Rhodococcus

A very simple and elegant alternative to the use of ion-exchange columns or extraction to separate the mixture of D-amino add amide and the L-amino add has been elaborated. Addition of one equivalent of benzaldehyde (with respect to die D-amino add amide) to the enzymic hydrolysate results in the formation of a Schiff base with die D-amino add amide, which is insoluble in water and, therefore, can be easily separated. Add hydrolysis (H2SQ4, HX, HNO3, etc.) results in the formation of die D-amino add (without racemizadon). Alternatively the D-amino add amide can be hydrolysed by cell-preparations of Rhodococcus erythropolis. This biocatalyst lacks stereoselectivity. This option is very useful for amino adds which are highly soluble in die neutralised reaction mixture obtained after acid hydrolysis of the amide. 

L-Phenylalanine can be synthesised from trims-cinnamic add (Figure A8.12) catalysed by a L-phenylalanine ammonia-lyase from Rhodococcus glutinis. The commercialisation of the process was limited by the low conversion (70%), low stability of the biocatalyst and die severe inhibition exerted by trims-cinnamic add. These problems were largely overcome by researchers at Genex. The process, commercialised for a short period by Gen ex, involves a cell-free preparation of phenylalanine-ammonia-lyase activity from Rhodotorula rubra. 

Rhodococcus corallinus FERM P-4812 3p-hydroxy-23,24-dinorchol-5-ene-22-oic add Mitsubishi... 

Enantioselective transformations of several cyclopropane or oxirane-containing nitriles were studied using nitrile-transforming enzymes [78]. Microbial Rhodococcus sp. whole cells containing a nitrile hydratase/amidase system hydrolyzed a number... 

Emntioselective Biotransformations of Carboxylic Acid Derivatives 145 Rhodococcus sp... 

Both cis- and trans-chrysanthemic nitriles and amides were resolved into highly enantiopure amides and acids by Rhodococcus sp. whole cells [85]. The overall enantioselectivity of reactions of nitriles originated from the combined effects of a higher (lJ )-selective amidase and a (IJ )-selective nitrile hydratase (Figure 6.29). Chrysanthemic acids are related to constituents of pyrethrum flowers and insecticides. 

The biocatalytic differentiation of enantiotopic nitrile groups in prochiral or meso substrates has been studied by several research groups. For instance, the nitrilase-catalyzed desymmetrization of 3-hydroxyglutaronitrile [92,93] followed by an esterification provided ethyl-(Jl)-4-cyano-3-hydroxybutyrate, a useful intermediate in the synthesis of cholesterol-lowering dmg statins (Figure 6.32) [94,95]. The hydrolysis of prochiral a,a-disubstituted malononitriles by a Rhodococcus strain expressing nitrile hydratase/amidase activity resulted in the formation of (R)-a,a-disubstituted malo-namic acids (Figure 6.33) [96]. 

Figure 8.3 Reduction of ketone with alcohol dehydrogenase from Rhodococcus erythropolis using formate as a hydrogen source [4a].

Several glyculosonic acids have been identified as components of bacterial polysaccharides. D-/yxo-Hexulosonic acid, as Q -D-pyranosyl residues (23), is a component of the extracellular polysaccharide from a Rhodococcus species. The LPS from Acinetobacter calcoaceticus NCTC 10305 contains - D-g/ycero-D-/a/o-octulosonic acid (24). It is isosteric with 3-deoxy-D-mnnno-octulosonic acid (25), which is a constituent of bacterial LPS and links the polysaccharide part to the lipid A region. It seems possible that D-g/ycero-D-tfl/o-octulosonic acid replaces 3-deoxy-D-/wan o-octulosonic acid in the A. calcoaceticus LPS. 

Bacteria 293 138 Mycobacterium avium (12) Novosphingobium aromaticivorans (8) Rhodococcus RHAl (20)... 

The dehydration reaction of aldoxime to form nitriles using the resting cells of Rhodococcus sp. YH3-3 was optimized. We found that the enzyme was induced by aldoxime and catalyzed the stoichiometric synthesis of nitriles from aldoximes at pH 7.0 and 30°C. Phenylacetonitrile once synthesized from phenylacetaldoxime was hydrolyzed to phenylacetic acid, since the strain has nitrile degradation enzymes such as nitrile hydratase and amidase. We have been successful in synthesizing phenylacetonitrile and other nitriles stoichiometrically by a selective inactivation of nitrile hydratase by heating the cells at 40°C for 1 h. Various nitriles were synthesized under optimized conditions from aldoximes in good yields. 

The NHase responsible for aldoxime metabolism from the i -pyridine-3-aldoxime-degrading bacterium, Rhodococcus sp. strain YH3-3, was purified and characterized. Addition of cobalt ion was necessary for the formation of enzyme. The native enzyme had a Mr of 130000 and consisted of two subunits (a-subunit, 27 100 (3-subunit, 34500). The enzyme contained approximately 2 mol cobalt per mol enzyme. The enzyme had a wide substrate specificity it acted on aliphatic saturated and unsaturated as well as aromatic nitriles. The N-terminus of the (3-subunit showed good sequence similarities with those of other NHases. Thus, this NHase is part of the metabolic pathway for aldoximes in microorganisms. 

Sulfatase alkylsulfatase from Rhodococcus ruter DSM 44541 E = 21 with additives E = 200 ... 

Patent literature reports on the analogous resolutions of phosphinotricin using, among others, penicillin G-acylase, penicillin G-amidase, subtilisin or microorganisms such as Enterobacter aerogenes, Klebsiella oxytoca, Corynebac-terium sp., Rhodococcus rubropertinctus and others7°... 

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