Comparative acid tolerances and inhibitor sensitivities of isolated F-ATPases of oral lactic acid bacteria.

pH activity profiles and inhibitor sensitivities were compared for membrane ATPases isolated from three oral lactic acid bacteria, Lactobacillus casei ATCC 4646, Streptococcus mutans GS-5, and Streptococcus sanguis NCTC 10904, with, respectively, high, moderate, and low levels of acid tolerance. Membranes containing F1F0 ATPases were isolated by means of salt lysis of cells treated with muralytic enzymes. Membrane-free F1F0 complexes were then isolated from membranes by detergent extraction with Triton X-100 or octylglucoside. Finally, F1 complexes free of the proton-conducting F0 sector were obtained by washing membranes with buffers of low ionic strength. The pH activity profiles of the membrane-associated enzymes reflected the general acid tolerances of the organisms from which they were isolated; for example, pH optima were approximately 5.5, 6.0, and 7.0, respectively, for enzymes from L. casei, S. mutans, and S. sanguis. Roughly similar profiles were found for membrane-free F1F0 complexes, which were stabilized by phospholipids against loss of activity during storage. However, profiles for F1 enzymes were distinctly narrower, indicating that association with F0 and possibly other membrane components enhanced tolerance to both acid and alkaline media. All of the enzymes were found to have similar sensitivities to Al-F complexes, but only F1F0 enzymes were highly sensitive to dicyclohexylcarbodiimide. The procedures described for isolation of membrane-free F1F0 forms of the enzymes from oral lactic acid bacteria will be of use in future studies of the characteristics of the enzymes, especially in studies with liposomes.     

Comparative studies of lactic acid dehydrogenases in lactic acid bacteria

The stability, pH-dependence and kinetic properties of the Mn²⁺ and FDP-activated NAD-dependent lactic acid dehydrogenases from Lactobacillus casei ssp. casei (ATCC 393) and L. curvatus (DSM) 20010) were studied after the enzymes were purified to homogeneity by affinity chromatography. Both enzymes are virtually unidirectional, catalysing efficiently only the reduction of pyruvate. They are similar with respect to the effector requirement and pH-optimum. They differ, however, in their electrophoretic mobility, heat stability, pH-dependence of the Mn²⁺ requirement and several kinetic properties. It is suggested that most of these differences are caused by differences of the negative charges in the vicinity of the FDP-binding site or the site responsible for the interaction of the subunits of the enzymatically active oligomeres.Abbreviations l-LDH l-Lactic acid dehydrogenase - FDP Fructose-1,6-bisphosphate - DTE Dithioerythrol AddendumIn the case of the L. casei-LDH the shape of the NADH saturation curve is not changed by omitting the effectors FDP and Mn 2⁺. The K _M under these conditions is 3 fold higher (10.10 ^–5 M).     

Characterization of lactic acid bacteria isolated from seafood

Lactic acid bacteria were isolated from various samples of seafood: fresh pollock, brine shrimp, gravad fish, vacuum-packed seafood (surimi, smoked tuna, salted cod), and fish stored under 100% CO₂ at 5°C (smoked tuna, fresh and salted cod, salmon). Eighty-six independent isolates were obtained and were grouped according to cell morphology, presence or absence of diaminopimelic acid in the cell wall, and lactate configuration. Fifty-four isolates were identified as belonging to the genus Lactococcus and most of them exhibited DNA homologies with L. lactis subsp. lactis. Four strains were identified as Lactobacillus plantarum , eight strains as genus Leuconostoc and 16 belonged to the genus Carnobacterium. One facultative heterofermentative Lactobacillus and three other isolates were not identified. Of the strains 47% showed similar patterns of carbohydrate fermentations especially among strains belonging to the genera Lactococcus and Carnobacterium. Most of the strains (64%) grew at 5°C, in salted media and in fish extract medium without added sugar. Carnobacterium piscicola and Carn. divergens were the only reference strains able to grow in the same conditions as well as psychrotroph strains isolated from seafood. A numerical analysis could not be used because of the divergent properties of isolates of the same genus and strong similarities between different genera.     

