The Pseudomonas oleovorans alkane hydroxylase and xylene oxygenase from Pseudomonas putida are versatile mono-oxygenases for stereo-and regioselective oxidation of aliphatic and aromatic hydrocarbons. Pseudomonas oleovorans and alkanol dehydrogenase deficient mutants of Pseudomonas have previously been used to produce alkanols from various alkanes and optically active epoxides from alkenes. Similarly, P. putida strains have been used to produce aromatic alcohols, aromatic acids, and optically active styrene oxides. A limitation in the use of Pseudomonas strains for bioconversions is that these strains can degrade some of the products formed. To counter this problem, we have constructed fscherichia coli recombinants, which contain the alk genes from the OCT plasmid of P. oleovorans If. coli HB101 (pGEc47)I and the xylMA genes from the TOL plasmid of P. putida mt-2 [E. coli HBlOl (pGB6311, encoding alkane hydroxylase and xylene oxygenase, respectively. fscherichia coli HBlOl (pGEc47) was used t o produce octanoic acid from n-octane and f. coli HBlOl (pBG63) was put to use for the oxidation of styrene to styrene oxide in two-liquid phase biocatalysis at high cell densities. The alk+ recombinant strain E. coli HBlOl (pGEc47) was grown t o 40 g/L cell dry mass in the presence of n-octane, which was converted to octanoic acid by the alkane oxidation system, the product accumulating in the aqueous phase. The xy/+ recombinant f. coli HBlOl (pBG63) was grown to a cell density of 26 g/L cell dry mass in the presence of around 7% (v/v) n-dodecane, which contained 2% (v/v) styrene. The recombinant E. coli ( x y U converted styrene t o (S)-(+)-styrene oxide at high enantiomeric excess (94% ee) and this compound partitioned almost exclusively into the organic phase. Using these high-cell-density two-liquid-phase cultures, the products accumulated rapidly, yielding high concentrations of products (50 mM octanoic acid and 90 m M styrene oxide) in the respective phases.