Production of sophorolipids in high concentration from deproteinized whey and rapeseed oil in a two stage fed batch process using Candida bombicola ATCC 22214 and Cryptococcus curvatus ATCC 20509

High concentrations of 422 g sophorolipids l(-1) were produced using a two-stage cultivation process: first deproteinized whey concentrate (DWC) containing 110 g lactose l(-1) was used for cultivation of the yeast Cryptococcus curvatus ATCC 20509, resulting in 34 g dry weight l(-1), 20 g single-cell oil l(-1) and reducing the chemical oxygen demand (COD) from 159 g l(-1) to 35 g oxygen l(-1). Afterwards cells were disrupted by passing the cell suspension directly through a high pressure laboratory homogeniser. After autoclavation, the resulting crude cell extract containing the single-cell oil served as substrate for growth of Candida bombicola ATCC 22214 and for sophorolipid production in a second stage. When the single-cell oil was consumed, repeated feeding of 400 g rapeseed oil l(-1) was started increasing the yield of sophorolipids to 422 g l(-1). A simple technique for product isolation, sedimentation, could be used to harvest the crude sophorolipids.