Phenylacetaldehyde can be obtained by oxidation of 2-phenylethanol with acetic acid bacteria in two-liquid-phase systems where the aldehyde is removed into the organic phase before its further conversion to acid. Two Acetobacter strains (ALEF and ALEG) were able to accumulate aldehyde when aliphatic hydrocarbons were used. A two-liquid-phase system, composed of water and isooctane (v/v, 1/1), was particularly suited for a significant accumulation of the aldehyde: Acetobacter sp. ALEG furnished 9 g/l of phenylacetaldehyde within 4 h starting from 10 g/l of alcohol and still 8 g/l were recovered after 24 h in the organic phase, whereas strain ALEF gave 3.5 g/l of aldehyde from 5.0 g/l of substrate. Acetobacter sp. ALEG also showed satisfactory long-term stability, being able to perform the transformation with 80% of the original activity after 3 days of contact with the solvent.