P. cepacia

Lipases from C. antarctica and P. cepacia showed higher enantioselectivity in the two ionic liquids l-ethyl-3-methylimidazolium tetrafluoroborate and l-butyl-3-methylimidazolium hexafluoroborate than in THE and toluene, in the kinetic resolution of several secondary alcohols [49]. Similarly, with lipases from Pseudomonas species and Alcaligenes species, increased enantioselectivity was observed in the resolution of 1 -phenylethanol in several ionic liquids as compared to methyl tert-butyl ether [50]. Another study has demonstrated that lipase from Candida rugosa is at least 100% more selective in l-butyl-3-methylimidazolium hexafluoroborate and l-octyl-3-nonylimidazolium hexafluorophosphate than in n-hexane, in the resolution of racemic 2-chloro-propanoic acid [51]. 

An example that refers to the third method additives can be employed is described below. Markedly enhanced enantioselectivity was reported for P. cepacia lipase and subtilisin Carlsberg with chiral substrates converted to salts by treatment with numerous Bronsted-Lowry adds or bases [63]. This effect was observed in various organic solvents but not in water, where the salts apparently dissociate to regenerate... 

In contrast to oxoesters, the a-protons of thioesters are sufficiently acidic to permit continuous racemization of the substrate by base-catalyzed deprotonation at the a-carbon. Drueckhammer et al. first demonstrated the feasibility of this approach by performing DKR of a propionate thioester bearing a phenylthiogroup, which also contributes to the acidity of the a-proton (Figure 4.14) [39a]. The enzymatic hydrolysis of the thioester was coupled with a racemization catalyzed by trioctylamine. Owing to the insolubility of the substrate and base in water, they employed a biphasic system (toluene/H2O). Using P. cepacia (Amano PS-30) as the enzyme and a catalytic amount of trioctylamine, they obtained a quantitative yield of the corresponding... 

In 1992, Oda et al. reported a one-pot synthesis of optically active cyanohydrin acetates from aldehydes, which were converted to the corresponding racemic cyanohydrins through transhydrocyanation with acetone cyanohydrin, catalyzed by a a strongly basic anion-exchange resin [46]. The racemic cyanohydrins were acetylated by a lipase from P. cepacia (Amano) with isopropenyl acetate as the acyl donor. The reversible nature of the base-catalyzed transhydrocyanation enabled continuous racemization of the unreacted cyanohydrins, thereby effecting a total conversion (Figure 4.21). 

Limitations of Stmctural Studies. EXAFS is not well suited for identifying weak scatterers, (e.g. oxygen in the presence of sulfur) as illustrated by recent data for the Rieske-like site in P. cepacia phthalate oxygenase (26). This site is believed to contain... 

TCE oxidation by P. cepacia G4 might generate a lesser amount of reactive products, thus preventing marked cytotoxicity. This phenomenon has important implications for TCE bioremediation. 

In a shallow aquifer, the oxidation of TCE and other chloroalkenes was compared under conditions of phenol or methane amendments (Hopkins, Semprini McCarty, 1993). The objective was to stimulate the growth and metabolism of bacteria comparable to P. cepacia G4 and M. trichosporium OB3b, respectively. It is possible, however, that the methane-stimulated bacteria expressed particulate (membrane-bound) methane monoxygenase, which is known to oxidize TCE much more slowly than sMMO (DiSpirito et al., 1992). Under the conditions used, the phenol stimulation led to greater removal of TCE and dichloroethylenes. Ammonia addition, thought to stimulate ammonia-oxidizing bacteria that oxidize TCE (Vanelli et al., 1990), showed the lowest extent of TCE oxidation in groundwater microcosm tests (Hopkins et al., 1993). 

Groundwater P. cepacia PR123 70 20 ml groundwater in Groundwater microcosms degraded Krumme et al. 

Found persistence of P. cepacia AC1100 in microcosms with and without addition of 2,4,5-T. Measured ecological effects on soil by GEM versus nonrecombinant parent uninoculated control. Microcosms supplemented with 2,4-dichlorophenoxyacetate, glucose, or unamended. 

The asymmetric hydrolysis of (exo,exo)-7-oxabicyclo[2.2.1]heptane-2,3-dimethanol, diacetate ester (37) to the corresponding chiral monoacetate ester (38) (Fig. 12B) has been demonstrated with lipases [61]. Lipase PS-30 from P. cepacia was most effective in asymmetric hydrolysis to obtain the desired enantiomer of monoacetate ester. The reaction yield of 75 M% and e.e. of >99% were obtained when the reaction was conducted in a biphasic system with 10% toluene at 5 g/liter of the substrate. Lipase PS-30 was immobilized on Accurel PP and the immobilized enzyme was reused (5 cycles) without loss of enzyme activity, productivity, or e.e. of product (38). The reaction process was scaled up to 80 liters (400 g of substrate) and monoacetate ester (38) was isolated in 80 M% yield with 99.3% e.e. The product was isolated in 99.5% chemical purity. The chiral monoacetate ester (38) was oxidized to its corresponding aldehyde and subsequently hydrolyzed to give chiral lactol (33) (Fig. 12B). The chiral lactol (33) obtained by this enzymatic process was used in chemoenzymatic synthesis of thromboxane A2 antagonist (35). 

In an enzymatic resolution approach, chiral (+)-tra .s-diol (60) was prepared by the stereoselective acetylation of racemic diol with lipases from Candida cylindraceae and P. cepacia. Both enzymes catalyzed the acetylation of the undesired enantiomer of racemic diol to yield monoacetylated product and unreacted desired (+)-trans-diol (60). A reaction yield of 40% and an e.e. of >90% were obtained using each lipase [104],... 

Structures of the native oxidized PDR from P. cepacia at 2.0 resolution and of PDR in complex with reduced NADH at 2.7 resolution have been determined (Correll et al., 1992). The enzyme folds into three domains, consisting of residues 1 to 102, 112 to 226 and 236 to 321, which bind FMN, pyridine nucleotide, and the 2Fe-2S center, respectively (Figure 11). 

Aronoff SC, Klinger JD. In vitro activities of aztreonam, piperacillin and ticarcillin combined with amikacin against amikacin-resistant Pseudomonas aeruginosa and P. cepacia isolates from children with cystic fibrosis. Antimicrob Agents Chemother 1984 25 279-280. 

The degradation of 3-chloro-4-methlaniline by P. cepacia strain CMA1 involved ring fission by an intradiol enzyme (Stockinger et al. 1992). 

Naphthalene, phenanthrene, anthracene, and fluorene by P. cepacia strain F297 (Grifoll et al. 1995) ... 

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