Genome sequences and functional analysis of Levilactobacillus brevis LSF9-1 and Pediococcus acidilactici LSF1-1 from fermented fish cake (Som-fak) with gamma-aminobutyric acid (GABA) production

Gamma-aminobutyric acid (GABA) is a crucial inhibitory neurotransmitter in the sympathetic nervous system that exerts regulatory effects on the blood, immune, and nervous systems. GABA production in som-fak, a traditional fermented fish of Thailand, has been attributed to the activity of lactic acid bacteria (LAB). The present study aims to characterize the LAB isolates and compare the genomes and GABA synthesis genes of selected isolates capable of GABA production. Thirteen isolates demonstrating GABA synthesis capability were identified based on their phenotypic and genotypic characteristics. Seven isolates (group I: LSF3-3, LSF8-3, LSF9-1, LSF9-3, LSF9-6, LSF9-7, and LSF10-14) were identified as Levilactobacillus brevis with 99.78-100% similarity. LSF2-1, LSF3-2, LSF5-4, and LSF6-5 (group II) were identified as Lactiplantibacillus pentosus with 99.86-100% similarity. Strain LSF1-1 (group III) was identified as Pediococcus acidilactici (99.47%), and LSF10-4 (group IV) was identified as Pediococcus pentosaceus with 99.93% similarity. The GABA production of isolates ranged from 0.087 to 16.935 g/L. The maximum production of 16.935 g/L from 3% monosodium glutamate was obtained from strain LSF9-1. Gene and genome analysis revealed that L. brevis LSF9-1 has multiple gad genes in the genome, such as gadB1, gadB2, gadC1, and gadC2, making it the potential strain for GABA production. Additionally, the genome analysis of P. acidilactici LSF1-1 consists of gadA, gadB, and gadC, which respond to controlling GABA production and export. Furthermore, strain LSF1-1 was considered safe, containing no virulence factors. Thus, Levilactobacillus brevis LSF9-1 and Pediococcus acidilactici LSF1-1 have the potential for GABA production and probiotic use in future studies.

Levilactobacillus humaensis sp. nov. and Lapidilactobacillus luobeiensis sp. nov., isolated from traditional Chinese pickle

Two Gram-stain-positive bacterial strains, designated 213-9(3)^T and 30-1(2)^T, were isolated from traditional Chinese pickle, and were characterized using a polyphasic taxonomic approach. Results of 16S rRNA gene sequence analysis indicated that strain 213-9(3)^T was most closely related to Levilactobacillus paucivorans TMW 1.1424^T, Levilactobacillus huananensis 151-2B^T and Levilactobacillus lindianensis 220-4^T, having 99.7-99.9 % 16S rRNA gene sequence similarities; strain 30-1(2)^T was most closely related to Lapidilactobacillus achengensis 247-4^T, with 99.4 % 16S rRNA gene sequence similarity. Strain 213-9(3)^T shared the highest pheS (93.9 %), rpoA (99.3 %) and concatenated pheS and rpoA (97.5 %) sequence similarities to L. paucivorans TMW 1.1424^T. Strain 30-1(2)^T had the highest pheS (82.4 %), rpoA (95.5 %) and concatenated pheS and rpoA (91.2 %) sequence similarities to L. achengensis 247-4^T. The phylogenetic relationships based on concatenated pheS and rpoA sequences and whole genome sequences were identical to those based on 16S rRNA gene sequences. Strain 213-9(3)^T exhibited the highest average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values (92.7 and 48.8 %, respectively) to L. paucivorans DSM 22467^T. Strain 30-1(2)^T had the highest ANI (84.4 %) and dDDH (32.8 %) values with L. achengensis 247-4^T. Acid production from d-galactose, d-glucose, d-mannose, N-acetyl-β-glucosaminidase, arbutin, salicin, cellobiose, maltose, gentiobiose, d-tagatose and gluconate, hydrolysis of aesculin, and activity of cystine arylamidase could differentiate strain 213-9(3)^T from L. paucivorans DSM 22467^T. Acid production from l-arabinose, d-ribose, d-xylose and d-galactose, and activity of alkaline phosphatase, esterase (C4), α-mannosidase and α-fucosidase could differentiate strain 30-1(2)^T from L. achengensis 247-4^T. Based upon the data obtained in the present study, two novel species, Levilactobacillus humaensis sp. nov. and Lapidilactobacillus luobeiensis sp. nov., are proposed and the type strains are 213-9(3)^T (=CCM 9241^T=CCTCC AB 2022115^T=JCM 35554^T) and 30-1(2)^T (=CCM 9240^T=CCTCC AB 2022114^T=JCM 35553^T), respectively.

