Izabela Stolarzewicz

Studies on the lipolytic activity of sonicated enzymes from Yarrowia lipolytica

The aim of this study was to evaluate the efficiency of sonication in releasing protein from a widespread lipase-producing yeast, Yarrowia lipolytica KKP 379, and to examine the impact of ultrasound waves generated in a horn-type sonicator on the lipolytic activity of Y. lipolytica in the hydrolysis of p-nitrophenyl laurate. In this paper, we focused on a few parameters of ultrasound cell disruption, such as the time of sonication, acoustic power, storage time of the frozen yeast biomass used in sonication and the solvent used to suspend the yeast cells which were considered as the most important part in the process of obtaining a biocatalyst from Y. lipolytica for organic synthesis. The most effective additive in protein release proved to be 2% Tween 80; other ideal parameters of the process were ultrasonic power at 150 W for 15 min and 9 weeks of frozen biomass storage time. The sonication parameters, which were the best for protein release, did not seem to be the most effective for obtaining high lipolytic activity due to denaturation as an effect of cavitation.

Carbon source impact on Yarrowia lipolytica KKP 379 lipase production

The production of lipases by microorganisms is strongly influenced by the culture conditions. The optimum culture conditions for enzyme production are strain- and species-dependent. The aim of this study was to evaluate the impact of the carbon source used in the culture medium on the profile of lipases produced by Yarrowia lipolytica KKP 379. We observed a different pattern of extracellular and cell-bound lipase production, which was the highest in the early exponential phase. The extracellular lipase activity increased in the late exponential phase due to the lower accumulation of lipase molecules in cell walls. The best carbon source for extracellular lipase production by Y. lipolytica KKP 379 was olive oil. Glucose, dodecane and olive oil had a positive effect on biomass yield. Dodecane and/or glycerol utilization in microbiological lipase production was possible, but this process could not proceed without the addition of some activators such as olive oil in the cultivation medium.

Catalytic activity of baker's yeast in ester hydrolysis

Abstract The hydrolysis of phenyl esters of alkane carboxylic acids in the presence of lyophilized Saccharomyces cerevisiae has been studied. In the case of phenyl acetate the hydrolysis obeyed Michaelis–Menten kinetics, behavior typical of esterase-catalyzed reactions. For phenyl laurate our experiments provided evidence for the growth-associated production of lipase by bakers yeast.

Synthesis and study of new liquid crystalline compounds with an epoxy group

The influence of the transformation of a terminal double bond to an epoxide group in the series of compounds containing phenyl benzoate moiety as the mesogenic rigid core is investigated. The epoxide derivatives are obtained by biotransformation methods. The double bond or epoxide ring are separated by different numbers of methylene units from the phenyl ring of benzoic acid in its methoxy or decyloxyphenyl esters. The mesogenic properties of the synthesised compounds are investigated by optical microscopy, calorimetric and X‐ray methods. In contrast to methoxyphenyl esters most of decyloxyphenyl esters showed enantiotropic liquid crystalline behaviour. The replacement of the double carbon–carbon bond by the polar and bulky epoxy group destabilises the mesophase in almost all cases.

Plant and microbial sources of antioxidants

In recent years there has been growing interest in substances with antioxidative properties, which reduce or prevent harmful effects of free radicals on living tissues, and inhibit aging processes and the development of certain diseases. The objective of this paper is to review new methods of obtaining antioxidants of plant origin and new trends in research aiming to improve their quality and profitability on an industrial scale. Among the issues discussed, there are the methods that use techniques of plant and microbial genetic engineering. A brief description of antioxidants and natural sources of their occurrence is also presented in this paper. In view of the fact that the biosynthesis of flavonoids and isoflavonoids is probably the best-known metabolic pathway of natural plant products, the review of achievements of recent years in the field of metabolic engineering was shown with the example of flavonoids. The modifications of flavonoid biosynthetic pathways were related to changes in the expression level of structural or regulatory genes, silencing of competitive genes or modifying catalytic properties of enzymes using techniques of protein engineering. The paper also presents the achievements of microorganism engineering in the field of application of fermentation processes as a source of specific flavonoid compounds, which was possible by designing the phenylpropanoid biosynthetic pathway in cells of microorganisms such as the bacterium E. coli or S. cerevisiae, bakers yeast. Both approaches can be used in the production of flavonoids attractive in terms of application.

Study on the Properties of Immobilized Biocatalysts with Lipase Activity Produced by Yarrowia lipolytica in Batch Culture

Three kinds of matrices (calcium alginate, gelatin, and PVA) were employed as supports to immobilize lipases from Y. lipolytica KKP 379 via physical adsorption. The stability of biocatalysts (free and immobilized) was evaluated by measuring the enzyme activity before and after treatment with the method based on the hydrolysis of p-nitrophenyl laurate. Two fractions of enzymes were immobilized: cell-bound (yeast biomass) and extracellular (supernatant). The yield of immobilization and catalytic properties of immobilized lipases were investigated. Satisfactory results for lipolytic activity and biocatalyst stability were obtained for cell-bound enzymes immobilized in alginate (0.38 U g–1 d.m.) and crosslinked gelatin (0.18 U g–1 d.m.). Immobilization of the supernatant was successful only on the alginate (0.026 U g–1 d.m.). After lyophilization, no significant difference was noticed between treated and untreated biocatalysts. Lyophilized catalysts were successfully immobilized in all three matrices, but the process reduced their lipolytic activity probably due to an insufficient amount of water in the reaction solution.