To enhance poly(γ-glutamic acid) (PGA) production, a novel aerobic plant fibrous-bed bioreactor (APFB) was constructed for immobilized fermentation. Based on the analysis of the kinetics of immobilized-cell fermentation using the APFB and conventional free-cell fermentation, immobilized-cell fermentation exhibited more efficient PGA production. Furthermore, repeated fed-batch cultures for PGA production were conducted to evaluate the stability of the APFB system. Average final PGA concentration and productivity of 71.21±0.83g/L and 1.246±0.008g/L/h were respectively achieved by cells immobilized in bagasse during APFB, which was reused eight times over a period of 457±18h. Analysis of the membrane phospholipids and the key enzyme activities indicated that APFB-adapted cells had better productivity than original cells. Thus, this study demonstrated the significant potential of the APFB culture system in future industrial applications.
Keywords: Aerobic plant fibrous-bed bioreactor; Bacillus subtilis NX-2; Cell membrane permeability; Poly(γ-glutamic acid); Repeated fed-batch fermentation.
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