Table 2.

Fermentation of lactose to ethanol by recombinant S. cerevisiae strains

Characteristics of the strain	Cultivation conditions	Ethanol productivity (g·L·h−1)	Ethanol produced (g·L−1)	Ethanol yield (%)a	Lactose consumed (%)b	Reference
Autolytic cells expressing E. coli lacZ	Shake-flasks; Yeast Nitrogen Base/Lactose (2–6%)	0.1–0.2	5–18	73–84	>97	49
	Batch/Fed-batch; YP/Lactose (6%) + whey	1.0	9	60–70	100	52
Expression of K. lactis LAC4 and LAC12	Batch; Synthetic lactose (2.2%) medium	0.3	4	34	100	55
	Continuous; Semi-synthetic lactose (5%) medium	10–11	20	70–80	>94	58
	Batch; Cheese whey permeate (10% lactose)	1.8	53	>98	100	63
	Continuous; Cheese whey permeate (5% lactose)	9–10	20	70–80	>98	63
	Batch; Whey powder solution (15% lactose)	0.46	55	70	>98	66
	Batch; Synthetic lactose (15%) medium	1.5–2.0	63	78–84	>98	68
Secretion of A. niger β-galactosidase	Anaerobic shake-flasks; Whey permeate (10% lactose)	0.14–0.6	9.7	86	21	76
	Aerobic bioreactor; Synthetic lactose (10%) medium	0.6	30	58	97	76
	Batch; Semi-synthetic lactose (5%) medium	1.0	25	>80	>90	78
	Continuous; Semi-synthetic lactose (5%) medium	9.0	20	74–83	>90	81
	Continuous; Semi-synthetic lactose (10%) medium	3.4–7.0	32–48	70–90	>75	81

^aPercentage of the theoretical yield, which is 0.538 g of ethanol produced per g of lactose consumed (i.e., 4 mol of ethanol produced per mol of lactose consumed).

^bPercentage of the initial lactose that was consumed during fermentation.