Production of sophorolipids from whey II. Product composition, surface active properties, cytotoxicity and stability against hydrolases by enzymatic treatment

Sophorolipids. obtained by a two-stage process starting from deproteinized whey concentrate using Cryptococcus curvatus ATCC 20509 and Candida bombico la ATCC 22214, were compared to products from one-stage processes, using di fferent lipidic compounds as substrates. Results showed that above all carb on source and not cultivation conditions had a distinct influence on the co mposition of the crude product mixture and therefore on the physicochemical and biological properties of the sophorolipids, such as, for example, surf ace activity, cytotoxicity and stability against hydrolases. The results we re completed by corresponding data for purified mono- and diacetylated (17- hydroxyoctadecenoic)-1',4 "-lactonized sophorolipids. Crude sophorolipid mi xtures showed moderate to good surface active properties (SFTmin 39 mN m(-1 ), CMC 130 mg l(-1)), water solubilities (2-3 g l(-1)) and low cytotoxiciti es (LC50 300-700 mg l(-1)). In contrast, purified sophorolipids were more s urface active (SFTmin 36 mN m(-1), CMC 10 mg l(-1)), less water soluble (ma x. 70 mg l(-1)) and showed stronger cytotoxic effects (LC50 15 mg l(-1)). I ncubation of crude sophorolipid mixtures with different hydrolases demonstr ated that treatment with commercially available lipases such as from Candid a rugosa and Mucor miehei distinctly reduced the surface active properties of the sophorolipids, while treatment with porcine liver esterase and glyco sidases had no effect.