Lactate production yield from engineered yeasts is dependent from the host background, the lactate dehydrogenase source and the lactate export

Table 2 Lactate and ethanol productions from different S. cerevisiae hosts transformed with different Ldh(s).

	plasmid	LDH	Lactate	EtOH	Yield	LDH activity	LDH Km
Strains		(source)	mg l^-1	mg l^-1	g g^-1	U mg^-1	mM
W303-1A	pB1	B. taurus	20	6430	0,0010	0,4	1,00 [19]
CEN.PK	pB1	B. taurus	140	6340	0,0070	0,5	1,00
GRF18U	pB1	B. taurus	801	5750	0,0401	0,6	1,00
MB11	pLC5	L. casei	200	6110	0,0100	Nd	10,00 [19]
GRF18U	pB1; pB2	B. taurus	950	5730	0,0475	0,7	1,00
GRF18U	pB1; pB2; pB3	B. taurus	1100	5648	0,0550	0,8	1,00
GRF18U	pBST2	B. stearotherm.	128	6310	0,0064	0,6	0,03 [19]
GRF18U	pBME2	B. megaterium	1371	5672	0,0686	0,7	Nd
GRF18U	pLC5	L. casei	4160	4270	0,2080	5,5	10,00
GRF18U	p022TLP	L. plantarum	6150	3730	0,3075	3,2	1,50 (this study)

All the indicated recombinant yeast strains, together with the respective control here not reported, have been grown in shake-flasks on 2% (w/v) glucose-YNB based media till stationary phase, reached after about 30 hours after the inoculum. Cultures were independently repeated, after the screening of independent transformants, (at least) three times, rising to comparable results. In the table one fermentation per each set of experiment is reported, being the independent kinetics reproducible among themselves.
Lactate and ethanol production (mg l^-1, columns 4 and 5, respectively) correspond to the highest measured production levels.
The Yield value (column 6) represents the grams of lactate produced per gram of glucose consumed (max theoretical yield = 1).
Ldh activity (column 7) has been determined at the highest lactate production level.
Km values against NADH are comprised between 0.001 and 0.0045 mM [19].
Km apparent value of mitocondrial pyruvate transporter is 0,3 mM [44]
Nd: not determined.

ISSN: 1475-2859