Probiotic Properties and Optimization of Gamma-Aminobutyric Acid Production by Lactiplantibacillus plantarum FBT215

Gamma-aminobutyric acid (GABA) improves various physiological illnesses, including diabetes, hypertension, depression, memory lapse, and insomnia in humans. Therefore, interest in the commercial production of GABA is steadily increasing. Lactic acid bacteria (LAB) have widely been reported as a GABA producer and are safe for human consumption. In this study, GABA-producing LAB were preliminarily identified and quantified via GABase assay. The acid and bile tolerance of the L. plantarum FBT215 strain were evaluated. The one-factor-at-a-time (OFAT) strategy was applied to determine the optimal conditions for GABA production using HPLC. Response surface methodology (RSM) with Box-Behnken design was used to predict the optimum GABA production. The strain FBT215 was shown to be acid and bile tolerant. The optimization of GABA production via the OFAT strategy resulted in an average GABA concentration of 1688.65 ± 14.29 μg/ml, while it was 1812.16 ± 23.16 μg/ml when RSM was applied. In conclusion, this study provides the optimum culture conditions for GABA production by the strain FBT215 and indicates that L. plantarum FBT215 is potentially promising for commercial functional probiotics with health claims.

Microbial characterization of the Japanese traditional pickle senmaizuke produced by two different manufacturing processes

Senmaizuke, a traditional turnip pickle, prepared in Kyoto, Japan, is produced via two types of manufacturing processes: with and without vinegar for fermentation. The aim of this study was to reveal the microbial community and growth behavior in the products and manufacturing processes of two types of senmaizuke. Microbial growth analysis of commercial senmaizuke products showed that both types harbored 102-108 colony forming units (CFU)/g of lactic acid bacteria (LAB) and 102-104 of yeast. The fermented-type products showed successive growth of LAB during the pickling and ripening processes, whereas LAB in vinegar-type products showed growth only at the preliminary pickling step before vinegar addition; however, the bacteria were viable at the ripening step. LAB in the vinegar-type products showed growth when the pH of the pickle was neutralized, indicating that acidification via vinegar retards LAB growth. Metagenomic sequencing showed that the fermented-type products harbored Lactobacillus, Leuconostoc, and other halophilic and psychrophilic bacteria, with a higher bacterial diversity than in the vinegar-type products. In the vinegar-type products, Lactobacillus, Leuconostoc, or both were predominant. Culture tests using LAB isolates and turnip medium suggested that a change in the dominance of Leuconostoc to Lactobacillus members observed in the fermented-type products during pickling and ripening processes was attributed to the low pH sensitivity of Leuconostoc as well as a relatively long lag phase of growth for adapting to the pickling environment. The findings of this study will be useful for the appropriate quality control and assurance procedure of senmaizuke.

Genome analysis and optimization of γ-aminobutyric acid (GABA) production by lactic acid bacteria from plant materials

