Growth of isolated LAB strains
Growth of four isolates was examined at different temperature,
initial pH and NaCl concentration (Figs. 1e3). As shown in Fig. 1, all
strains grew rapidly at 30 C and 37 C, and reached the highest
absorbance values (OD600 ¼ 1.5e1.6) in 6 h. But they were unable to
grow at 4 C in 48 h. Generally, Leuconostoc strains are known to
grow at low temperature such as 10 C. They are the major LAB
during kimchi fermentation and kimchi is stored at 1 C to 10 C
in most cases. Three Leuconostoc strains grew quickly at 30 C and
grew slowly at 15 C, but still faster than at 45 C. In contrast, Lb.
plantarum C182 grew best at 37 C and very slowly at 15 C.
Growth of isolates at different initial pH was examined at 30 C
for 48 h (Fig. 2). All strains grew rapidly at the initial pH of 4e9 and
reached the OD600 value of 1.5e1.6 in 6 h. At the initial pH of 2.0, all
strains were unable to grow and they grew slowly at the initial pH
of 3.0.
Tolerance against NaCl was examined using MRS broth with
6.5% and 8% NaCl (w/v). Lb. plantarum C182 was more tolerant than
Leuconostoc strains (Fig. 3). In MRS broth with 6.5% and 8% NaCl,
culture of Lb. plantarum C182 reached the OD600 value of 1.4 in 24 h
and 1.2 in 48 h, respectively. It took only 6 h for Lb. plantarum C182
to reach 1.4 in MRS broth without salt. Leuconostoc strains grew
slowly and reached OD600 value of 0.8e1.2 in 48 h when grown in
MRS broth with 6.5% NaCl. All strains seem to grow well in kimchi
where the salt concentration is about 2e3% (w/v).