Table 3 Engineering strategies to improve butanol tolerance of E. coli

1

Overexpression of CRP variants

1.2% butanol

Global transcription factor, 308 genes with > 2.0-fold difference in expression level

[38, 39]

2

Overexpression of groESL

1.0% butanol

Folding both nascent and misfolded proteins

[25]

3

Overexpression of OmpC-TMT

1.5% butanol

Scavenging of intracellular and extracellular free radicals

[40]

4

Knockout of lon and proV

2.0% butanol

High expression of AcrAB–TolC pump

[19]

5

Overexpression of acrB_{I466F/M355L/S880P}

25% increase at 0.7% butanol

Promoting secretion of butanol from the cell

[15]

6

Overexpression of ATF, fabD, feoA and srpABC

2.0% butanol

Synergistic effect of artificial transcription factor, fatty acid synthesis, iron-uptaking protein FeoA, efflux pump SrpABC from Pseudomonas putida

[41]

7

Overexpression of rpoD

2.0% butanol

Global transcription factor, 197 upregulated genes and 132 downregulated genes

[20]

8

Overexpression of secB_T10A

1.8% butanol (5.3-fold improvement in T at 1.2% butanol)

Exporting nascent unfolded protein, improved binding affinity of substrate proteins

This study