No abstract

By aid of lipases, e.g. of Mucor miehei, in n-hexane wax esters were produced from usual primary fatty alcohols and unusual hydroxy fatty acids (in part of microbial origin). Thus, (S)-17-hydroxyoctadecanoic acid dodecyl ester and (Ri-3-hydroxy decanoic acid dodecyl ester were formed. I n measurements of the film pressure using a LANGiMUIR film balance the monolayers of both compounds indicated good stability compared to the non-hydroxy wax esters. Glycolipids de novo produced by microorganisms did not show suitable wetting properties, but they were able to lower Le surface tension of water to a higher extent than the unusual waxes.

Wax esters from fatty alcohols and uncommon fatty acids were synthesized in yields up to 90% when commercially available microbial lipases from Rhizomucor miehei (Lipozym ewM) and Candida antarctica (SP 435) were used with limited water content in nonpolar solvents under mild conditions. The corresponding fatty acids were prepared by chemical conversion of naturally occurring resources (agricultural surpluses). Also, when phenylboronic acid was added as solub'dizing agent in a nonpolar solvent, the direct enzymatic monoacylation of glycerol with uncommon fatty acids was successful. The measurement of n/A-isotherms by means of a Langmuir film balance indicated medium film pressures, medium or large molecular areas, and interesting phase behavior. The monolayer of a wax ester at the air/water interface could be directly visualized by Brewster angle microscopy.KEY WORDS: n/A-isotherms, Brewster angle microscopy, film pressure, glycerol, lipase, monoacylation, nonaqueous conditions, uncommon wax esters.

Results on the enzymatic monoacylation of glycerol by aid of phenylboronic acid in organic solvents are presented. The comparison of two alternative methods indicates that the "2-step-method" (synthesis in one batch unit without isolation of intermediates) is in total more favourable than the "3-step-method" (synthesis in two batch units including isolation of intermediates), although yields are somewhat lower. Probably this disadvantage originates from an enzyme inhibition caused by residual free phenylboronic acid in the reaction system. Several varying uncommon fatty acids like (S)-17-hydroxyoctadecanoic acid, 12-hydroxyoctadecanoic acid and 2-hydroxyhexadecanoic acid have been used as oleo-components. As far as no steric hindrance is caused by these substrates, product formation is about 80% (basis "2-step-method"). Investigations at the Langmuir film balance showed different film states with specific transition phases for the l(3)-(17-hydroxy)-octadecanoyl and the l(3)-( 12-hydroxy)-octadecanoyl glycerol. The monoglyceride of the 2-hydroxyhexadecanoic acid proved to be a good emulsifier. Its qualities in this respect were confirmed by the data of the surface and interfacial tension versus n-hexadecane and also by the outcome of the emulsification tests. The enzymatic acylation of a diol like 1.3-propanediol led to the 1-(17-hydroxy)-octadecanoyl-3-propanol (yield: 50%). The film behaviour of this ester was similar to that of the corresponding monoglyceride. '

Mil Blick auf eine gezielte Herstellung von ungewöhnlichen Wachsestern, die in der Natur in solcher Zusammensetzung überhaupt nicht oder nur in geringen Mengen vorkommen und mit chemischen Methoden nur unter großem Aufwand produziert werden können, wird der Einsatz von Biokatalysatoren in den Mittelpunkt dieses Artikels gerückt. Unter Verwendung von Lipasen in aprotischen Lösungsmitteln oder lösungsmittelfrei wurde eine Reihe von ungewöhnlichen, d. h. substituierten, Fettsäuren mit z. T. ebenfalls ungewöhnlichen Fettalkoholen unter milden Bedingungen verestert. Eine besonders große Vielfalt an Molekülstrukturen ist erstellt worden auf dem Gebiet der Hydroxy‐Wachsester, deren Filmdruck‐Eigenschaften sie für die Verwendung als Netzmittel im Bereich der Kosmetik, Pharmazeutik oder der Farben und Lacke interessant machen.