蔬菜发酵菌种的筛选及发酵特性

为了选择适合蔬菜发酵的发酵菌种，本研究从四川泡菜老汤中分离的6 种乳酸菌Lactobacillus plantarum、Lactobacillus fermentum、Lactobacillus brevi、Lactobacillus pentosus、Leuconostoc mesenteroides、Lactobacillus lactics筛选发酵菌种。6 种乳酸菌接入亚硝酸盐的MRS培养液中，6 种乳酸菌还原亚硝酸盐的大小顺序为Lactobacilluspentosus＞Lactobacillus plantarum＞Leuconostoc mesenteroides＞Lactobacillus fermentum＞Lactobacillus lactics＞Lactobacillus brevis。以pH值降低的速率为发酵速率，Lactobacillus plantarum、Lactobacillus pentosus、Leuconostocmesenteroides这3 种发酵剂的发酵速率较其他3 种快，并且通过乳酸菌的全细胞蛋白电泳实验得出此3 种乳酸菌在甘蓝发酵过程中能够成为优势菌。从乳酸菌还原亚硝酸盐的能力、发酵速率、发酵菌种的生存能力（是否能成为优势菌）的实验结果表明Lactobacillus plantarum、Lactobacillus pentosus、Leuconostoc mesenteroides这3 种乳酸菌作为蔬菜发酵的发酵剂。通过对3 种发酵菌种发酵特性的研究可知，Leuconostoc mesenteroides较另两种生长周期短，稳定期维持时间短，很快进入衰退期。Lactobacillus plantarum菌较Lactobacillus pentosus、Leuconostoc mesenteroides耐酸，Leuconostoc mesenteroides对酸敏感。Leuconostoc mesenteroides最适生长温度为30 ℃，Lactobacillus plantarum、Lactobacillus plantarum两种菌的最适生长温度是37 ℃。15 ℃条件下Leuconostoc mesenteroides的光密度（OD600 nm）值很低，说明Leuconostoc mesenteroides较Lactobacillus plantarum、Lactobacillus pentosus对低温敏感。

Screening and Fermentation Characteristics of Strains for Fermented Vegetables

This study aimed to screen the suitable strains for vegetable fermentation from six Lactobacillus species
present in pickled vegetable, namely Lactobacillus plantarum, L. fermentum, L. brevis, L. Pentosus, L. mesenteroides and
L. lactics. During culture in an MRS medium containing nitrite, these six strains of Lactobacillus could reduce the nitrite
in the decreasing order: Lactobacillus pentosus > Lactobacillus plantarum > Leuconostoc mesenteroides > Lactobacillus
fermentum > Lactobacillus lactics > Lactobacillus brevis. The fermentation rates of L. plantarum, L. pentosus and
L. mesenteroides, as indicated by pH reduction rates, were higher than those of three other strains. Furthermore, whole-cell
protein electrophoresis indicated that L. plantarum, L. pentosus and L. mesenteroides were the dominant bacteria in cabbage
fermentation. Their applicability as starter cultures for vegetable fermentation was also confirmed based on nitrite-reducing
ability, fermentation rate and viability. Comparing their fermentation characteristics, it was found that the growth cycle
and stationary phase of Leuconostoc mesenteroides were shorter than those of the other two strains, and entered the decline
phase earlier. L. plantarum was more resistant to acids than L. pentosus and L. mesenteroides and Leuconostoc mesenteroides
was more sensitive to acids. The optimal growth temperature for Leuconostoc mesenteroides was 30 ℃ whereas the optimal
growth temperature for both L. plantarum and L. plantarum was 37 ℃. At 15 ℃, the optical density (OD600 nm) of Leuconostoc
mesenteroides was very low, indicating that it is more sensitive to low temperature than L. pentosus and L. plantarum.