Carbon dioxide fixation by Calvin-Cycle enzymes improves ethanol yield in yeast

Table 1 Physiological analysis of S. cerevisiae IMU033 expressing PRK and Rubisco and the isogenic reference strain IMU032 in anaerobic chemostat cultures, grown at a dilution rate of 0.05 h ^-1 on a synthetic medium (pH 5) supplemented with 12.5 g l ^-1 glucose and 12.5 g l ^-1 galactose as carbon sources ^#

	IMU032		IMU033
	(Reference strain)		(Expressing PRK and Rubisco)
CO₂ in inlet gas (%)	0	10	0	10
CO₂ in outlet gas (%)	0.89 ± 0.03	10.8 ± 0.0	1.02 ± 0.00	10.8 ± 0.1
Phosphoribulokinase (μmol mg protein^-1 min^-1)	0.58 ± 0.09	0.51 ± 0.12	14.4 ± 1.5	15.2 ± 1.0
Rubisco (nmol mg protein^-1 min^-1)	< 0.2*	< 0.2	4.59 ± 0.30	2.67 ± 0.28
Biomass yield on sugar (g g^-1)	0.083 ± 0.000^a	0.084 ± 0.000^b	0.093 ± 0.001^a	0.095 ± 0.000^b
Ethanol yield on sugar (mol mol^-1)	1.56 ± 0.03^c	1.56 ± 0.02^d	1.73 ± 0.02^c	1.73 ± 0.01^d
Glycerol yield on sugar (mol mol^-1)	0.14 ± 0.00^e	0.12 ± 0.00^f	0.04 ± 0.00^{e, g}	0.01 ± 0.00^{f, g}

^#Results are represented as average ± mean deviations of data from independent duplicate chemostat experiments. Data pairs labelled with the same subscripts (^a,a, ^b,b, etc.) are considered statistically different in a standard t-test (p <0.02).
*Detection limit of enzyme activity assay.

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