Gamma-aminobutyric acid (GABA) plays a key role as an inhibitory neurotransmitter in the mammalian sympathetic nervous system and has other health benefits. Molecular characterization, genome analysis, and optimization were investigated to improve GABA production of a selected strain of lactic acid bacteria. Eleven isolates from plant materials were screened for GABA productivity and were identified based on phenotypic and genotypic characteristics. The most potent strain was chosen for genome analysis and GABA production optimization using the response surface methodology (RSM). Each of the two strains was closely related to Lactobacillus plantarum, Lactobacillus brevis, Weissella cibaria, Leuconostoc pseudomesenteroides while each strain was similar to Lactobacillus pentosus, Enterococcus, and Leuconostoc mesenteroides. They produced GABA ranging from 0.036 ± 0.000 to 17.315 ± 0.171 g/L at 72 h-cultivation. Among them, the most potent strain, SL9-6, showed the highest GABA production (17.315 g/L) when cultivated with 10% (v/v) inoculum for 48 h. The draft genome sequence of strain SL9-6 exhibited 96.90% average nucleotide identity value and 74.50% digital DNA-DNA hybridization to Lactobacillus brevis NCTC 13768^T. This strain contained a glutamate decarboxylase gene system (gadA, gadB and gadC). Optimal culture conditions were determined as 40.00 g/L glucose, 49.90 g/L monosodium glutamate, pH 5.94, and 31.10°C by RSM, giving maximum GABA production of 32.48 g/L. Results from RSM also indicated that monosodium glutamate concentration, pH, and temperature were significant variables. GABA production significantly improved here could promise further application of strain SL9-6.

Characterization and comparative genomic analysis of gamma-aminobutyric acid (GABA)-producing lactic acid bacteria from Thai fermented foods

OBJECTIVES

This study aimed to screen, characterize, and annotate the genome along with the comparison of GABA synthesis genes presented in lactic acid bacteria (LAB).

RESULTS

Thirty-five LAB isolates from fermented foods were screened for GABA production using thin-layer chromatography (TLC). Fifteen isolates produced GABA ranging from 0.07 to 22.94 g/L. Based on their GTG₅ profiles, phenotypic, and genotypic characteristics, isolates LSI1-1, LSI1-5, LSI2-1, LSI2-2, LSI2-3, LSI2-5, and LSM3-1-4 were identified as Lactobacillus plantarum subsp. plantarum; isolate LSM1-4 was Lactobacillus argentoratensis; isolates CAB1-2, CAB1-5, CAB1-7, and LSI1-4 were Lactobacillus pentosus; and CAB1-1, LSM3-1-1 and LSM3-2-3 were Lactobacillus fermentum. Strains LSI2-1 and CAB1-7 from pickled vegetables were selected for genome analysis. The gadA gene (1410 bp, 470aa) was encountered in GABA production of both strains and no other glutamate decarboxylase (GAD) genes were found in the genomes when compared with other LAB strains. The presence of gadA is evidence for GABA production. Strains LSI2-1 and CAB1-7 produced 22.94 g/L and 11.59 g/L of GABA in GYP broth supplemented with 3% (w/v) MSG at 30 °C for 72 h, respectively.

CONCLUSIONS

Our report highlights the characterization of LAB and GABA production of L. plantarum LSI2-1 strain with its GABA synthesis gene. GABA production of strains LSI2-1 and CAB1-7 in GYP broth with 3% (w/v) MSG and comparative GAD genes.

A taxonomic note on the genus Lactobacillus: Description of 23 novel genera, emended description of the genus Lactobacillus Beijerinck 1901, and union of Lactobacillaceae and Leuconostocaceae

