No abstract

Alkyl sophorosides, a special type of sophorolipids, can be produced using Candida bombicola cultures with glucose as main carbon source and 2-dodecanol as co-substrate. The dominating component, 2-dodecylsophoroside SL-E 2-12 , was purified via medium pressure liquid chromatography (MPLC) and used as substrate for further enzymatic modifications. Using b-glucuronidase in aqueous media the first modification gave a glycosidic cleavage of the acetyl glucose unit leading to 2-dodecyl-glucoside GL-A 2-12 . In a subsequent lipase-catalyzed acylation with sebacic acid in toluene this compound was functionalized regioselectively at the primary C-6 0 position of glucose. Similar lipase-catalyzed reactions in toluene, but now using SL-E 2-12 as acyl acceptor and unusual hydroxyl fatty acids -3-hydroxy decanoic acid and 17-hydroxy stearic acid -as acyl donors, resulted in mono-and diacylations of primary hydroxyl positions of the sophorose unit (C-6 0 and C-6 00 ) as shown by NMR and MS studies. In physicochemical characterization experiments the new glycoconjugates lowered the surface tension of water from 72 to 27-32 mN/m. Moreover it was observed that the new products inhibit the growth of particular Gram-positive bacteria. Additionally they indicate potential for anti-tumor promoting activity.Practical applications: According to literature data 2-alkyl-sophorosides can be produced using Candida bombicola cultures with yields of more than 20 g/L. Based on this starting material, 2-dodecyl-sophoroside, several regioselective enzymatic modifications were performed. Initially, b-glucuronidase catalysis in aqueous buffer solution gave 2-dodecyl-glucoside which was then successfully acylated at the C-6 position of glucose by lipase catalysis using a common dicarboxylic acid, sebacic acid. The resulting free carboxylic function of the acidic derivative opens up the possibility of achieving additional chemo-enzymatic reactions at this position for conversion, for instance, into polyesters. In addition lipase catalysis in organic solvents of 2-dodecyl-sophoroside allows acylation with unusual hydroxyl fatty acids of microbial origin. Physicochemical studies showed that these new glycoconjugates may be of interest for the cosmetic industry due to moisture conservation of the skin. For practical applications the conditions of the above biocatalytic reactions have been improved and scaled up.

To produce novel types of sophorose lipids containing an odd number of carbon atoms in the lipophilic moiety, Candida bombicola ATCC 22214 was grown in 500-ml flask cultures with glucose as main carbon source, and additionally, 2-tridecanone as co-substrate. After solvent extraction, the crude product mixture was separated into pure fractions, and each fraction was analysed via NMR and mass spectroscopy. This effective strategy generated five new glycolipids, 2-tridecyl sophorosides, which differed in the number of glucose units, and acetyl and hydroxy groups, respectively. Based on these compounds, a proposal for the possible biosynthetic pathway was deduced. Two compounds of the mixture, mono- and diacetylated 2-tridecyl sophorosides, respectively, were able to lower the surface tension of water from 72 mN m(-1) to 32 mN m(-1) and the interfacial tension between water and n-hexadecane from 43 mN m(-1) down to 4 and 3 mN m(-1). Thus, both compounds possess a very good surfactant behaviour. Moreover, it was observed that the new products inhibit the growth of particular Gram-positive bacteria, and they indicate potential for antitumour-promoting activity.

. Thus, both compounds possess a very good surfactant behaviour. Moreover, it was observed that the new products inhibit the growth of particular Gram-positive bacteria, and they indicate potential for antitumourpromoting activity.

hängigkeit und ¾nderung von Akzeptorlänge, Substratkonzentration und Enzymverhältnis weiter charakterisiert. Nach Optimierung der Synthese und der Aufreinigungsschritte wurde eine Ausbeute von 97 % erzielt und die Produktion wurde auf den 50-mg-Maûstab vergröûert.