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The Arthrobacter sp. is able to grow with (+)-, (−)-1-phenylethanol or the racemic mixture as sole source of carbon. Growth is most rapid with the (−)-isomer, doubling time 12 h. Enzymes of the already established pathway for acetophenone oxidation are also induced by growth with 1-phenylethanol and in addition an induced 1-phenylethanol dehydrogenase that requires NAD as electron acceptor is formed.

The 1-phenylethanol dehydrogenase is active with both 1-phenylethanol isomers but shows a marked preference for the (−)-isomer. Relative activity towards the two isomers is mirrored in the rates of growth with the two isomers and the oxidative capabilities of induced cells.

The metabolism of the isomers of 1-phenylethanol by the Arthrobacter sp. is integrated into the established pathway for acetophenone oxidation.

The pathway of acetophenone metabolism by Nocardia T5 shows no significant differences from that already established for metabolism of the compound by the Arthrobacter sp. The same spectrum of induced enzymes is formed and the evidence suggests that catechol oxidation again proceeds by ‘ortho’ fission and the β-oxoadipate pathway, the formation of even transient amounts of cis, cis-hydroxy muconic semialdehyde has never been observed.

In contrast the metabolism of the isomers of 1-phenylethanol by Nocardia T5 is achieved by a quite different pathway. The side chain is retained without modification during hydroxylation to yield 3-(1′-hydroxyethyl)catechol. Ring cleavage, by ‘meta fission’ yields 2,7-dihydroxy-6-oxoocta-2,4-dienoate the further fragmentation of which yields lactate and equimolar amounts of pyruvate and acetaldehyde.

Growth rates are identical, irrespective of which isomer of 1-phenylethanol is used as carbon source and the enzymes that convert 1-phenylethanol to vinyl pyruvate and lactate appear to display no specificity for that chiral centre.