Figure 4.

Time course of cell dry weight (CDW), P4HB content and P4HB concentration during a pulse feeding fed-batch culture of E . coli JM109 (pKSSE5.3). Glycerol and 4-hydroxybutyric acid were used as carbon source and precursor, respectively. Cultivation was conducted at 32°C in a 1 L bioreactor with an initial volume of 600 mL of modified M9 medium plus 20 g L⁻¹ glycerol, 6 g L⁻¹ Na-4HB, 2 g L⁻¹ acetic acid, 0.5 g L⁻¹ NZ-amines, 0.015 g L⁻¹ thiamine and 100 mg L⁻¹ ampicillin. Feeding solution was added to the bioreactor when glycerol in the medium was close to depletion, indicated by pO₂ signal. Arrow #1, feeding of 12.5 g L⁻¹ glycerol + 2.5 g L⁻¹ Na-4HB + 1.1 g L⁻¹ acetate at 30 h; Arrow #2, feeding of 25.0 g L⁻¹ glycerol + 2.1 g L⁻¹ acetate at 39 h; Arrow #3, feeding of 2.5 g L⁻¹ Na-4HB at 41 h; Arrow #4, feeding of 25.0 g L⁻¹ glycerol + 2.1 g L⁻¹ acetate + 2.5 g L⁻¹ Na-4HB at 44 h; Arrow #5, feeding of 25.0 g L⁻¹ glycerol + 2.1 g L⁻¹ acetate + 6 g L⁻¹ Na-4HB at 49.5 h. The data are the average numbers of duplicates.