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 aim of this diploma thesis was study of the isolation of polyhydroxyalkanoates using a commercial surfactant and selected biosurfactants, which were sophorolipids, coconut soap, lecithin, lauryl glucoside, coco glucoside and cocamidopropyl betaine. PHA was isolated from Schlegelella thermodepolymerans DSM 15344, where the amount of NaCl in the production medium was first optimized. The molecular weight of the isolated polymer was analyzed by SEC-MALS. The largest structural changes were recorded for coconut soap. Possible impurities in the isolated polymer were analyzed by infrared spectrometry (ATR-FTIR). The least protein contamination of the polymer was recorded with coconut soap. From the above biosurfactants, coconut soap, lauryl glucoside and coco glucoside were selected, because the highest purity of PHA was obtained. However, coconut soap had the greatest potential. The isolation temperature and surfactant concentration were optimized for selected biosurfactants. The best results were obtained at 90 °C and a concentration of 5 g/L. Furthermore, the versatility of the isolation method was tested using selected biosurfactants on various thermophilic microorganisms, which were Chelatococcus composti DSM 101465, Schlegelella thermodepolymerans DSM 15264, Tepidimonas taiwanensis LMG 22826 and Aneurinibacillus thermoaerophilus H1.

Lipases are enzymes catalyzing primarily the hydrolytic cleavage of triacylglycerol bonds. The production of lipolytic enzymes is known in many microorganisms, especially those who are able to utilize a fatty carbon substrate. Some genera of carotenogenic yeasts are characterized by this ability. Carotenogenic yeasts are characterized primarily by the formation of intracellular carotenoids, lipids and lipid-soluble substances. In addition to these metabolites, they may also produce some biosurfactants. This work deals with the production of extracellular lipolytic enzymes and biosurfactants by carotenogenic yeasts Rhodotorula glutinis, Cystofilobasidium macerans, Rhodotorula mucilaginosa and Sporidiobolus pararoseus cultivated mainly on animal waste fat at various C/N ratios (13, 25, 50, 100). Lipase activity was detected in all strains studied. Enzyme activities were measured by spectrophotometric method. Lipase induction has also been observed during cell growth, where several peaks of lipase activity have been reported, suggesting cell-associated lipase and lipase secreted into the environment. Lipase activities have also been found in cultures on glucose and glycerol carbon substrates. Further, the molecular characterization of lipolytic enzymes was performed using polyacrylamide gel electrophoresis. The formation of biosurfactants is to some extent formed by all strains. In particular, the biosurfactants of C. macerans and S. pararoseus yeast have emulsifying and solubilizing properties. Simultaneously with the production of lipase and biosurfactants, the production of characteristic high value added intracellular metabolites in S. pararoseus and R. mucilaginosa was evaluated too.

This diploma thesis deals with the microbial production of biosurfactants of selected bacterial strains. In order to test the biosurfactant production ability, screening methods were chosen to be able to review the potential of the selected strains to produce biosurfactants. With the scope of the work, 11 bacterial strains, which are used as polyhydroxyalkanoate (PHA) producers, have been tested. The ability to produce biosurfactants was tested in all strains both in complex inoculation and mineral production media. The presence of biosurfactants in Pseudomonas putida was detected on the basis of the results obtained after cultivation in inoculation and production media. The bacteria Pseudomonas fulva was put under more deep study to support their production by cultivation in different types of production media supplemented by different sources of carbon and nitrogen, and the effect of cultivation time was tested as well. Biosurfactants produced by these bacteria were subsequently identified by Fourier transform infrared spectroscopy (FTIR) on the basis of which the substances were identified as rhamnolipids. According to thin-layer chromatography result (TLC), Pseudomonas putida produces a mixture of mono- and dirhamnolipids, with monorhamnolipids being more dominant in our samples.

This diploma thesis deals with selected thermophilic representatives of genera Geobacillus, Saccharococcus and Bacillus, taking screening of its biotechnological potential into account. Bacteria from the first two genera came from Czech and German collection of microorganisms, while bacteria of genus Bacillus were natural isolates. Researched strains were examined from a viewpoint of carbon source utilization and furthermore, production of biosurfactants, extracellular hydrolytic enzymes (protease, amylase, lipase, cellulase, xylanase), organic acids, antimicrobial agents and microbial plastics – polyhydroxyalkanoates was also tested. Bacteria S. thermophilus, G. uzenensis and G. zalihae evinced a substantial ability of biosurfactant production. Strains G. jurassicus, G. uzenensis, G. gargensis and G. lituanicus were capable of intensive production of all tested, technologically significant enzymes. Highest antimicrobial effects were reached with bacteria G. stearothermophilus and G. thermocatenulatus. Largest production of acetic acid was achieved with G. jurassicus and lactic acid with G. thermodenitrificans. Ability to produce polyhydroxyalkanoates was proved at genotype level by some cultures only, however at fenotype level, response was negative. On the contrary, bacteria genus Bacillus were able to produce polyhydroxyalkanoates, although in small amounts under given circumstances. With remaining researched metabolites, production ability was considerably lower, compared to genera Geobacillus and Saccharococcus.

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.