Gamma-aminobutyric acid (GABA) is a non-protein amino acid that is widely distributed in animals, plants, and microorganisms. GABA acts as a primary inhibitory neurotransmitter in the mammalian central nervous system, and is synthesized by the irreversible α-decarboxylation of acidic glutamate in the presence of glutamate decarboxylase. GABA is not only present in the central nervous system, but is also found throughout the body. GABA plays a major role in human health because it has numerous physiological functions and positive effects on many physiological disorders. Many microorganisms which possess glutamate decarboxylase have been reported to produce GABA from many food media containing glutamate. Among them, the major GABA-producers are lactic acid bacteria (LAB), which have been isolated from variety of fermented foods such as kimchi, cheese, and salted seafood. Some GABA-producing LAB strains have been shown a great potential in large-scale fermentation for the mass production of GABA by optimizing the medium composition and culture condition. In recent years, the development of natural GABA and GABA-rich products fermented by LAB is being intensively studied due to the potential health benefits of orally ingested GABA. This article is focused on the GABA-producing LAB species, GABA-rich products fermented by LAB, and health benefits of GABA-rich products.

The aim of this study was to develop PCR primer sets for the rapid classification of lactic acid bacteria (LAB). Published gene sequences for LAB carbohydrate metabolic enzymes were collected from the NCBI GenBank, and 45 primer sets were designed using the gene sequences. Twelve species of LAB were used as reference strains: Lactobacillus brevis, Lactobacillus farciminis, Lactobacillus fermentum, Lactobacillus hilgardii, Lactobacillus plantarum, Weissella cibaria, Weissella confusa, Weissella kimchii, Leuconostoc citreum, Leuconostoc lactis, Pediococcus acidilactici, and Pediococcus pentosaceus. PCR amplification and gel electrophoresis were performed to verify the specificities of the designed primers. The results showed that the primer set No. 1 of 5'-aacaacaaaatcaccgcaca-3' & 5'- gtcgtcaatgttgtcgatgc-3' for phosphofructokinase amplified PCR products from 5 species of heterofermenter with different molecular weight depending on the genus. Primer set No. 8 of 5'-gcgtcgccgtctcg-3' & 5'- gcctgcggcttttcg-3' produced specific PCR products from three heterofermentative lactobacilli such as L. brevis, L. fermentum, and L. hilgardii. Primer set No. 18 of 5'-gtgacggtgctgtaggttca- 3' & 5'-gcagtcgcttacgccatatt-3' was specifically reacted to homofermentative species including L. farciminis, P. acidilactici, and P. pentosaceus. Hence, the primer sets which were developed in this study could be used as a tool for the classification and differentiation of homo- and hetero fermentative species in lactic acid fermented foods, like as kimchi.

The culture supernatant of Lactobacillus casei CJNU 0588 was prepared from a culture incubated in whey broth (10%, w/v). The culture supernatant stimulated the growth of Bifidobacterium longum subsp. infantis KCTC 3127 and Lactobacillus acidophilus KCTC 3145 which are recognized as human gut beneficial bacteria, whereas inhibited that of Clostridium difficile KCTC 5009 as a gut pathogenic bacterium and Escherichia coli JM109. In co-culture test, L. casei CJNU 0588 cells slightly stimulated the growth of B. longum subsp. infantis KCTC 3127 and L. acidophilus KCTC 3145 but mildly inhibited that of C. difficile KCTC 5009 and E. coli JM109. Therefore L. casei CJNU 0588 strain might positively function to gut microbiota and can be used for gut health-promoting probiotics.

The cholesterol lowering effect of vegetables fermented by Lactobacillus plantarum HY7712 was evaluated in rats fed high fat/high cholesterol diet. SD Rats were randomly divided into three groups, then fed a normal diet (ND), a highfat high-cholesterol diet (HFCD), or HFCD and vegetables fermented by HY7712 (VFLAB) for 5 weeks, and the biomarkers in the blood, liver, and feces of rats were measured. Antioxidant status such as SOD, CAT, GSH/GSSG, and MDA was significantly deteriorated in HFCD compared with ND (p<0.01) but was improved in VFLAB to the level of ND. In addition, the level of MDA in VFLAB was significantly decreased in comparison with HFCD (p<0.05). Total cholesterol, LDLcholesterol, and atherogenic index (AI) were significantly increased in HFCD, but significantly decreased in VFLAB (p<0.05). In addition, administration of a HFCD diet increased the fecal bile acid in rats and the concentration of fecal bile acid was higher in VFLAB than in HFCD. In conclusion, the vegetables fermented by L. plantarum HY7712 improved antioxidant status and hypercholesterolemia induced by HFCD diet, which may be due to the synergic effect of lactic acid bacteria and fermented vegetables.