Probiotic characteristics of lactic acid bacteria isolated from kimchi

Aims: The present work was aimed at identifying strains of lactic acid bacteria (LAB) from kimchi, with properties suitable for use as starter cultures in yogurt fermentation. Methods and Results: A total of 2344 LAB strains were obtained from two different sources, one group consisted of commercial LAB strains from kimchi, and the second group consisted of those strains isolated from various types of kimchi. The LAB strains from both groups were screened for resistance to biological barriers (acid and bile salts), and the four most promising strains were selected. Further analysis revealed that KFRI342 of the four selected strains displayed the greatest ability to reduce the growth of the cancer cells, SNU‐C4. The in vivo efficacy of strains in quinone reductase induction assay was evaluated, and the extent of DNA strand breakage in individual cells was investigated using the comet assay. Strain KFRI342 was identified as Lactobacillus acidophilus by 16S rRNA sequence analysis, showed protection against tumour initiation and imparted immunostimulation as well as protection against DNA damage. Conclusions: Strain KFRI342, which showed probiotic characteristics reducing cancer cell growth, could be a suitable starter culture for yogurt fermentation because of its strong acid production and high acid tolerance. Significance and Impact of the Study: This is the first report to describe a bacterium, isolated from kimchi, Lact. acidophilus KFRI342 which has the probiotic characteristics and the acid tolerance needed for its use as a starter culture in yogurt fermentation.     

Characteristics of lactic acid bacteria isolated from vacuum-packaged beef

The characteristics of 177 psychrotrophic lactic acid bacteria isolated from vacuum-packaged fresh beef have been studied. Eighteen isolates were identified as Leuconostoc mesenteroides and the remainder were lactobacilli. None of these could be identified down to a species level and they were considered to be atypical streptobacteria or atypical betabacteria. Atypical streptobacteria produced both isomers of lactic acid and did not ferment lactose and maltose. Atypical beta-bacteria produced only L(+) lactic acid. The nature of the isolates varied considerably from pack to pack. The API 50 lactobacillus identification system proved useful in studying these organisms.     

Safety and probiotic functionality of isolated goat milk lactic acid bacteria

Purpose

Lactic acid bacteria (LAB) are traditionally employed in the food industry. LAB strains from goat milk may also present probiotic potential, and it is fundamental to study the safety and functionality aspects which are desirable for their use in food. The objective of this study was to verify the probiotic potential of lactic bacteria isolated from goat milk.

Methods

The presence of safety-related virulence factors (hemolytic activity, gelatinase production, coagulase, and sensitivity to antibiotics) as well as functionality (exopolysaccharide (EPS) production, proteolytic activity, autoaggregation, gas production, survival in the gastrointestinal tract, and antimicrobial activity against bacteria that impair oral health) were determined.

Result

The selected LAB strains are safe against the evaluated parameters and have characteristics of possible probiotic candidates. Especially L. plantarum (DF60Mi) and Lactococcus lactis (DF04Mi) have potential to be added to foods because they have better resistance to simulated gastrointestinal conditions. In addition, they are isolated with already proven antimicrobial activity against Listeria monocytogenes, an important food-borne pathogen. DF60Mi was able to produce EPS (exopolysaccharides). LS2 and DF4Mi strains, both Lactococcus lactis subsp. lactis, demonstrated antimicrobial activity against S. mutans ATCC 25175, a recurrent microorganism in oral pathologies, mainly caries.

Conclusion

This study provides subsidies for future exploration of the potentialities of these LAB strains for both the development of new functional foods and for application in oral health.

     

Antibacterial activity of lactic acid bacteria isolated from vacuum-packaged meats

Lactic acid bacteria isolated from vacuum-packaged fresh meat stored at 4°C were shown to produce antagonistic substances active against closely related bacteria. Growth medium, pH and growth temperature all affected the production of the inhibitory substances. Ten strains including aciduric Lactobacillus -type organisms, Carnobacterium spp. and Leuconostoc spp. were selected that produced protein-aceous substances that caused inhibition of indicator strains. These were considered to be bacteriocins or bacteriocin-like compounds based on their inactivation with protease, generally narrow spectra of antibacterial activity and bactericidal or bacte-riostatic modes of action. Activity was not lost from supernatant fluids as a result of heat treatment at 62°C for 30 min, except for the Leuconostoc strains. Inhibitory spectra of some strains included Enterococcus spp. and Listeria monocytogenes . Some strains were of interest because their inhibitory substances were detected in the supernatant fluid early in the growth cycle. The inhibitory substances differed in characteristics between strains and there is evidence that more than one bacteriocin-like substance may be produced by some strains.     

Identification of lactic acid bacteria isolated from human blood cultures

Fifteen lactic acid bacterial strains were isolated from blood cultures from 15 different patients in the Faculty Hospital in Brno, Czech Republic. All strains were identified using biochemical tests and repetitive PCR using the (GTG)5 primer. Doubtful identification results were confirmed by whole-cell protein analysis. The strains were assigned to the genera Lactobacillus (eight strains representing seven species), Leuconostoc (six strains representing four species) and Weissella (one strain). Antibiotic susceptibility testing was performed using the E-test and revealed high-level resistance to cotrimoxazol, metronidazole, vancomycin and teicoplanin, but nearly all strains were susceptible to erythromycin, clindamycin, ampicillin and penicillin.     

