Table 2.

Comparison of lactic acid fermentation with and without a neutralizing agent from several studies.

Microbial host	Strategies	Conditiona	Time (h)	Titer (g L−1)	Yield (g g−1 glucose)	Productivity (g L−1 h−1)
Pichia kudriavzevii DKA34	Deletion of PDC1 and insertion of two copies of LDH Enhanced acid-tolerance by adaptive laboratory evolution Fed-batch strategy	SN (Ca(OH)2 to pH 4.7)	33	154	0.72	4.16
		NN	42	60.1	0.78	1.43 (− 66%)b
Candida sonorensis ATCC32109-derived mutant35	Deletion of PDC1 and PDC2, and insertion of two copies of PGK1p-LDH from L. helveticus	SN (30 g L−1 CaCO3)	144	66	0.66	0.45
		NN	100	14	0.28	0.14 (− 66%)b
S. cerevisiae YIBO-7A25	Deletion of PDC1 and insertion of two copies of LDH from Bovine	SN (50 g L−1 CaCO3)	42	55.6	0.62	1.11
		NN	72	50.6	0.51	0.70 (− 37%)b
S. cerevisiae δpHδLA2-51/dP3636	Deletion of PDC1 and insertion of LDH from Leuconostoc mesenteroides	SN (20 g L−1 CaCO3)	23	52.2	0.55	2.27
		NN	52	33.9	0.29	0.65 (− 71%)b
S. cerevisiae BK0137	Insertion of LDH from L. acidophilus and introduction of xylose oxidoreductase pathway derived from Pichia stipites Enhanced lactic acid tolerance by adaptive laboratory evolution	NN	96	119	0.60	1.24
S. cerevisiae BTCC3 LA2 (this study)	Utilization of an originally robust strain Deletion of PDC1 and PDC5, and insertion of only one copy of PDC1p-LDH from Lactobacillus casei High cell density cultivation	Batch:
		SN (50 g L−1 CaCO3)	9	43.2	0.43	4.80
		NN	9	33.2	0.33	3.68 (− 23%)b
		Fed-batch:
		SN (50 g L−1 CaCO3)	18	53.7	0.33	2.98
		NN	18	39.3	0.24	2.18 (− 27%)b

^aSN semi-neutralized, NN non-neutralized.

^bThe percentage values indicate the drop in productivity when no calcium carbonate was added at the beginning of fermentation.