Enhancing butanol tolerance of Escherichia coli reveals hydrophobic interaction of multi-tasking chaperone SecB

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

Entry	Strategy	Maximum butanol concentration (v/v)	Function or mechanism	References
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