The genus Lactobacillus comprises 261 species (at March 2020) that are extremely diverse at phenotypic, ecological and genotypic levels. This study evaluated the taxonomy of Lactobacillaceae and Leuconostocaceae on the basis of whole genome sequences. Parameters that were evaluated included core genome phylogeny, (conserved) pairwise average amino acid identity, clade-specific signature genes, physiological criteria and the ecology of the organisms. Based on this polyphasic approach, we propose reclassification of the genus Lactobacillus into 25 genera including the emended genus Lactobacillus, which includes host-adapted organisms that have been referred to as the Lactobacillus delbrueckii group, Paralactobacillus and 23 novel genera for which the names Holzapfelia, Amylolactobacillus, Bombilactobacillus, Companilactobacillus, Lapidilactobacillus, Agrilactobacillus, Schleiferilactobacillus, Loigolactobacilus, Lacticaseibacillus, Latilactobacillus, Dellaglioa, Liquorilactobacillus, Ligilactobacillus, Lactiplantibacillus, Furfurilactobacillus, Paucilactobacillus, Limosilactobacillus, Fructilactobacillus, Acetilactobacillus, Apilactobacillus, Levilactobacillus, Secundilactobacillus and Lentilactobacillus are proposed. We also propose to emend the description of the family Lactobacillaceae to include all genera that were previously included in families Lactobacillaceae and Leuconostocaceae. The generic term 'lactobacilli' will remain useful to designate all organisms that were classified as Lactobacillaceae until 2020. This reclassification reflects the phylogenetic position of the micro-organisms, and groups lactobacilli into robust clades with shared ecological and metabolic properties, as exemplified for the emended genus Lactobacillus encompassing species adapted to vertebrates (such as Lactobacillus delbrueckii, Lactobacillus iners, Lactobacillus crispatus, Lactobacillus jensensii, Lactobacillus johnsonii and Lactobacillus acidophilus) or invertebrates (such as Lactobacillus apis and Lactobacillus bombicola).

Lactobacillus hegangensis sp. nov., Lactobacillus suibinensis sp. nov., Lactobacillus daqingensis sp. nov., Lactobacillus yichunensis sp. nov., Lactobacillus mulanensis sp. nov., Lactobacillus achengensis sp. nov., Lactobacillus wuchangensis sp. nov., Lactobacillus gannanensis sp. nov., Lactobacillus binensis sp. nov. and Lactobacillus angrenensis sp. nov., isolated from Chinese traditional pickle and yogurt

Fourteen Gram-stain-positive bacterial strains were isolated from Chinese traditional pickle and yogurt. The strains were characterized using a polyphasic taxonomic approach, including 16S rRNA gene sequence analysis, pheS gene sequence analysis, rpoA gene sequence analysis, fatty acid methyl ester analysis, determination of DNA G+C content, determination of average nucleotide identity (ANI), in silico DNA–DNA hybridization (isDDH) and an analysis of phenotypic features. The data demonstrated that the 14 strains represented ten novel species belonging to the genus Lactobacillus , strains 73-4T, 247-3T, 143-4(a)T, 33-1T, 143-6T, 247-4T, 17-4T, 143-1T, 735-2T and M1530-1T were designated as the type strains. Strains 73-4T and 247-3T were phylogenetically related to the type strains of Lactobacillus camelliae and Lactobacillus jixianensis , having 97.0–98.9 % 16S rRNA gene sequence similarities, 83.9–87.2 % pheS gene sequence similarities and 86.8–93.3 % rpoA gene sequence similarities. Strains 143-4(a)T and 33-1T were phylogenetically related to the type strains of Lactobacillus rhamnosus , Lactobacillus paracasei and Lactobacillus casei , having 93.6–96.5 % 16S rRNA gene sequence similarities, 73.9–77.2 % pheS gene sequence similarities and 76.1–77.6 % rpoA gene sequence similarities. Strains 143-6T, 247-4T, 17-4T and 143-1T were phylogenetically related to the type strains of Lactobacillus concavus , Lactobacillus dextrinicus and Lactobacillus bayanensis , exhibiting 95.5–99.9 % 16S rRNA gene sequence similarities, 76.5–83.1 % pheS gene sequence similarities and 83.6–98.3 % rpoA gene sequence similarities. Strain 735-2T was phylogenetically related to the type strains of Lactobacillus zhaoyuanensis , Lactobacillus jiayinensis and Lactobacillus coryniformis , having 98.2–99.1 % 16S rRNA gene sequence similarities, 82.8–84.1 % pheS gene sequence similarities and 93.0–93.9 % rpoA gene sequence similarities. Strain M1530-1T was phylogenetically related to the type strains of Lactobacillus suantsaiihabitans and Lactobacillus brevis , having 99.5 and 99.0 % 16S rRNA gene sequence similarities, 90.3 and 81.7 % pheS gene sequence similarities and 97.7 and 91.1 % rpoA gene sequence similarities. The ANI and isDDH values between strains 73-4T, 247-3T, 143-4(a)T, 33-1T, 143-6T, 247-4T, 17-4T, 143-1T, 735-2T, M1530-1T and type strains of phylogenetically related species were less than 86.8 % and 33.9 % respectively, confirming that they represent ten novel species within the genus Lactobacillus . Based upon the data of polyphasic characterization obtained in the present study, ten novel species, Lactobacillus hegangensis sp. nov., Lactobacillus suibinensis sp. nov., Lactobacillus daqingensis sp. nov., Lactobacillus yichunensis sp. nov., Lactobacillus mulanensis sp. nov., Lactobacillus achengensis sp. nov., Lactobacillus wuchangensis sp. nov., Lactobacillus gannanensis sp. nov., Lactobacillus binensis sp. nov. and Lactobacillus angrenensis sp. nov., are proposed and the type strains are 73-4T (=NCIMB 15177T=CCM 8912T=CCTCC AB 2018407T), 247-3T (=NCIMB 15176T=JCM 33275T), 143-4(a)T (=NCIMB 15173T=CCM 8948T=JCM 33273T=CCTCC AB 2018390T), 33-1T (=NCIMB 15169T=CCM 8947T=JCM 33272T=CCTCC AB 2018405T), 143-6T (=NCIMB 15162T=CCM 8951T=JCM 33274T=CCTCC AB 2018411T), 247-4T (=NCIMB 15155T=CCM 8897T=LMG 31059T=CCTCC AB 2018410T), 17-4T (=NCIMB 15161T=CCM 8946T=JCM 33271T=CCTCC AB 2018406T), 143-1T (=NCIMB 15157T=CCM 8937T=CCTCC AB 2018409T), 735-2T (=NCIMB 15190T=CCM 8925T=LMG 31186T) and M1530-1T (=NCIMB 15150T=CCM 8893T=LMG 31046T=CCTCC AB 2018402T), respectively.

