Efficient synthesis of L-lactic acid from glycerol by metabolically engineered Escherichia coli

Table 2 Functional characterization of constructs used in the overexpression of glycerol utilization and L-lactate synthesis enzymes

	Activity (μmol/mg protein/min)^a
Enzyme tested	LA20 (Control)^b	LA20 (Overexpressed)^c
Glycerol kinase	0.187 ± 0.005	0.669 ± 0.004
Aerobic glycerol-3-phosphate dehydrogenase	0.017 ± 0.001	0.027 ± 0.002
Glycerol dehydrogenase	0.049 ± 0.002	0.39 ± 0.02
Dihydroxyacetone kinase	0.005 ± 0.001	0.019 ± 0.002
L-Lactate dehydrogenase	0.136 ± 0.005	0.68 ± 0.06

^a All activities were measured as described in Materials and Methods and values are reported as average ± standard deviation for triplicate assays.
^b Activities measured in strain LA20 containing the blank vector.
^c Activities measured in strain LA20 containing a plasmid overexpressing the specified enzyme: i.e. pZSKLMgldA for glycerol dehydrogenase and dihydroxyacetone kinase, pZSglpKglpD for glycerol kinase and aerobic glycerol-3-phosphate dehydrogenase, and pZSldh for S. bovis L-lactate dehydrogenase.
Reported values are from 36-hour shake flask cultures.

ISSN: 1475-2859