Biotransformation of acetophenone and its halogen derivatives by Yarrowia lipolytica strains.

The ability of 16 strains of Yarrowia lipolytica to biotransform acetophenone and its derivatives has been studied. Thirteen of these strains were derived from a wild-type strain Y. lipolytica A-101; six had the invertase gene (SUC2) from Saccharomyces cerevisiae integrated into their genome, as well as the damaged or undamaged gene encoding orotidine-5'-phosphate decarboxylase (URA3), three had integrated the damaged URA3 gene into their genome and three were UV acetate-negative mutants, not able to growth on acetate as the sole carbon source. The other tested strains included two wild strains, A-101 and PMR-1, and an adenine auxotroph ATCC 32-338A. All strains were capable of reducing acetophenone to the R-alcohol in high enantiomeric excess (80-89 %). In all of the cultures tested, reversibility of the reduction was observed, which led to an increase in the enantiomeric excess. nantioselective reduction of the acetophenone halogen derivatives revealed that the nature and location of the halogen atom had a significant influence on the enantioselectivity of the reduction. In the culture of ATCC 32-338A, after a 3-day biotransformation of 2,4'-dibromoacetophenone the enantiopure R-alcohol was obtained at a rate of 100 % of substrate conversion. In conclusion, using these invertase-containing strains or uracyl auxotrophs provided no additional benefit in terms of biotransformation capacity over the parental strain.

Microbial transformations of 6- and 7-methoxyflavones in Aspergillus niger and Penicillium chermesinum cultures.

A detailed study of the biotransformation of 6- and 7-methoxyflavones by four fungal strains (Aspergillus niger strains MB, KB, and SBP; Penicillium chermesinum 113) was carried out. Products of demethylation and also demethylation combined with hydroxylation at C-4' were identified. The biotransformation products were stronger antioxidants than the substrates.

Enantioselective dynamic process reduction of α- and ß-tetralone and stereoinversion of resulting alcohols in a selected strain culture.

α-Tetralone and ß-tetralone were subjected to biotransformation by 14 fungal strains. Enantiomeric purity of the products depended on the reaction time. 3-Day transformation of α-tetralone in Absidia cylindrospora culture gave S-(+)-1,2,3,4-tetrahydro-1-naftol of 92 % ee, whereas longer biotransformation time resulted in decrease of ee value. 3-Day transformation of ß-tetralone by the same strain gave predominantly S-(-)-1,2,3,4-tetrahydro-2-naftol, whereas after 9 days of the reaction, the R-enantiomer with 85 % ee was isolated. Transformation of ß-tetralone by Chaetomium sp. KCh 6651 gave pure (S)-(-)-1,2,3,4-tetrahydro-2-naftol in high yield at the concentration of 1 g/l. In this process, a non-selective carbonyl reduction was observed, followed by a selective oxidation of the R-alcohol.

Didymosphaeria igniaria: a new microorganism useful for the enantioselective reduction of aryl-aliphatic ketones.

Didymosphaeria igniaria is a promising biocatalyst in asymmetric reductions of prochiral aromatic-aliphatic ketones such as acetonaphthones, acetophenones, and acetylpyridines. The organism converted the substrates mainly to (S)-alcohols. Excellent results in terms of conversion and enantioselectivity (100% yield, >99% ee) were obtained with acetonaphthones. In case of acetyl pyridines, the optical purity of the product depended on the position of the carbonyl group on the pyridine ring and followed the order 2-acetyl â‰« 4-acetyl > 3-acetyl-pyridine. Transformation of o-methoxy-acetophenone gave optically pure (S)-(-)-1-(2-methoxyphenyl)-ethanol in 95% yield. The transformation of para-methyl ketone gave (R)-alcohol (81% ee), whereas para-bromo ketone gave (S)-alcohol (98% ee). Monitoring of the biotransformation of these substrates over time led to the conclusion that for both substrates, non-selective carbonyl group reduction occurred in the first step, followed by selective oxidation of the (R)-isomer of p-bromo-phenylethanol and selective oxidation of the (S)-isomer of p-methyl-phenylethanol. D. igniaria exhibited poor enantioselectivity in the reduction of bicyclic aryl-aliphatic ketones such as 1- and 2-tetralones. Only (S)-5-methoxy-1-tetralol was obtained in optically pure (>99% ee) form.

Microbial transformation of selected flavanones as a method of increasing the antioxidant properties.