Expression and characterization of glutamate decarboxylase from Lactobacillus brevis HYE1 isolated from kimchi

A putative gene (gadlbhye1) encoding glutamate decarboxylase (GAD) was cloned from Lactobacillus brevis HYE1 isolated from kimchi, a traditional Korean fermented vegetable. The amino acid sequences of GADLbHYE1 showed 48% homology with the GadA family and 99% identity with the GadB family from L. brevis. The cloned GADLbHYE1 was functionally expressed in Escherichia coli using inducible expression vectors. The expressed recombinant GADLbHYE1 was successfully purified by Ni-NTA affinity chromatography, and had a molecular mass of 54 kDa with optimal hydrolysis activity at 55 °C and pH 4.0. Its thermal stability was determined to be higher than that of other GADs from L. brevis, based on its melting temperature (75.18 °C). Kinetic parameters including K_m and V_max values for GADLbHYE1 were 4.99 mmol/L and 0.224 mmol/L/min, respectively. In addition, the production of gamma-aminobutyric acid in E. coli BL21 harboring gadlbhye1/pET28a was increased by adding pyridoxine as a cheaper coenzyme.

Characterization of a Potential Probiotic Lactobacillus brevis RK03 and Efficient Production of γ-Aminobutyric Acid in Batch Fermentation

Lactic acid bacteria were isolated from fish and evaluated for their γ-aminobutyric acid (GABA)-producing abilities. Out of thirty-two isolates, Lactobacillus brevis RK03 showed the highest GABA production ability. The effects of various fermentation parameters including initial glutamic acid level, culture temperature, initial pH, and incubation time on GABA production were investigated via a singleparameter optimization strategy. For industrial large-scale production, a low-cost GABA producing medium (GM) broth was developed for fermentation with L. brevis RK03. We found that an optimized GM broth recipe of 1% glucose; 2.5% yeast extract; 2 ppm each of CaCO₃, MnSO₄, and Tween 80; and 10 μM pyridoxal phosphate (PLP) resulted in a maximum GABA yield of 62,523 mg/L after 88 h following the addition of 650 mM monosodium glutamate (MSG), for a conversion rate of 93.28%. Our data provide a practical approach for the highly efficient and economic production of GABA. In addition, L. brevis RK03 is highly resistant to gastric acid and bovine bile salt. Thus, the discovery of Lactobacillus strains with the ability to synthesize GABA may offer new opportunities in the design of improved health-promoting functional foods.

