Table 6.

Xylose-to-glucose preference ratios and percent total sugar consumed during the competitive preference assay^a

Organism	Gene	X/G preference ratio	% sugars consumed
S. cerevisiae	HXT7	0.11	75
	GAL2	0.09	68
C. intermedia	GXF1	0.10	78
	GXS1	0.51	14
D. hansenii	xylHP	0.17	58
	S. stipitis	XUT1	0.69	16
XUT3		0.11	17

^aA cofermentation assay was conducted to determine transporter preference. The X/G preference ratio is calculated by first measuring the molar consumption rates of each sugar over the same time period from a stationary-phase yeast culture and then dividing the xylose molar consumption rate by the glucose molar consumption rate. This metric approximates how many xylose molecules per glucose molecule are imported. As a measure of transporter throughput, the total sugar consumption over 24 h was measured and taken as a mass percentage of total sugars. Several cultures exhibit diauxic sugar consumption, in which glucose is consumed first, resulting in low X/G preference ratios and high percent sugars consumed.