MICROBIAL-METABOLISM AND BIOTRANSFORMATIONS OF STYRENE

Styrene is an important industrial chemical and it is also produced naturally, mainly by the decarboxylation of cinnamic acid. It possesses both an aromatic ring and a vinyl side-chain and so there are many possible routes for its metabolism. Mammalian liver oxidizes styrene, attacking its side-chain to give styrene oxide, followed by hydration to yield phenylethanediol. A strain of Pseudomonas putida has been reported to use the same route. Initial dioxygenase ring attack followed by meta-cleavage of the ring occurs in a strain of Rhodococcus rhodochrous, and it has been suggested that initial ring attack occurs in other organisms. Many isolates degrade styrene through phenylacetic acid, and in one of these bacteria certain of the enzymes have been shown to be plasmid-encoded. Styrene can be degraded anaerobically by both consortia and pure cultures. Bacteria are able to metabolize alpha- and beta-styrene as well as styrene dimers and tetramers, although higher oligomers of styrene are recalcitrant. Styrene-degrading organisms have been used in experimental gas filters, and chiral synthetic precursors based on styrene can be produced using microbial enzymes.