Hydrogel Film-Immobilized Lactobacillus brevis RK03 for γ-Aminobutyric Acid Production

Hydrogels of 2-hydroxyethyl methacrylate/polyethylene glycol diacrylate (HEMA/PEGDA) have been extensively studied for their use in biomedical and pharmaceutical applications owing to their nontoxic and highly hydrophilic characteristics. Recently, cells immobilized by HEMA/PEGDA hydrogels have also been studied for enhanced production in fermentation. Hydrogel films of HEMA/PEGDA copolymer were generated by Ultraviolet (UV)-initiated photopolymerization. The hydrogel films were used to immobilize viable Lactobacillus brevis RK03 cells for the bioconversion of monosodium glutamate (MSG) to γ-aminobutyric acid (GABA). The mechanical properties and fermentation yields of the L. brevis RK03 cells immobilized on polyacrylate hydrogel films with different monomeric formulations were investigated. Fermentation was carried out in 75 mL de Man, Rogosa and Sharpe (MRS) medium containing various concentrations of MSG. We found that HEMA (93%)/PEGDA (3%) hydrogels (sample H) maximized GABA production. The conversion rate of MSG to GABA reached a maximum value of 98.4% after 240 h. Bioconversion activity gradually declined after 420 h to 83.8% after five cycles of semi-continuous fermentation. Our results suggest that HEMA (93%)/PEGDA (3%) hydrogels have great potential for use in GABA production via semi-continuous fermentation.

Hydrogel Film-Immobilized Lactobacillus brevis RK03 for γ-Aminobutyric Acid Production

Hydrogels of 2-hydroxyethyl methacrylate/polyethylene glycol diacrylate (HEMA/PEGDA) have been extensively studied for their use in biomedical and pharmaceutical applications owing to their nontoxic and highly hydrophilic characteristics. Recently, cells immobilized by HEMA/PEGDA hydrogels have also been studied for enhanced production in fermentation. Hydrogel films of HEMA/PEGDA copolymer were generated by Ultraviolet (UV)-initiated photopolymerization. The hydrogel films were used to immobilize viable Lactobacillus brevis RK03 cells for the bioconversion of monosodium glutamate (MSG) to γ-aminobutyric acid (GABA). The mechanical properties and fermentation yields of the L. brevis RK03 cells immobilized on polyacrylate hydrogel films with different monomeric formulations were investigated. Fermentation was carried out in 75 mL de Man, Rogosa and Sharpe (MRS) medium containing various concentrations of MSG. We found that HEMA (93%)/PEGDA (3%) hydrogels (sample H) maximized GABA production. The conversion rate of MSG to GABA reached a maximum value of 98.4% after 240 h. Bioconversion activity gradually declined after 420 h to 83.8% after five cycles of semi-continuous fermentation. Our results suggest that HEMA (93%)/PEGDA (3%) hydrogels have great potential for use in GABA production via semi-continuous fermentation.

Potential of a lactic acid bacterial starter culture with gamma-aminobutyric acid (GABA) activity for production of fermented sausage

The ability of lactic acid bacterial starter cultures to produce gamma-aminobutyric acid (GABA) during sausage fermentation was studied. Among 305 strains of lactic acid bacteria isolated from kimchi samples, 11 strains were selected as starter candidates based on the following criteria: growth speed, pH lowering ability, and biogenic amine productivity including GABA-producing activity. During in vitro tests, the Y8 (Lactobacillus brevis), O52, and KA20 strains produced 39.00 ± 1.36, 49.73 ± 3.80, and 64.59 ± 0.61 mg/kg of GABA, respectively. Interestingly, although isolate Y8 showed low productivity in vitro, the GABA content it produced during in situ tests (61.30 ± 2.61 mg/kg) was similar to that produced by isolate PM3 (L. brevis) used as positive control (69.64 ± 2.20 mg/kg). Therefore, isolate Y8 was selected as the best functional starter culture for the production of fermented sausage because it exhibited rapid growth, safety, and abundant GABA productivity.

