The newly screened Aeromonas hydrophila produces copolymer consisting of 3-hydroxybutyrate (3HB) and 3-hydroxyhexanoate (3HHx). The characteristics of cell growth and polymer accumulation were examined using various carbon sources. P(3HB-co-3HHx) was produced from lauric acid and oleic acid only. P(3HB-co-3HHx) content can be increased by limitation of phosphorus. A maximal P(3HB-co-3HHx) content of 28.8 wt% could be obtained in flask culture. By applying the optimally designed nutrient feeding strategy, cell dry weight, P(SHB-co-3HHx) content, and 3HHx fraction obtained over the course of 43 h were 95.7 g/L, 45.2 wt%, and 17 mol%, respectively, resulting in a productivity of 1.01 g polyhydroxyalkanoate (PHA)/L . h. (C) 2000 John Wiley & Sons, Inc.