Model-driven intracellular redox status modulation for increasing isobutanol production in Escherichia coli

Table 2 Targets predicting for regulating redox balance to increasing isobutanol production in strain LA02

Reaction name	Reaction stoichiometry	Strategy	Special growth rate (h⁻¹)	ISB special product rate (mM/g/h)	f _PH
GAPDH	glyceraldehyde 3-phosphate + NAD⁺ + phosphate ↔ 3-Phospho-glyceroyl phosphate + H⁺ + NADH	Cofactor swap	0.0231	1.842	1.944
ALCD2x^a	acetaldehyde + H⁺ + NADH → ethanol + NAD⁺	Knock out	0.0798	0.968	1.860
ACALD^a	acetyl-CoA + H⁺ + NADH → acetaldehyde + coenzyme A + NAD⁺	Knock out	0.0876	0.717	1.118
THD2pp	NADH + NADP⁺ + H⁺(extracellular) → H⁺(intracellular) + NAD⁺ + NADPH	Over express	0.0797	0.732	1.064
GLUDy^b	2-oxoglutarate + H⁺ + NADPH + NH₄ ↔ L-glutamate + H₂O + NADP⁺	Cofactor swap/knock out	0.090/0.084	0.678/0.672	1.028/0.944
FLDR2	2 flxso + NADPH → 2 flxr + H⁺ + NADP⁺	Cofactor swap	0.0925	0.671	1.035
PGCD	3-phospho-glycerate + NAD⁺ → 3-Phosphohydroxypyruvate + H⁺ + NADH	Cofactor swap	0.095	0.651	1.001
G5SD	l-Glutamate 5-phosphate + H⁺ + NADPH → L-Glutamate 5-semialdehyde + NADP⁺ + phosphate	Knock out	0.095015	0.650	0.998
G6PDH2r	glucose 6-phosphate + NADP⁺ ↔ 6-phospho-glucono-1,5-lactone + H⁺ + NADPH	Over express	0.0941	0.651	0.990
LDH_D^c	H⁺ + NADH + pyruvate → lactate + NAD⁺	Knock out	0.005^c	1.829	0.416

The growth and isobutanol production rates of strain LA02 were respectively 0.095 h⁻¹ and 0.65 mM/g/h.
Flxso flavodoxin semi oxidized, flxr flavodoxin reduced, ISB isobutanol.
^aThe reactions ALCD2x and ACALD were two steps of ethanol production by the same enzyme alcohol dehydrogenase encoded by adhE gene.
^bThe reaction GLUDy, catalyzed by glutamate dehydrogenase consuming NADPH, could be knocked out or cofactor swapped for improving NADPH supply.
^cThe strain could not growth after LDH_D knockout with special growth rate predicted as 0.005 h⁻¹.

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