Quantitative transcript analysis of the inducible expression system pSIP: comparison of the overexpression of Lactobacillus spp. β-galactosidases in Lactobacillus plantarum

Table 2 β-Galactosidase activity and transcript levels

Time (h)	Time after induction (h)	pEH9R			PCN ratio pEH9R/pEH9A	pEH9A
		Activity^a	lacLM expression level	sppKR expression level		Activity^a	lacLM expression level	sppKR expression level
6 ^b	0	1	1.00 ± 0.07	1.00 ± 0.16	1.39 ± 0.25	1	1.00 ± 0.13	1.00 ± 0.21
8	2	56.1	59.9 ± 15.6	1.88 ± 0.11	0.81 ± 0.07	2.42	17.8 ± 4.3	2.49 ± 0.04
12	6	135	55.4 ± 13.5	1.67 ± 0.39	0.79 ± 0.01	4.48	11.9 ± 1.9	2.00 ± 0.20
24	18	144	16.4 ± 2.6	-	1.34 ± 0.06	3.56	0.46 ± 0.12	-

Activity levels and transcript levels of lacLM and sppKR in strains harboring pEH9R or pEH9A are related to the respective values at the induction point (6 h into the cultivation)
The plasmid copy number (PCN) ratio is the value for the pEH9R-harboring strain divided by the value for the pEH9A-harboring strain
^a Specific activity (U/mg protein)
^b Just before induction

ISSN: 1475-2859