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Table 3 Application of different strategies for improving γ-PGA production

From: Microbial synthesis of poly-γ-glutamic acid: current progress, challenges, and future perspectives

Starting sources Fermentation strategies Main results Ref.
B. licheniformis NCIM 2324 Optimization via one factor at a time γ-PGA production increased from 5.27 to 26.12 g/L [89]
B. subtilis CGMCC 0833 Applying pH-shift control strategy Glutamate utilization increased from 24.3 to 29.5 g/L; γ-PGA production increased from 22.2 to 27.7 g/L [62]
B. subtilis NX-2 Using a two-stage strategy for agitation speed control The concentration of γ-PGA reached 40.5 g/L with increases of 17.7 % [90]
B. subtilis NX-2 Adding different oxygen vectors The concentration of γ-PGA reached 39.4 g/L with increase of 25.1 % [59]
B. subtilis BL53 Adding some precursors The production of γ-PGA increased to 25.2 g/L [91]
B. subtilis C10 Addition of organic acid The concentration of γ-PGA increased from 17.3 to 27.7 g/L [92]
B. licheniformis NCIM 2324 Addition of metabolic precursors The concentration of γ-PGA reached 35.75 from 26.12 g/L [81]
B. licheniformis TISTR 1010 Using different feeding strategies The γ-PGA concentration reached 27.5 g/L with increase of fivefold [83]
B. subtilis NX-2 Using co-fermentation strategy The production and productivity of γ-PGA reached 73.0 g/L and 0.81 g/L/h, respectively [50]
B. subtilis CCTCC M 2012347 Solid-state fermentation Using soybean residue and cane molasses to produce 103.5 g/kg of γ-PGA at 24 h under non-sterilized condition [93]
B. amyloliquefaciens C1 Solid-state fermentation Producing 0.0437 g γ-PGA per gram of substrates at 48 h [94]
B. subtilis GXA-28 Addition of KCl The γ-PGA yield increased from 18.36 to 25.62 g/L by 39.5 % [95]
B. licheniformis Heat stress and alkaline stress treatment The maximum γ-PGA yield reached 29.34 g/L, 185 % higher than the control [78]
B. licheniformis WX-02 Alkaline pH stress treatment The maximum γ-PGA yield reached 36.26 g/L in the 50 L bioreactor, increased by 79 % compared with the control [96]
B. subtilis NX-2 Adding hydrogen peroxide The maximum concentration of 33.9 g/L γ-PGA was obtained by adding 100 µM H2O2 to the medium after 24 h. This concentration was 20.6 % higher than that of the control [97]