Properties of sophorolipid produced by the yeast Candida bombicola grown on different lipophilic carbon substrates

Abstract

In the present study, sophorolipids were produced by yeast Candida bombicola ATCC 22214 when cultured on various lipophilic carbon substrates, such as oleic acid, rapeseed oil, cottonseed oil, and frying waste oil. The structure and surface active properties were investigated. Fed-batch fermentations of Candida bombicola resulted in sophorolipids yields of 101, 73 and 51 g·L-1 from oleic acid, rapeseed oil, and cottonseed oil. The structures of individual sophorolipid components were quantified and identified by HPLC-MS/MS system. Results showed that the products were heterogeneous mixtures of acetylated lactonized and acidic sophorolipids, and the large majority of the sophorolipids existed in the lactonic forms. Among the lactonized sophorolipids, the predominant component is sophorolipid containing hydroxyoleic acid (C18:1) as the lipid moiety. Sophorolipids had high surface activity, such as low surface tension and CMC and good stability. The minimum surface tension of the produced sophorolipids in aqueous solution were found to be 36.0—37.0 mN·m-1 regardless of the carbon substrates while disparity occurred in the CMC values. Unhindered surface activity of the sophorolipids was found at wide range of pH(2—10), temperature (heating at 100 ℃ for 2 h) and salt concentrations (0—20% NaCl).