Table 2 Application of various strategies to improve cellular performance for ABE fermentation

Mutagenesis strategies

 C. acetobutylicum BKM19

Random mutagenesis, screening cells on fluoroacetate plates

Butanol: 15.9/17.6 g/L

Total solvent: 24.9/32.5 g/L

[195]

 C. acetobutylicum JB200

Evolution in a fibrous bed bioreactor

Butanol: 12.6/21.0 g/L

Total solvents: 19.4/32.6 g/L

[93]

 C. acetobutylicum GX01

NTG, genome shuffling and butanol exposure

Butanol: 16.3/20.1 g/L

Total solvents: 26.4/32.6 g/L

[86]

Metabolic engineering strategies

 Enhancing butanol production

  C. acetobutylicum ATCC 824

Overexpressing both pfkA and pykA genes

Butanol: 14.78/19.12 g/L

Total solvents: 21.76/28.02 g/L

[78]

  C. acetobutylicum JB200

Disrupting the cac3319 gene

Butanol: 12.6/18.2 g/L

[93]

  C. beijerinckii CC101

Overexpressing adhE2 and ctfAB

Butanol: 2.6/12.0 g/L

[223]

 Increasing butanol selectivity

  C. acetobutylicum ATCC 824

Knocking out solR

Butanol: 5.48/17.79 g/L

Butanol ratio: 55%/66%

[224]

  C. acetobutylicum EA 2018

Disrupting the acetone pathway by TargeTron technology

Butanol: 7.4/13.6 g/L

Butanol ratio: 71/82%

[43]

 Improving butanol tolerance

  C. acetobutylicum

Overexpressing HSP genes grpE and htpG

Improved butanol tolerance with increases of 25% (grpE) and 56% (htpG)

[167]

  C. acetobutylicum

Overexpressing gshAB genes from E. coli

Increased cell resistance against butanol stress (from 14.5 to 18 g/L), and aero-stress

[83]