This study was conducted to evaluate the biopreservative potential of a bacteriocin-containing cell-free culture from Lactococcus lactis A164 on tofu. In order to increase the shelf-life of tofu, cell-free culture of A164 was added to tofu coagulant agent for coagulation process. Compared with tofu treated with distilled water, lactic acid, or cell-free culture from Lactobacillus plantarum P23, the tofu treated with a bacteriocin-containing cell-free culture from A164 could significantly suppress the number of total bacteria and extend the shelf-life of tofu. The antibacterial activity of tofu treated with cell-free culture from A164 was further evaluated by using modified agar diffusion method with Weissella paramesenteroides ATCC33313, as an indicator strain. The cell growth of the indicator strain was significantly inhibited by tofu treated with cell-free culture from A164. These results indicate that a bacteriocin-producing strain, L. lactis A164, can be used as a biopresevative for extending the shelf life of fresh-processing foods such as a tofu.

Lactic acid bacteria were cultivated from the gut of insects and analyzed. The gut samples were obtained from Anoplocnemis dallasi, Apis mellifera, Diestrammena coreana, Gonolabis marginalis, and Mycalesis gotama. 16S rRNA gene sequence analysis revealed that the culture-dependent lactic acid bacteria isolated from the insect gut samples belonged to the genera Enterococcus, Lactobacillus, Lactococcus, Leuconostoc, and Weissella. The genera Enterococcus and Lactococcus were dominant, constituting 57% and 25% of the isolated strains, respectively. The distribution of lactic acid bacteria was found to differ according to the insect species. However, because culture-dependent methods identify only a portion of lactic acid bacterial communities, the use of culture-independent methods in future studies will be required to complement the methods used in the present study.

Many traditional fermented foods contain diverse bacteria and many lactic acid bacteria (LAB) play important roles for the fermentation of foods such as many dairy foods and kimchi. Especially, Leuconostoc mesenteroides is one of major bacteria in those fermented foods and the development of this species would be expected to be critical for strain improvement as well as the industrialization. Up to now, a lot of plasmids were isolated from Leuconostocs species including Leu. mesenteroides and a number of vector systems has been developed. Many plasmid vector systems using Leuconostocs spp. employ RCR (rolling circle replication) producing single-stranded DNA intermediates or sometimes takes theta replication. These plasmids include the sequences for Pre protein, recombination specific sites such as RSA (recombination site A) and RSB (recombination site B), and single strain origins for RCR replication. This information might be helpful to elucidate the improvement of Leuconostocs spp. and moreover the development of diverse products using Leuconostocs spp.

This study is about microbiological analysis of makgeolli which was manufactured by general water or the Suanbo hot spring water. The viable cell count of lactic acid bacteria (LAB) in the makgeolli with the hot spring water was higher than that in the makgeolli with general water. At 9 d during storage at 10oC, the LAB cell count of makgeolli with general water reached 6.70 Log CFU/mL, whereas that of makgeolli with the hot spring water reached 7.30 Log CFU/mL, which indicates the hot spring water might stimulate the growth of LAB in makgeolli environment. Unlike LAB, the viable cell count of yeast in the makgeolli with general water was higher than that in the makgeolli with the hot spring water. At 21 d during storage at 10oC, the yeast cell count of makgeolli with general water reached 7.35 Log CFU/mL, whereas that of makgeolli with the hot spring water reached 6.96 Log CFU/mL. These results indicate the hot spring water can modulate the growth of LAB and yeast and positively function to the quality and shelf life of makgeolli. During the storage, the pH was not changed significantly.