title: Exploring the potential of fungal arylacetonitrilases in mandelic acid synthesis.
abstract: The application of arylacetonitrilases from filamentous fungi to the hydrolysis of high concentrations of (R,S)-mandelonitrile (100-500 mM) was demonstrated for the first time. Escherichia coli strains expressing the corresponding genes were used as whole-cell catalysts. Nitrilases from Aspergillus niger, Neurospora crassa, Nectria haematococca, and Arthroderma benhamiae (enzymes NitAn, NitNc, NitNh, and NitAb, respectively) exhibited different degrees of enantio- and chemoselectivity (amide formation). Their enantio- and chemoselectivity was increased by increasing pH (from 8 to 9-10) and adding 4-10% (v/v) toluene as the cosolvent. NitAn and NitNc were able to convert an up to 500 mM substrate in batch mode. NitAn formed a very low amount of the by-product, amide (<1% of the total product). This enzyme produced up to >70 g/L of (R)-mandelic acid (e.e. 94.5-95.6%) in batch or fed-batch mode. Its volumetric productivities were the highest in batch mode [571 ± 32 g/(L d)] and its catalyst productivities in fed-batch mode (39.9 ± 2.5 g/g of dcw). NitAb hydrolyzed both enantiomers of 100 mM (R,S)-mandelonitrile at pH 5.0 and is therefore promising for the enantioretentive transformation of (S)-mandelonitrile. Sequence analysis suggested that fungal arylacetonitrilases with similar properties (enantioselectivity, chemoselectivity) were clustered together.
authors: Laboratory of Biotransformation, Academy of Sciences of the Czech Republic, Vídeňská 1083, 142 20, Prague, Czech Republic, vesela@biomed.cas.cz.
authors: Alicja B
authors: AB
authors: Veselá
authors: Alena
authors: A
authors: Křenková
authors: Ludmila
authors: L
authors: Martínková
mesh_terms: D000619:Aminohydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D003883:Arthrodermataceae / Q000201:enzymology; D001234:Aspergillus niger / Q000201:enzymology; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008333:Mandelic Acids / Q000378:metabolism*; D055330:Nectria / Q000201:enzymology; D009492:Neurospora crassa / Q000201:enzymology; D010802:Phylogeny; D013045:Species Specificity
chemical_list: D005656:Fungal Proteins; D008333:Mandelic Acids; D000619:Aminohydrolases; C037938:mandelic acid
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