Table 2 Metabolic engineering strategies to improve hydrogen yields

C. acetobutylicum

Heterologous expression of hydrogenase from C. butyricum or overexpression of native hydrogenase

1.81 or 1.80 mol/mol glucose

[89]

C. butyricum

Knockout of aad (encoding aldehyde/alcohol dehydrogenase)

1.65 mol/mol glucose

[113]

C. paraputrificum

Overexpression of native [FeFe]-hydrogenase HydA

2.4 mol/mol N-acetylglucosamine

[88]

Heterologous expression of formate dehydrogenase from C. boidinii

1.390 mol/mol glucose

[102]

C. tyrobutyricum

Knockout of ack (encoding acetate kinase)

0.024 g/g glucose

[114]

Knockout of ack (encoding acetate kinase) and pta (encoding phosphate acetyltransferase)

2.61 mol/mol glucose

[115]

E. aerogenes

Heterologous expression of hydrogenase from E. cloacae

864.02 ml/g glucose

[84]

Heterologous expression of formate dehydrogenase or FhlA (a regulator activating FHL complex) from E. coli

1.589 or 1.605 mol/mol glucose

[91]

Heterologous expression of formate dehydrogenase from C. boidinii and knockout of ldhA (encoding lactate dehydrogenase)

1.702 mol/mol glucose

[101]

Overexpression of polyphosphate kinase

1.504 mol/mol glucose

[103]

Knockout of nuoCDE (encoding NADH dehydrogenase) and overexpression of nicotinic acid phosphoribosyl transferase

2.28 mol/mol glucose

[100]

E. cloacae

Overexpression of glutathione-S-transferase

2.55 mol/mol glucose

[96]

E. coli

Overexpression of native hydrogenase 3

153 mmol/mol glucose

[80]

Engineering of the large subunit of hydrogenase 3 by directed evolution

0.84 mol/mol formate

[81]

Heterologous expression of hydrogenase from Synechocystis sp. PCC 6803

1.89 mol/mol glucose

[82]

Directed evolution of FhlA by error-prone PCR

5 μmol mg/(proteinh)

[90]

Knockout of hycA (encoding a negative regulator)

31 ml/(h OD_unit L)

[93]

Knockout of hycA and overexpression of FhlA

23.6 g/(L h)

[94]

Knockout of focA (encoding formate transporter)

0.96 mol/mol glucose

[95]

Coexpression of glucose-6-phosphate dehydrogenase and fructose-1,6-bisphosphatase

21.76 mmol/mol glucose

[98]

Knockout of uptake hydrogenases and overexpression of the FHL complex

1.3 mol/mol glucose

[107]

Knockout of ldhA and frdBC (encoding fumarate reductase)

1.82 mol/mol glucose

[110]

Knockout of two uptake hydrogenases as well as ldhA and frdAB (encoding fumarate reductase)

1.80 mol/mol glucose

[111]

Knockout of ptsG (encoding glucose transporter), ldhA and frdD (encoding fumarate reductase)

0.27 mol/mol glucose/xylose

[112]

T. aotearoense

Knockout of ldh (encoding lactate dehydrogenase)

2.71 mol/mol glucose

[99]