An alcohol utilizing Alcaligenes eutrophus NCIMB 12080 produced a copolymer, poly(hydroxybutyrate-valerate) (PHBV), in a computer-controlled 7-L fed-batch fermenter when the alcohol feed contained pentanol. Pentanol as a sole carbon source was not efficient either for cell growth or for PHBV production. To achieve better cell growth and polymer production, two kinds of alcohol switch experiments were performed. The first was initial cell growth On a mixture of 50% ethanol (0.25 g/L) plus 50%. pentanol (0.25 g/L) and a subsequent switch to 100% pentanol(0.5 g/L). After the alcohol switch, PHBV with 99 mol % hydroxyvalerate was produced for 7-11 h. Afterward, the hydroxybutyrate (HB) composition increased and the hydroxyvalerate (HV) mol % decreased to 63.1 mol %. The total cell mass was 5.4 g/L. The second alcohol switch was from 100% ethanol (0.5 g/L) to a mixture of 80% ethanol (0.4 g/L) plus 20% pentanol (0.1 g/L). A large amount of copolymer (47 g/L) was produced with a high polymer yield (0.64 g of polymer/g of alcohol), but the HV mol % did not exceed 13.5%. Residual biomass was 8.0 g/L.