The salted radish takuan-zuke shows antihypertension effects in spontaneously hypertensive rats

Recently, we reported that the antihypertensive compound, γ-aminobutyrate (GABA), increases over time during the dehydration of salted radish, known as takuan-zuke, a popular pickle in Japan.

A Genomic View of Lactobacilli and Pediococci Demonstrates that Phylogeny Matches Ecology and Physiology

Lactobacilli are used widely in food, feed, and health applications. The taxonomy of the genus Lactobacillus, however, is confounded by the apparent lack of physiological markers for phylogenetic groups of lactobacilli and the unclear relationships between the diverse phylogenetic groups. This study used the core and pan-genomes of 174 type strains of Lactobacillus and Pediococcus to establish phylogenetic relationships and to identify metabolic properties differentiating phylogenetic groups. The core genome phylogenetic tree separated homofermentative lactobacilli and pediococci from heterofermentative lactobacilli. Aldolase and phosphofructokinase were generally present in homofermentative but not in heterofermentative lactobacilli; a two-domain alcohol dehydrogenase and mannitol dehydrogenase were present in most heterofermentative lactobacilli but absent in most homofermentative organisms. Other genes were predominantly present in homofermentative lactobacilli (pyruvate formate lyase) or heterofermentative lactobacilli (lactaldehyde dehydrogenase and glycerol dehydratase). Cluster analysis of the phylogenomic tree and the average nucleotide identity grouped the genus Lactobacillus sensu lato into 24 phylogenetic groups, including pediococci, with stable intra- and intergroup relationships. Individual groups may be differentiated by characteristic metabolic properties. The link between phylogeny and physiology that is proposed in this study facilitates future studies on the ecology, physiology, and industrial applications of lactobacilli.

Optimization of γ-aminobutyric acid production by Lactobacillus plantarum Taj-Apis362 from honeybees

Dominant strains of lactic acid bacteria (LAB) isolated from honey bees were evaluated for their γ-aminobutyric acid (GABA)-producing ability. Out of 24 strains, strain Taj-Apis362 showed the highest GABA-producing ability (1.76 mM) in MRS broth containing 50 mM initial glutamic acid cultured for 60 h. Effects of fermentation parameters, including initial glutamic acid level, culture temperature, initial pH and incubation time on GABA production were investigated via a single parameter optimization strategy. The optimal fermentation condition for GABA production was modeled using response surface methodology (RSM). The results showed that the culture temperature was the most significant factor for GABA production. The optimum conditions for maximum GABA production by Lactobacillus plantarum Taj-Apis362 were an initial glutamic acid concentration of 497.97 mM, culture temperature of 36 °C, initial pH of 5.31 and incubation time of 60 h, which produced 7.15 mM of GABA. The value is comparable with the predicted value of 7.21 mM.

Lactobacillus heilongjiangensis sp. nov., isolated from Chinese pickle

A Gram-stain-positive bacterial strain, S4-3T, was isolated from traditional pickle in Heilongjiang Province, China. The bacterium was characterized by a polyphasic approach, including 16S rRNA gene sequence analysis, pheS gene sequence analysis, rpoA gene sequence analysis, dnaK gene sequence analysis, fatty acid methyl ester (FAME) analysis, determination of DNA G+C content, DNA–DNA hybridization and an analysis of phenotypic features. Strain S4-3T showed 97.9–98.7 % 16S rRNA gene sequence similarities, 84.4–94.1 % pheS gene sequence similarities and 94.4–96.9 % rpoA gene sequence similarities to the type strains of Lactobacillus nantensis , Lactobacillus mindensis , Lactobacillus crustorum , Lactobacillus futsaii , Lactobacillus farciminis and Lactobacillus kimchiensis . dnaK gene sequence similarities between S4-3T and Lactobacillus nantensis LMG 23510T, Lactobacillus mindensis LMG 21932T, Lactobacillus crustorum LMG 23699T, Lactobacillus futsaii JCM 17355T and Lactobacillus farciminis LMG 9200T were 95.4, 91.5, 90.4, 91.7 and 93.1 %, respectively. Based upon the data obtained in the present study, a novel species, Lactobacillus heilongjiangensis sp. nov., is proposed and the type strain is S4-3T ( = LMG 26166T = NCIMB 14701T).

