Continuous enhancement of iturin A production by Bacillus subtilis with a stepwise two-stage glucose feeding strategy

Table 1 Comparison of major fermentation performance index with different fermentation strategies

Fermentation strategy	Iturin A concentration at 72 h (g/L)	Maximum Iturin A conc. (g/L) & time	Maximum total cell number (CFU/mL)	Ratio of spores to total cells after 48 h	Iturin A productivity at 72 h (g/L/h)
Batch fermentation	0.57	0.57 (72 h)	1.3 × 10¹⁰	0.82–1.04	0.0079
Low feeding rate (F = 0.28 g/L/h)	0.62	0.64 (83 h)	1.7 × 10¹⁰	0.80–1.08	0.0086
Moderate feeding rate (F = 0.56 g/L/h)	0.70	0.78 (84 h)	1.4 × 10¹⁰	0.79–0.92	0.0097
High feeding rate (F = 1.12 g/L/h)	0.51	0.53 (70 h)	1.6 × 10¹⁰	0.69–1.04	0.0071
Two-stage feeding strategy (F = 0.56 → F = 0.28 g/L/h)	0.68	1.12 (110 h)	1.4 × 10¹⁰	0.80–0.86	0.0094

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