Browsing by Author "Layh, Norman"

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    Enantioselective hydrolysis of O-acetylmandelonitrile to O-acetylmandelic acid by bacterial nitrilases
    (1992) Layh, Norman; Stolz, Andreas; Förster, Siegfried; Effenberger, Franz; Knackmuss, Hans-Joachim
    Bacteria were enriched from soil samples, using benzylcyanide, α-methyl-, α-ethyl- or α-methoxybenzyl-cyanide as the sole source of nitrogen. All isolated strains belonged to the genus Pseudomonas. Resting cells of the isolates hydrolysed O-acetylmandelonitrile to O-acetylmandelic acid, O-acetylmandelic acid amide and mandelic acid. From racemic O-acetylmandelonitrile all isolates preferentially formed R(–)-acetylmandelic acid ( = d-acetylmandelic acid). The enantioselective hydrolysis of O-acetylmandelonitrile could also be demonstrated in vitro. Crude extracts did not hydrolyse O-acetylmandelic acid amide indicating an enantioselective nitrilase rather than a nitrile hydratase/amidase system.
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    Enantioselective hydrolysis of racemic naproxen nitrile and naproxen amide to S-naproxen by new bacterial isolates
    (1994) Layh, Norman; Stolz, Andreas; Böhme, Joachim; Effenberger, Franz; Knackmuss, Hans-Joachim
    Bacteria were enriched from soil samples with succinate as a carbon source and racemic naproxen nitrile [2-(6-methoxy-2-naphthyl)propionitrile] as sole source of nitrogen. Since naproxen nitrile was only poorly soluble in water media amended with different water-immiscible organic phases were used for the enrichments. With pristane (2,6,10,14-tetramethylpentadecane) as the organic phase two bacterial strains were isolated (strain C3II and strain MP50) which were identified as rhodococci. Cells of both strains converted naproxen nitrile via naproxen amide to naproxen. From racemic naproxen nitrile Rhodococcus sp. C3II formed S-naproxen amide and subsequently S-naproxen. Racemic naproxen amide was hydrolysed to S-naproxen. Rhodococcus sp. MP50 converted racemic naproxen nitrile predominantly to R-naproxen amide and racemic naproxen amide to S-naproxen. With both strains racemic naproxen amide was converted to S-naproxen with an enantiomeric excess >99% at a conversion rate up to 80% of the theoretical value. In strain C3II the enzymes which hydrolysed naproxen nitrile and naproxen amide were present only at a low constitutive level. In contrast, in Rhodococcus sp. MP50 these activities were induced when grown in the presence of various nitriles.