Lactobacillus yonginensis sp. nov., a lactic acid bacterium with ginsenoside converting activity isolated from Kimchi

A Gram-reaction-positive, non-motile, non-spore-forming, catalase-negative, facultatively anaerobic, rod-shaped, β-glucosidase-producing lactic acid bacterium, designated strain THK-V8T, was isolated from the Korean fermented food, Kimchi, and its taxonomic position was investigated by using a polyphasic approach. Strain THK-V8T was able to grow at 4–40 °C (optimum, 30 °C) and pH 4.0–7.0 (optimum, pH 6.0). Strain THK-V8T had the ability to transform ginsenoside Rb1 to Rd. On the basis of 16S rRNA gene sequence similarity data, strain THK-V8T was shown to belong to the genus Lactobacillus . Strain THK-V8T was related to Lactobacillus koreensis DCY50T (98.8 % sequence similarity), Lactobacillus parabrevis LMG 11984T (97.7 %), Lactobacillus senmaizukei L13T (97.5 %), Lactobacillus hammesii TMW1.1236T (97.3 %) and Lactobacillus brevis ATCC 14687T (97.2 %). Subsequently, sequence analysis of the RNA polymerase alpha subunit gene (rpoA) confirmed that strain THK-V8T showed a maximum rpoA gene sequence similarity value of 93 % with Lactobacillus brevis LMG 6906T. The G+C content of the genomic DNA was 47.8 mol%. The DNA–DNA hybridization values between strain THK-V8T and Lactobacillus parabrevis DCY50T and Lactobacillus parabrevis LMG 11984T were 46.1±4.9 % and 10.6±2.9 %, respectively. The major fatty acids were summed feature 7 (comprised of C19 : 0 cyclo ω10c/19ω6), C14 : 0, C16 : 0 and C18 : 1ω9c. The cell wall peptidoglycan was of the A4α l-Lys–d-Asp type. The phenotypic and molecular properties indicated that strain THK-V8T represents a novel species within the genus Lactobacillus , for which the name Lactobacillus yonginensis sp. nov. is proposed. The type strain is THK-V8T ( = KACC 16236T = JCM 18023T).

Lactobacillus koreensis sp. nov., isolated from the traditional Korean food kimchi

A lactic acid bacterium, strain DCY50T, isolated from the traditional Korean food kimchi, was studied to determine its taxonomic position. The strain was Gram-stain-positive, catalase-negative, facultatively anaerobic, rod-shaped and motile. The genomic DNA G+C content was 49 mol% and the peptidoglycan structure was of the A4α (l–Lys–d-Asp) type. Chemotaxonomic markers of the strain were consistent with its classification in the genus Lactobacillus. Comparisons of 16S rRNA and rpoA gene sequences showed that strain DCY50T was most closely related to the type strains of Lactobacillus parabrevis (98.4 and 91.6 % similarity, respectively, for the 16S rRNA and rpoA genes), L. hammesii (98.0 and 91.2 %), L. brevis (97.6 and 93.3 %) and L. senmaizukei (97.4 and 90.5 %). DNA–DNA relatedness of strain DCY50T to these type strains was below 36 %. According to the genotypic and phenotypic data, strain DCY50T could be differentiated from all known Lactobacillus species and should be classified in a novel species, for which the name Lactobacillus koreensis sp. nov. is proposed; the type strain is DCY50T ( = KCTC 13530T  = JCM 16448T).