Fig. 2

Butanol production and growth curves at nitrogen replete (N+), nitrogen deplete (N−) and phosphorous deplete (P−) conditions. a Butanol accumulation after 14 days. Butanol production was abolished during nitrogen starvation if PHB synthase was present (JA01). Deletion of PHB synthase (JA02) resulted in increased butanol production during starvation. Enhanced expression of PhaJ, Ter and AdhE2 (JA04) increased butanol accumulation threefold. b Time course of butanol accumulation from strain JA02. Specific production of butanol increased up to twofold (P−) or threefold (N−). c Optical density in strain JA04 cultures. Cell densities remain constant during extended culturing in N− media. d Butanol titers and specific titers over time from strain JA04. The average specific productivities during day 4–14 of cultivation were 1.1 mg/gDCW/day (N+) and 2.7 mg/gDCW/day (N−). Error bars represent SD of biological triplicates