No description available.

This diploma thesis deals with the microbial production of sophorolipids by the Starmerella genus yeasts. The theoretical part of the thesis includes general characteristics of biosurfactants with the focus on sophorolipids. There are described the options of biotechnological production of sophorolipids and fields of their possible applications. Furthermore, the theoretical part deals with the describtion of Starmerella bombicola yeast, which is often used for biotechnological production of sophorolipids. Six strains of the Starmerella genus were cultured in the basic medium suitable for sophorolipid produsction. The amount of produced sophorolipids was tested by the emulsification capacity assay, solubilization of crystalline anthracene assay, measuring the surface tension by the Du-Noüy-Ring method and determination of the sophorolipid concentration by extraction with ethyl acetate. The purity of the extracted sophorolipids was inspected by the Fourier Transform infrared spectrosopy (FT-IR) Based on the results, the Starmerella bombicola CBS 6009 and the Starmerella anomalae CBS 14178 strains were studied in greater detail. They were cultured in several production media of different composition and the effect of the individual components on the ability of the sophorolipid production was monitored. Based on the results, it was evaluated that the composition of the medium has a great influence on the production ability of the strains. The highest production rate of sophorolipids was achieved in the basic production medium and so was in the medium containing molasses and Indian waste oil. The cultivation mode has great effect on the sophotolipid production rate. It has been found that when cultured in a bioreactor, the strains produced sophorolipids in a larger amount and of a different quality than in the shaker flasks.

The employment of enzymes and whole cells has been important in many industries for centuries. However, it is only in the last 30 years that the use of enzymes for the synthesis of high-value fine chemicals has enjoyed increasing popularity. In fact, esterases and lipases are used almost routinely these days to provide optically active building blocks for the construction of imaginative new routes to chiral target molecules. The major topic of this work describes the utilization of enzymes (namely lipases) in the synthesis and modification of natural and non-natural compounds. Chapter 1 outlines the strengths and weaknesses of the most widely used enzyme systems and a description of a brief summary on the state of the art of biotransformations with special emphasis on the general applicability and reliability of various reaction types is described. Chapter 2 describes the enzymatic resolution of various 3-acetoxy-4-aryl-substituted azetidin-2-ones. Following screening of enzymes, such as Novozym-435, PS-30, PPL and AYS the best conditions were a phosphate buffer with PS-30 as the enzyme. The resulting products were the (3S, 4R)-3-hydroxy-4-aryl-substituted azetidin-2-ones and the unreacted (3R, 4S)-3-acetoxy-4-aryl-substituted azetidin-2-ones. Reactions generally occurred with high conversion and high selectivity. In Chapter 3, the regioselective transesterifications and hydrolysis of peracylated sophorolipid (SL) derivatives catalyzed by lipases was investigated. It was confirmed from the detailed spectral analysis of the products that transesterification failed to furnish any free hydroxyls on the sophorose ring. Instead, transesterification took place on the methyl ester located at the carboxylic end of the 17-hydroxyoctadecenoic acid chain attached to the C-1' position of the sophorose ring. In Chapter 4, the chemo-enzymatic syntheses of enantiomerically pure R and S imperanene from vanillin are described. The key step entails the asymmetrization of a prochiral diol using lipase PS-30. The resulting monoacetate has enantiomeric excesses of >97%. Biocatalysts represent a new class of chiral catalysts useful for a broad range of selective organic transformations. It is stating the obvious to say that biocatalysis is not a panacea for synthetic organic chemistry. However, advances over the past thirty years mean that it would be a serious mistake not to consider the employment of a biocatalyst, in, perhaps, the key step in a sequence of transformations that turn a cheap starting material into an expensive fine chemical.

Les sophorolipides, appartenant à la famille des glycolipides produits par voie microbienne à l'échelle industrielle, possèdent un groupement COOH sensible au pH qui leur confèrent des propriétés d'auto-assemblage uniques. Dans ce travail, nous avons étudié deux variantes de cette molécules, une avec une chaîne alkyle saturée (C18:0 SL) et une avec des groupes acétyles sur la partie sucrée (C18:1a SL). Le C18:0 forme des rubans chiraux à pH < 7.5 que nous avons caractérisés avec des techniques de cryo microscopie, diffusion de la lumière, des neutrons et des rayons-X et de la RMN solide. Le composé mono-insaturé C18:1cis, étudié dans la littérature, s'auto-organise en micelles et ellipsoïdes sous les mêmes conditions que le C18:0 forme des rubans. A pH basique, la charge négative sur le COOH conduit à la formation de plaquettes pour les deux SL, C18:0 et C18:1cis. La molécule acétylée, C18:1a, ressemble dans son comportement au C18:1cis et forme des ellipsoïdes dont la longueur peut être modifiée avec le pH. Finalement, nous avons étudié l'effet du C18:0 sur la prolifération de cellules fibroblastes, pour une éventuelle application dans la cicatrisation de la peau. / Sophorolipids (SL), a family of industrially-scaled bolaform microbial glycolipids, possess a pH-sensitive COOH group and are expected to exhibit a unique self-assembly behavior. In this work, we have studied 2 different types of this molecule, whose chemical structure has been modified on the alkyl chain (leading to the saturated C18:0 SL) and on the sophorose moiety (leading to the acetylated C18:1a SL). The C18:0 SL forms chiral nanofibers only at pH below 7.5 and we have characterized them with powerful techniques such as cryo-TEM, light, neutron and X-Ray scattering and solid state NMR. Interestingly, the mono-unsaturated compound (C18:1cis) self-organizes into micelles and ellipsoids under the same conditions (pH < 7.5), as reported in the literature. At basic pH, the negative charge on the COOH group drives the self-assembly towards platelet-like objects for both, C18:0 and C18:1cis SL. The acetylated compound C18:1a resembles the C18:1cis SL and forms ellipsoids, whose length can be triggered with the pH. Finally, we have investigated cell viability tests of C18:0 SL to human cells (fibroblasts) in vitro for potential wound healing applications of this biosurfactant.

This diploma thesis focuses on a research of the foam stability of the beer. We specifically observed the influence of ethanol and surface tension on the foam stability, and influence of ethanol and surface tension on the height of the foam. It was observed the influence of the hop acids in non-alcoholic beers. Furthermore, different biosurfactants were added into to the beer to observe better stability of the foam. The theoretical part of this work describes the foam from the physical aspect. There are described fourth key events involved in foam formation. Then it focuses on the beer foam – its structure, substances that influence its behavior and measurement of the foam stability. In this part there are described biosurfactants as well – their characteristics, qualities, distribution and applications. The experimental part is dedicated to the influence of ethanol, surface tension, the amount of iso- acids on foam stability in beer. There is observed the influence of biosurfactants of the foam stability and surface tension, which are added into to the beer. For the measurement of the foam stability was used the Rudin method. Liquid chromatography with DAD detector was used for the measurement the amount of the hop acids. The surface tension was determined by tensiometer. According to the results addition of ethanol changed the characteristics of the foam stability, but it’s not easy to find correlation between the increasing amount of ethanol and its stability. It was found out, that there is connection between the amount of ethanol and surface tension. On the other hand, there is not much connection between the surface tension and foam height. Within the framework of addition of biosurfactants was observed, that these foaming agents interacted the surface tension of the beer (lowering), however these agents accelerated the fall of the beer foam.