Metabolic engineering of Escherichia coli for the production of butyric acid at high titer and productivity

Table 1 Comparison of fermentation characteristics of butyrate-producing E. coli

Pathway^a	Medium^b	Batch/fed-batch	Titer (g l⁻¹)	Yield (g g⁻¹)^c	Productivity^d	Comment	References
Thioesterase	TB	Batch	9.7	–	–		[25]
Thioesterase	Modified TB	Batch	4.4	0.49	0.18		[26]
Thioesterase	Minimal + YE	Batch Fed-batch	7.6 12.3	– 0.31	– 0.23	Aerated Aerated	[22]
Thioesterase	TB	Batch Fed-batch	4.3 7.20	0.43 –	– –		[20]
PTB/BUK; BCD	Minimal	Batch	0.3	–	–		[19]
CoA transferase	Modified TB	Batch Fed-batch	6.8 10.0	– –	– –	+ acetate	[23]
FA pathway + CoA transferase	LB	Batch	1.0	–	–		[24]
FA pathway + thioesterase	Minimal Minimal	Batch Fed-Batch	0.8 4.6	0.11 –	– –	Aerated Aerated	[21]
PTB/BUK^e	Minimal + YE	Batch	33.1 ± 0.3	0.37 ± 0.01	0.89 ± 0.07		This study

–, Data not available
^aExcept for the FA (fatty acid) pathway, all other butyrate pathways utilized the basic Clostridium pathway with Ter substituting for BCD complex, unless stated otherwise, to butyryl-CoA followed by the indicated enzyme(s) for the conversion of butyryl-CoA to butyrate (Fig. 1). PTB, phosphotransbutyrylase; BUK, butyrate kinase; BCD, butyryl-CoA dehydrogenase complex
^bTB, terrific broth; Minimal, mineral salt medium; YE, yeast extract; LB, Luria broth
^cYield—g butyrate.(g sugar consumed)⁻¹
^dProductivity—volumetric productivity is expressed as g l⁻¹ h⁻¹ and the values reported from this study are average with standard deviation over 24 h from three independent experiments
^eValues from this study are from glucose- or xylose-mineral salt medium with yeast extract (5 g l⁻¹) and are the average and standard deviation from three independent experiments. See text for details

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