Viktória Bódai

Kinetic resolution of 1-(benzofuran-2-yl)ethanols by lipase-catalyzed enantiomer selective reactions

Abstract Kinetic resolution of racemic 1-(benzofuran-2-yl)ethanols rac - 1a – d was performed by lipase-catalyzed enantiomer selective acylation ( E ≫100) yielding (1 R )-1-acetoxy-1-(benzofuran-2-yl)ethanes ( R )- 2a – d and (1 S )-1-(benzofuran-2-yl)ethanols ( S )- 1a – d in highly enantiopure form. The degree of enantiomer selectivity for enzymatic alcoholysis/hydrolysis processes starting from racemic 1-acetoxy-1-(benzofuran-2-yl)ethane rac - 2 was also tested under various conditions including supercritical CO 2 medium. Racemization-free lipase-catalyzed ethanolysis of the (1 R )-1-acetoxy-1-(benzofuran-2-yl)ethanes ( R )- 2a – d yielded almost quantitatively the enantiopure (1 R )-1-(benzofuran-2-yl)ethanols ( R )- 1a – d .

Kinetic resolution of trans-2-acetoxycycloalkan-1-ols by lipase-catalysed enantiomerically selective acylation

Abstract Kinetic resolution of a series of racemic trans -cycloalkane-1,2-diol monoacetates rac - 2a – d was performed by enantiomerically selective transesterification with vinyl acetate catalysed by commercial and our own-prepared fungal lipases to yield diacetates ( R , R )- 3a – d and monoacetates ( S , S )- 2a – d in high enantiomeric purity. The monoacetates ( R , R )- 2a – d were also prepared from the racemic diacetates rac - 3a – d by lipase-catalysed hydrolysis.

Chemo-enzymatic preparation of hydroxymethyl ketones

A series of hydroxymethyl ketones 4a–g were obtained from the corresponding halogenomethyl ketones 2a–gvia their transformation into acetoxymethyl ketones 3a–g by 18-crown-6 catalysed substitution with NaOAc followed by Novozyme 435™ catalysed ethanolysis. This convenient chemo-enzymatic route provides a mild, heavy-metal-free alternative to the direct α-hydroxylations of methyl ketones 1a–g.

Green synthesis of gold nanoparticles by thermophilic filamentous fungi

Alternative methods, including green synthetic approaches for the preparation of various types of nanoparticles are important to maintain sustainable development. Extracellular or intracellular extracts of fungi are perfect candidates for the synthesis of metal nanoparticles due to the scalability and cost efficiency of fungal growth even on industrial scale. There are several methods and techniques that use fungi-originated fractions for synthesis of gold nanoparticles. However, there is less knowledge about the drawbacks and limitations of these techniques. Additionally, identification of components that play key roles in the synthesis is challenging. Here we show and compare the results of three different approaches for the synthesis of gold nanoparticles using either the extracellular fraction, the autolysate of the fungi or the intracellular fraction of 29 thermophilic fungi. We observed the formation of nanoparticles with different sizes (ranging between 6 nm and 40 nm) and size distributions (with standard deviations ranging between 30% and 70%) depending on the fungi strain and experimental conditions. We found by using ultracentrifugal filtration technique that the size of reducing agents is less than 3 kDa and the size of molecules that can efficiently stabilize nanoparticles is greater than 3 kDa.

Sensitivity enhancement for mycotoxin determination by optical waveguide lightmode spectroscopy using gold nanoparticles of different size and origin

Mycotoxins, present in a wide range of food and feed commodities, are toxic secondary metabolites produced by a number of different fungi. Certain mycotoxins do not readily degrade at high temperatures, therefore are resistant to food processing, and consequently are present in the human and animal food supply. Optical waveguide lightmode spectroscopy (OWLS) was applied for the detection of aflatoxin B1, in a competitive immunoassay format, to compare the analytical sensitivity achieved with an immunosensor design allowing signal enhancement by increasing the sensor surface through immobilization of gold nanoparticles (AuNPs) of different size and origin (obtained by chemical or biotechnological synthesis). The effects of AuNPs median size, the methods of sensitization and the biochemical parameters on immunosensor performace were examined. After optimization of the sensitized sensor surface, an immunosensing method was developed for the analysis of aflatoxin in paprika matrix and the results were compared with HPLC reference measurements.

Co-immobilized Whole Cells with ω-Transaminase and Ketoreductase Activities for Continuous-Flow Cascade Reactions

An improved sol–gel process involving the use of hollow silica microspheres as a supporting additive was applied for the co‐immobilization of whole cells of Escherichia coli with Chromobacterium violaceum ω‐transaminase activity and Lodderomyces elongisporus with ketoreductase activity. The co‐immobilized cells with two different biocatalytic activities could perform a cascade of reactions to convert racemic 4‐phenylbutan‐2‐amine or heptan‐2‐amine into a nearly equimolar mixture of the corresponding enantiomerically pure R amine and S alcohol even in continuous‐flow mode. The novel co‐immobilized whole‐cell system proved to be an easy‐to‐store and durable biocatalyst.