Time-dependent dosing of Fe²⁺ for improved lipopeptide production by marine Bacillus megaterium

Abstract

Background: Lipopeptide production is strongly influenced by trace metals. The availability of free Fe²⁺ in the media throughout the process of fermentation was found to be very critical. Since free Fe²⁺was reported to be sequestered by the lipopeptide as it was produced, intermittent feeding of Fe²⁺was strategized and optimized for enhanced lipopeptide production by marine Bacillus megaterium in Glucose Mineral Salts Medium (GMSM). Results: Studies with the single‐dose Fe²⁺ (0.48 mmol L⁻¹) supplementation after 8 h of fermentation resulted in lipopeptide concentration of 3.3 ± 0.1 g L⁻¹. Lipopeptide production was further enhanced to 4.2 ± 0.15 g L⁻¹ by adopting a multi‐dose Fe²⁺ feeding strategy. The maximum product yield (Y_P/S) of 0.24 ± 0.02 g g⁻¹ with specific product formation rate (q_p) of 0.124 ± 0.01 g g⁻¹ h⁻¹ was achieved when 0.48 mmol L⁻¹ Fe²⁺ was fed intermittently at different times as per the designed strategy. Conclusion: Lipopeptide concentration was improved 4.7‐fold by single‐dosing and 5.8‐fold by multiple dosing of Fe²⁺ when compared with GMSM without Fe²⁺ supplementation.