Table 1.

Improvement in fermentative performance by improving enzyme parameters.

Enzyme	Substrate	Km (µM)	kcat (s−1)	kcat/Km (M−1 s−1)	Performance	Source
native transaldolase (TAL) in P. stipitis for ethanol (EtOH) production from xylose (xyl)						[21]
wild-type	F6P	560 ± 50	9.5 ± 0.7	1.7 x 104	1.45 ± 0.06 g xyl consumed/L/hr 0.69 ± 0.05 g EtOH produced/L/hr
Q263R		320 ± 10	32 ± 1	9.8 x 104	1.66 ± 0.04 g xyl consumed/L/hr 0.86 ± 0.05 g EtOH produced/L/hr
L. lactis alcohol dehydrogenase (AdhA) in E. coli 1993 + IlvC-6E6 for anaerobic isobutanol production						[35]
wild-type (his6)	isobutyr-aldehyde	11,700	30	2.8x103	produced 8 g/L isobutanol
RE1: Y50F, I212T, L264V		1,700	140	8.2x104	produced 13.5 g/L isobutanol
P. stipitis xylose reductase (PsXR) in S. cerevisiae for EtOH production from 15 g/L xyl and 5 g/L glucose						[36]
wild-type	NADH	30.5 ± 0.7	6.9 ± 0.1	2.3 x 105	produced 8 g/L EtOH and 5 g/L xylitol
	NADPH	2.5 ± 0.1	10.50 ± 0.02	4.2 x 106
R276H	NADH	17 ± 2	6.8 ± 0.3	4.0 x 105	produced 11 g/L EtOH and 2.5 g/L xylitol
	NADPH	1.7 ± 0.1	0.267 ± 0.003	1.6 x 105
ketol-acid reductoisomerase (IlvC) in E. coli strain 1993 for anaerobic isobutanol production						[35]
wild-type (his6)	NADH	1080	0.3	3.0 x102	produced 1 g/L isobutanol
	NADPH	40	3.6	8.7x104
6E6: A71S, R76D, S78D, Q110V	NADH	30	2.3	7.4x104	produced 3 g/L isobutanol
	NADPH	650	0.2	4.0x102
furfural reductase in ethanologenic E. coli LY180
YqhD	furfural	9,000	n/a	n/a	deletion increases tolerance to furfural by sparing NADPH for biosynthesis	[31, 32]
	NADH	n/a	n/a	n/a
	NADPH	8	n/a	n/a
FucO	furfural	400 ± 200	n/a	n/a	overexpression increases tolerance to furfural by reducing furfural to furfuryl alcohol without depleting NADPH	[37, 38]
	NADH	2.7	n/a	n/a
	NADPH	n.d.	n.d.	n.d

n.d – no activity detected

n/a – not available