Antioxidant properties of substrates [flavanone (1), 6-hydroxy- (2), 7-hydroxy- (3), 5,7,4'-trihydroxy- (5), and 7-methoxyflavanone (4)] and products of their microbial transformations, comprising hydroxylation, O-methylation, stereospecific reduction, dehydrogenation, and C-ring cleavage of the benzo-gamma-pyrone system, were determined. Measurements of the antiradical activity (expressed as IC50 value) of both the substrates and the products led to the determination of the impact of type and location of substituents in the tested flavonoids on changes in their antioxidant activities.

Biotransformations of steroid compounds by Chaetomium sp. KCH 6651.

Biotransformations of steroid compounds: androstenedione, testosterone, progesterone, pregnenolone and DHEA using Chaetomium sp. 1 KCH 6651 strain as a biocatalyst were investigated. The microorganism proved capable of selective hydroxylation of the steroid substrates. Androstenedione was converted to 14alpha-hydroxyandrost-4-en-3,17-dione (in over 75% yield) and 6beta-hydroxyandrost-4-en-3,17-dione (in low yield), while testosterone underwent regioselective hydroxylation at 6beta position. Progesterone was transformed to a single product-6beta,14alpha-dihydroxypregnan-4-en-3,20-dione in high yield, whereas biotransformation of DHEA resulted in the formation of 7alpha-hydroxy derivative, which was subsequently converted to 7alpha-hydroxyandrost-4-en-3,17-dione.

Transformations of steroids by Beauveria bassiana.

The course of transformations of testosterone and its derivatives, including compounds with an additional C1,C2 double bond and/or a 17alpha-methyl group, a 17beta-acetyl group or without a 19-methyl group, by a Beauveria bassiana culture was investigated. The fungi promoted hydroxylation of these compounds at position 11alpha, oxidation of the 17beta-hydroxyl group, reduction of the C1,C2 or C4,C5 double bonds and degradation of the progesterone side-chain, leading to testosterone. The structure of 4-ene-3-oxo-steroids had no influence on regio- and stereochemistry of hydroxylation. In a similar manner, dehydroepiandrosterone was hydroxylated by Beauveria bassiana at position 11alpha, however, a small amount of 7alpha-hydroxylation product was also formed.

Steroids' transformations in Penicillium notatum culture.

The application of Penicillium notatum genus for biotransformations of steroids has been investigated. The reactions observed include insertion of an oxygen atom into D-ring of steroids, 15alpha-hydroxylation of 17alpha-methyl testosterone derivatives, ester bond hydrolysis, and degradation of a testosterone derivatives side chain. Microbial production of testolactones, the biologically active compounds, was also achieved using this strain in up to 98% yield.

Transformations of testosterone and related steroids in Absidia glauca culture.

In the following study, the course of transformations of testosterone and its derivatives with an additional C(1)-C(2) double bond and/or 17alpha-methyl group or without 19-methyl group in Absidia glauca culture was investigated. The fungi were observed to hydroxylate these compounds and to oxidise the 17beta-hydroxyl group. The products of 6beta, 7alpha, 7beta, 11alpha, 12beta or 15beta hydroxylation were obtained. 19-Nortestosterone was also hydroxylated at the 10beta position.The position and stereochemistry of the introduced hydroxyl group was dependent on the presence of the additional C(1)-C(2) double bond, while hydroxylation at the C-6beta was unaffected. The incubation of testosterone with Absidia glauca gave hydroxyderivatives of androstenedione: 7alpha-hydroxyandrostenedione and 6beta,11alpha-dihydroxyandrostenedione. When 1-dehydrotestosterone and 1-dehydro-17alpha-methyltestosterone were used, the products were hydroxylated at 6beta, 7beta or 15beta position while 17alpha-methyltestosterone and 19 nortestosterone products were hydroxylated at 6beta, 7alpha, 11alpha or 12beta position. Two metabolites: 6beta,11alpha-dihydroxyandrostenedione and 6beta,12beta-dihydroxy-17alpha-methyltestosterone were dihydroxylated. The presence of 17alpha-methyl group in 17alpha-methyltestosterone and 1-dehydro-17alpha-methyltestosterone did not influence the position of hydroxylation.

Transformations of testosterone and related steroids by Botrytis cinerea.

Botrytis cinerea (strain AM235) was used to investigate the transformations of testosterone and related steroids. It was found that the position and stereochemistry of the introduced hydroxyl group, as well as the yield of products, depended on the structure of the substrate. Botrytis cinerea converts the examined substrates mainly to 7 alpha-hydroxy derivatives. 1-Dehydrotestosterone was also significantly hydroxylated at a 14 alpha-position.