酸马奶中乳酸菌的鉴定及生物学特性的研究

[目的]对从酸马奶中分离出来的10株乳酸菌进行鉴定和生理生化特性研究,为工业生产筛选特性优良的菌种.[方法]通过形态学观察、生理生化特性、分子生物学特性及其对致病菌抑制作用的研究对其进行鉴定,并筛选特性优良菌株.[结果]10株乳酸菌分别为2株Lactobacillus plantarum、2株Enterococcus villorum、2株Enterococcus dispar、3株Enterococcus durans和1株Enterococcus raffinosus;其对Staphylococcus aureus、Escherichia coli和Enteritidis bacillus有不同程度的抑制作用.[结论]菌株HZ24、HZ25具有良好的生物学特性和益生功能,可以应用到食品发酵工业生产中.     

Antibacterial activity of lactic acid bacteria isolated from vacuum-packaged meats

Lactic acid bacteria isolated from vacuum-packaged fresh meat stored at 4 degrees C were shown to produce antagonistic substances active against closely related bacteria. Growth medium, pH and growth temperature all affected the production of the inhibitory substances. Ten strains including aciduric Lactobacillus-type organisms, Carnobacterium spp. and Leuconostoc spp. were selected that produced protein-aceous substances that caused inhibition of indicator strains. These were considered to be bacteriocins or bacteriocin-like compounds based on their inactivation with protease, generally narrow spectra of antibacterial activity and bactericidal or bacteriostatic modes of action. Activity was not lost from supernatant fluids as a result of heat treatment at 62 degrees C for 30 min, except for the Leuconostoc strains. Inhibitory spectra of some strains included Enterococcus spp. and Listeria monocytogenes. Some strains were of interest because their inhibitory substances were detected in the supernatant fluid early in the growth cycle. The inhibitory substances differed in characteristics between strains and there is evidence that more than one bacteriocin-like substance may be produced by some strains.     

Preliminary characterization of lactic acid bacteria isolated from Zlatar cheese

AIMS: Isolation, characterization and identification of lactic acid bacteria (LAB) from artisanal Zlatar cheese during the ripening process and selection of strains with good technological characteristics. METHODS AND RESULTS: Characterization of LAB was performed based on morphological, physiological and biochemical assays, as well as, by determining proteolytic activity and plasmid profile. rep-polymerase chain reaction (PCR) analysis and 16S rDNA sequencing were used for the identification of LAB. PCR analysis was performed with specific primers for detection of the gene encoding nisin production. Strains Lactobacillus paracasei subsp. paracasei, Lactobacillus plantarum, Lactobacillus brevis, Lactococcus lactis subsp. lactis, Enterococcus faecium and Enterococcus faecalis were the main groups present in the Zlatar cheese during ripening. CONCLUSIONS: Temporal changes in the species were observed during the Zlatar cheese ripening. Mesophilic lactobacilli are predominant microflora in Zlatar cheese. SIGNIFICANCE AND IMPACT OF THE STUDY: In this study we determined that Zlatar cheese up to 30 days old could be used as a source of strains for the preparation of potential starter cultures in the process of industrial cheese production. As the Serbian food market is adjusting to European Union regulations, the standardization of Zlatar cheese production by using starter culture(s) based on autochtonous well-characterized LAB will enable the industrial production of this popular cheese in the future.     

Identification of lactic acid bacteria isolated from human vaginal secretions

A total of 57 lactic acid bacteria were isolated from the vaginal secretions of 259 patients. Of these strains, 37 were isolated from patients attending pre-natal clinics and the remaining strains from patients attending post-natal clinics. The strains were identified by using simple physiological and biochemical tests and their phenotypic relatedness determined by numerical analysis of total soluble cell protein patterns. The genotypic relatedness of representative strains selected from each of the protein profile clusters was determined by numerical analysis of the DNA banding patterns obtained from RAPD-PCR. The majority of lactobacilli isolated belonged to the species Lactobacillus pentosus, Lactobacillus fermentum and Enterococcus faecium. A few strains of Lactobacillus plantarum and Weissella viridescens were also isolated. One strain, TV 1029, grouped into the same protein profile cluster as E. faecium, but revealed a DNA banding pattern closer related to Enterococcus faecalis. This is the first report of W. viridescens associated with the human vagina. This revised version was published online in June 2006 with corrections to the Cover Date.     

