucose, 100 g/l s unflower oh and I g/l yeast extract). The most frequent culture methods rep orted in Literature, i.e. batch, medium pulse mode and resting-cell methods , have been tested. The resting-cell method was found to produce the highes t final concentration of sophorolipid, obtaining a good yield of carbon sou rces in a relatively short time. Under the best operational conditions and using the resting-cell method, 120 g/l sophorolipid was obtained in 8 d, wi th a carbon source yield of 0.60. Product distribution has also been invest igated and the sophorolipid molecular structure of opened or cycled molecul es has been determined under different operational conditions. Low yeast ex tract concentration and long fermentation time enhance the production of cy cled structures by all the production methods studied.