Two-stage oxygen supply strategy for enhanced lipase production by Bacillus subtilis based on metabolic flux analysis

Lipase production by Bacillus subtilis CICC20034 was assessed by metabolic flux distribution analysis. Lipase production was tested under various oxygen supply conditions in a synthetic medium to obtain the optimal oxygen supply profile. Based on the metabolic flux analysis, a two-stage oxygen supply strategy (TOS) that maintained high oxygen supply conditions during early fermentation phase, and then step-wisely reduced aeration to keep a stable, smooth, and adequate changing dissolved oxygen (DO) level profile throughout the production phases was carried out. With the proposed control strategy, the final lipase activity in batch fermentation significantly increased and reached a high level at 0.56 U/ml, corresponding to a 51% increase. The relevant metabolic flux analysis verified the effectiveness of the proposed control strategy. By applying TOS in composite medium, the final lipase activity reached 5.0 U/ml.

► A detailed network model for Bacillus subtilis metabolism was constructed. ► Metabolic flux analysis (MFA) was used to investigate lipase production. ► Lipase production needs: high flux of tributyrin, TCA, and ATP; less biomass flux. ► TOS strategy was carried out with a 51% increase of lipase production based on MFA.