Biocatalysts for production of chiral epoxides

Abstract

An extensive screen for microorganisms capable of growth on olefins was carried out. Over 100 bacterial strains (mesophilic, thermophilic) were isolated in pure culture with gaseous or liquid (internal & terminal) olefins as the sole source of carbon and energy. The organisms included Aero coccus, Aeromonas,Alcaligenes, Flavobacterium, Micrococcus, Moraxella, Nocardia, Pseudomonas, Staphylococcus, Streptomyces and Vibrio spp. and a variety of Gram-negative, Gram-positive and Gram-variable rods/coccobacilli not yet identified. Given the success of isolating many different genera of alkene-utilizing bacteria, it would suggest that the ability to utilize olefin hydrocarbons is more widespread in nature than previously recognized.Initial studies involved testing a collection of strains for i) growth rate on the substrate of isolation and ii) evidence of epoxide accumulation from lower gaseous olefins. All of the 18 ethene-and propene-utilizing bacteria tested, stereospecifically formed R-1,2-epoxypropane (ee=90-96%), R -l,2-epoxybutane (ee=90-98%) and trans-(2/?,37?)-epoxybutane (ee=64-88%), as analyzed by chiral complexation glc. A particularly promising strain of Micrococcus sp. M90C was selected to demonstrate: a) Induction of epoxidation activity in carbohydrate-grown cells. b) Optimization of a biotransformation process for production of epoxyethane. c) Involvement of a specific monooxygenase in the formation of chiral epoxides. d) Stereoselectivity of epoxyalkane degradation. e) Substrate specificity toward a range of olefins.Micrococcus sp. M90C stereospecifically formed S-(+)-phenyl glycidyl ether (ee=93%) and /?-(+)-phenyl methyl sulphoxide (ee>98%), as analyzed by chiral-shift NMR and HPLC. The ability to catalyze heteroatom oxygenation as well as epoxidation of a wide range of olefins in high optical and chemical yields, demonstrates its potential as a 'general-purpose' biocatalyst for the production of optically pure oxygenated compounds.Two other promising ethene-utilizing bacteria (M26, M93 A) each catalyzed the stereospecific formation of S-(+)-phenyl glycidyl ether (ee=93%). This has attracted considerable industrial interest and is currently under investigation at ICI for commercial production of optically active./1-blockers. In addition to Micrococcus sp. M90C, the substrate specificities of 6 other organisms were studied in order to probe the active site of the enzymes involved. The pattern of reactivity for the group of 4 ethene-(M26, M90C, M93A, M186) and 2 propene-(M142, M l 56) utilizers differed from that expected with peracids, suggesting a considerable degree of enzymatic control.The nature of the substrate, however, modulated enzymatic epoxidations in Staphylcoccus sp. M97B. CONTENTS

Biocatalytic Epoxidation for Green Synthesis

“…Mahmoudian et al have tested 18 organisms that use ethene or propene as the carbon source, including Aerococcus, Alcaligenes, Micrococcus, and Staphylococcus spp., in the epoxidation of short-chain aliphatic olefins, and all of them stereospecifically produce (R)-1,2-epoxypropane (3, 90-96% ee), (R)-1,2-epoxybutane (4, 90-98% ee), and (2R, 3R)-2,3-dimethyloxirane (6, 64-88% ee) from the corresponding olefins (Scheme 13.1) [75]. Other alkene-utilizing bacteria from the genus of Nocardia, Xanthobacter, Mycobacterium, etc.…”

Stereoselective epoxidation of phenyl allyl ether by alkene-utilizing bacteria

“…Isolation, characterisation and growth characteristics of the newly isolated ethene-and propene-utilizers have been described previously (Mahmoudian 1989;Mahmoudian and Michael 1992). Cells were routinely grown at 30 ° C in 2-1 flasks containing 400 ml basal mineral-salts medium with ethene or propene (5-10%, v/v) as the sole source of carbon and energy.…”

“…These organisms included Aerococcus (M186), Alcaligenes (M101), Micrococcus (M90C) and Staphylococcus (M97B) spp. and a number of Gram-negative, Gram-positive and Gramvariable mesophilic rods/coccobacilli not yet identified (Mahmoudian and Michael 1992). The majority of ethene-and propene-grown cultures (14 organisms) accumulated phenyl glycidyl ether (0.4-1.7 mM) as the sole oxidation product from phenyl allyl ether with specific production rates (non-optimized) in the range 69-323 ixmolh -1 g-1 dry weight.…”

“…We have previously reported on the isolation of many different genera of ethene-and propene-utilizing bacteria that can accumulate epoxyalkanes as the sole oxidation product from internal, terminal, cyclic and aryl-substituted olefins in good chemical yields (Mahmoudian and Michael 1992). In view of the biological importance of beta blockers, the catalytic activity of these newly isolated bacteria for stereoselective epoxidation of phenyl allyl ether is described in the present paper.…”

Biocatalysis as an alternative for the production of chiral epoxides: A comparative review

“…For example, the strain of Aerococcus sp. M186 was reported to catalyze the transformation of propene and 1-butene into the (R)-oxides with 94% ee [105]. Furstoss and co-worker reported that a strain of the fungi Aspergillus niger could diastereoselectively transform (S)-sulcatol derivatives into a single enantiomer of (2S, 5S)-oxides (Scheme 8) [106].…”