Biogenic amine production by lactic acid bacteria isolated from cider

AIMS: To study the occurrence of histidine, tyrosine and ornithine decarboxylase activity in lactic acid bacteria (LAB) isolated from natural ciders and to examine their potential to produce detrimental levels of biogenic amines. METHODS AND RESULTS: The presence of biogenic amines in a decarboxylase synthetic broth and in cider was determined by reversed-phase high-performance liquid chromatography (RP-HPLC). Among the 54 LAB strains tested, six (five lactobacilli and one oenococci) were biogenic amine producers in both media. Histamine and tyramine were the amines formed by the LAB strains investigated. Lactobacillus diolivorans were the most intensive histamine producers. This species together with Lactobacillus collinoides and Oenococcus oeni also seemed to produce tyramine. No ability to form histamine, tyramine or putrescine by Pediococus parvulus was observed, although it is a known biogenic amine producer in wines and beers. CONCLUSIONS: This study demonstrated that LAB microbiota growing in ciders had the ability to produce biogenic amines, particularly histamine and tyramine, and suggests that this capability might be strain-dependent rather than being related to a particular bacterial species. SIGNIFICANCE AND IMPACT OF THE STUDY: Production of biogenic amines by food micro-organisms has continued to be the focus of intensive study because of their potential toxicity. The main goal was to identify the microbial species capable of producing these compounds in order to control their presence and metabolic activity in foods.     

Safety of industrial lactic acid bacteria.

Lactic acid bacteria (LAB) are ubiquitous in fermented and non-fermented foods and are common components of the human commensal microflora. This long history of human exposure and consumption has led to the reasonable conclusion that they are generally safe. Recent attention has also focused on their possible role as probiotic bacteria, promoting beneficial health effects. There have, however, been a number of reports of human infections caused by LAB and these are reviewed. In most cases, the source of the infection was the commensal LAB flora rather than ingested bacteria and the patient had some underlying disease or predisposing condition. Even as opportunistic pathogens, the LAB, with the notable exception of the enterococci, are much less successful than a number of other members of the commensal microflora. The use of new strains for probiotic use is likely to require more detailed evidence for their safety, particularly if the strains have been genetically modified or have been derived from animals. Procedures that have been proposed for assessing the safety of new strains are described.     

Antimicrobial susceptibility of lactic acid bacteria isolated from a cheese environment

In the production of the Spanish traditional blue-veined Cabrales cheese, lactic acid bacteria strains free of antibiotic resistance that have a transferrable capacity are necessary as components of a specific starter. To select for these bacteria, the minimum inhibitory concentration (MIC) of 12 antibiotics and 2 mixtures (containing beta-lactamase inhibitor and penicillin) were determined by microbroth and agar dilution techniques in 146 strains belonging to the genera Lactococcus, Enterococcus, Lactobacillus, and Leuconostoc. The antibiotic-resistance profiles of Lactococcus and Enterococcus species were different from those of Lactobacillus and Leuconostoc, but clear genus- or species-associated patterns were not observed. Cefoxitin and metronidazole were not effective against bacteria of these genera. The MICs of beta-lactam antibiotics for lactobacilli and leuconostoc isolates were higher than those for lactococci and enterococci, but no strain was clinically resistant. All lactobacilli and leuconostoc isolates were resistant to high levels of vancomycin, a type of resistance not seen among the tested members of the genera Lactococcus and Enterococcus. The majority of the observed resistance appeared to be either intrinsic or nonspecific, although some strains of Lactococcus lactis, Enterococcus spp., and Lactobacillus spp. were resistant to antibiotics, such as chloramphenicol, erythromycin, clindamycin, or tetracycline.     

Bio-protective potential of lactic acid bacteria isolated from fermented wax gourd

The antifungal activities of 85 lactic acid bacteria strains isolated from fermented wax gourd against the four fungal species, Penicillium oxalicum, Aspergillus flavus, Aspergillus sydowii, and Mucor racemosus, were determined. Inhibitory activity against at least one or more fungal species was observed with 27 Weissella cibaria and 11 Weissella paramesenteroides strains. Among these strains, W. cibaria 861006 and W. paramesenteroides 860509 showed greater inhibitory activities and were therefore selected for further analysis. The results suggested that the antifungal activities were originated from the organic acids produced by W. cibaria 861006 and W. paramesenteroides 860509. The application tests indicated that the growth of P. oxalicum could be effectively inhibited by W. cibaria 861006 for 6 days on grape surfaces. However, W. paramesenteroides 860509 could only remain its inhibition effect for 48 h. The findings obtained in this study suggest the potential use of W. cibaria 861006 as a bio-protective agent against fungi for agricultural purposes or ready-to-eat fresh fruit and vegetable products.