Table 2 Optimization of lactose concentrations in different types of media

Lactose (g/L)	Media types	OD₆₀₀	Ethanol (g/L)	Yield (g ethanol/g lactose)	Conversion efficiency^a
7.2	SA^b	2.0	3.2	0.45	0.83
15.1	SA^b	2.3	6.7	0.44	0.82
24.0	SA^b	2.9	10.3	0.43	0.80
31.8	SA^b	3.6	12.0	0.38	0.71
32.0	RWP+YE^c	7.2	13.4	0.42	0.78
40.0	RWP+CSLH^d	4.0	17.5	0.44	0.82
80.0	RWP+CSLH^e	6.0	30.6	0.40	0.71
80.0^g	RWP+CSLH^f	6.0	41.0	0.38	0.70

^aConversion efficiency was calculated based on the theoretical maximal yield (0.538 ethanol/g lactose)
^bThe composition of SA medium can be seen in reference 20. It includes 19 amino acids, vitamins, and salts. Glucose was replaced by lactose
^cDiluted RWP (residual whey permeate) and 0.5 % (w/v) YE (yeast extract)
^d–fDiluted RWP (residual whey permeate) and 2.5 % (w/v) CSLH (corn steep liquor hydrolysate), prepared by condition H1
^gFed-batch was performed with initial 80 g/L lactose and the details can be found in Fig. 7

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