Improving poly-(γ-glutamic acid) production from a glutamic acid-independent strain from inulin substrate by consolidated bioprocessing

To excavate the application of Jerusalem artichoke on poly(gamma-glutamic acid) (gamma-PGA) production, a gamma-PGA producing strain Bacillus amyloliquefaciens NX-2S154 was obtained through atmospheric and room temperature plasma mutagenesis, which produced 14.83 +/- 0.31 g/L of gamma-PGA in batch fermentation with raw inulin extract. Simultaneous saccharification and fermentation (SSF) by adding commercial inulinase were further investigated for gamma-PGA fermentation. Results showed SSF could eliminate the ineffective utilization of inulin while avoiding inhibition effect of high concentration substrate, which made gamma-PGA concentration reach 18.54 +/- 0.39 g/L with the process being shortened by 17%. Finally, an immobilized column for reducing inulinase cost was introduced to gamma-PGA production. Repeated batch cultures showed the novel bioreactor exhibited higher stability and simplicity and gave average gamma-PGA concentration and productivity of 19.40 +/- 0.37 g/L and 0.27 +/- 0.008 g/L/h, respectively. This work proposes a productive method for efficient gamma-PGA production using Jerusalem artichoke feedstock.