Lactic Acid Bacterial Strains Research Articles

Modeling of lactic acid fermentation of leguminous plant juices

Lactic acid fermentation of leguminous plant juices was modeled to provide a comparative efficiency assessment of the previously selected strains of lactic acid bacteria as potential components of starter cultures. Juices of the legumes fodder galega, red clover, and alfalfa were subjected to lactic acid fermentation in 27 variants of experiment. Local strains (Lactobacillus sp. RS 2, Lactobacillus sp. RS 3, and Lactobacillus sp. RS 4) and the collection strain Lactobacillus plantarum BS 933 appeared the most efficient (with reference to the rate and degree of acidogenesis, ratio of lactic and acetic acids, and dynamics of microflora) in fermenting fodder galega juice; Lactobacillus sp. RS 1, Lactobacillus sp. RS 2, Lactobacillus sp. RS 3, Lactobacillus sp. RS 4, and L. plantarum BS 933 were the most efficient for red clover juice. Correction of alfalfa juice fermentation using the tested lactic acid bacterial strains appeared inefficient, which is explainable by its increased protein content and a low level of the acids produced during fermentation.

The effect of prebiotics on production of antimicrobial compounds, resistance to growth at low pH and in the presence of bile, and adhesion of probiotic cells to intestinal mucus

Screening of five bile salt-resistant and low pH-tolerant lactic acid bacteria for inhibitory activity against lactic acid bacteria and bacterial strains isolated from the faeces of children with HIV/AIDS. Determining the effect of prebiotics and soy milk-base on cell viability and adhesion of cells to intestinal mucus. Lactobacillus plantarum 423, Lactobacillus casei LHS, Lactobacillus salivarius 241, Lactobacillus curvatus DF 38 and Pediococcus pentosaceus 34 produced the highest level of antimicrobial activity (12,800 AU ml(-1)) when grown in MRS broth supplemented with 2% (m/v) dextrose. Growth in the presence of Raftilose Synergy1, Raftilose L95 and Raftiline GR did not lead to increased levels of antimicrobial activity. Cells grown in the presence of Raftilose Synergy1 took longer to adhere to intestinal mucus, whilst cells grown in the absence of prebiotics showed a linear rate of binding. A broad range of gram-positive and gram-negative bacteria were inhibited. Dextrose stimulated the production of antimicrobial compounds. Adhesion to intestinal mucus did not increase with the addition of prebiotics. The strains may be incorporated in food supplements for HIV/AIDS patients suffering from gastro-intestinal disorders.

Probiotics Down-Regulate flaA σ28 Promoter in Campylobacter jejuni

Lactobacilli and bifidobacteria are important members of the gastrointestinal microflora of humans and animals and are thought to have positive effects on human health. Therefore, there is an increasing interest in using these microorganisms as probiotics to be incorporated into either fermented dairy products or tablets. However, convincing scientific data that support claims of their health benefits are scarce. The effect of cell-free extracts of milk fermented by 10 probiotic bacteria (five Bifidobacterium strains and five Lactobacillus strains) on the expression of the flaA gene of Campylobacter jejuni was assessed using a fusion between the flaA σ28 promoter and a promoterless luxCDABE cassette carried on the plasmid pRYluxCDABE, which resulted in strains with quantifiable luminescence linked to flaA σ28 promoter activity. Cell-free extracts of milk fermented by all of the tested probiotic strains inhibited the growth of the C. jejuni and down-regulated flaA σ28 promoter activity. Two nonprobiotic lactic acid bacterial strains, Lactococcus lactis and Streptococcus thermophilus, were less inhibitory.

Leuconostoc durionis sp. nov., a heterofermenter with no detectable gas production from glucose

Three lactic acid bacterial (LAB) strains obtained from a Malaysian acid-fermented condiment, tempoyak (made from pulp of the durian fruit), showed analogous but distinct patterns after screening by SDS-PAGE of whole-cell proteins and comparison with profiles of all recognized LAB species. 16S rRNA gene sequencing of one representative strain showed that the taxon belongs phylogenetically to the genus Leuconostoc, with its nearest neighbour being Leuconostoc fructosum (98 % sequence similarity). Biochemical characteristics and DNA-DNA hybridization experiments demonstrated that the strains differ from Leuconostoc fructosum and represent a single, novel Leuconostoc species for which the name Leuconostoc durionis sp. nov. is proposed. The type strain is LMG 22556(T) (= LAB 1679(T) = D-24(T) = CCUG 49949(T)).

Potential of selected lactic acid bacteria to produce food compatible antifungal metabolites

The aim of this study was to assess the potential of lactic acid bacteria to inhibit the outgrowth of some common food-spoiling fungi. Culture supernatants of 17 Lactic acid bacterial strains as well as of three commercial probiotic cultures were evaluated for antifungal activity using an agar-diffusion method. The method parameters were chosen in order to reveal compounds for potential use in food (bio)preservation. Thirteen strains showed antifungal activity of which five strains were very promising: Lactobacillus acidophilus LMG 9433, L. amylovorus DSM 20532, L. brevis LMG 6906, L. coryniformis subsp. coryniformis LMG 9196 and L. plantarum LMG 6907. Four of these five strains were further examined; it was found that the produced antifungal metabolites were pH-dependent. The exact chemical nature of these substances has not been revealed yet.

Gene organization and sequences of pediocin AcH/PA-1 production operons in Pediococcus and Lactobacillus plasmids

To determine the locations and sequences of pediocin AcH production genes in Pediococcus parvulus ATO77 from vegetables, Lactobacillus plantarum WHE92 from Muenster cheese, and a lactose-fermenting isolate Pediococcus pentosaceus S34 from buffalo milk. Plasmid curing, Southern blot hybridization, and DNA sequence analysis indicate that pediocin AcH production genes are encoded by highly similar operons in unique plasmids designated pATO77 from P. parvulus ATO77, pS34 from P. pentosaceus S34, and pWHE92 from Lact. plantarum WHE92. Structure, immunity and secretion system genes are linked together in the operons, and the promoter sequences are the same. The amino acid sequences of the encoded proteins are highly conserved between plasmids. Pediocin AcH production genes are located within a plasmid-borne operon cassette in all lactic acid bacterial strains examined to date. All four genes needed for production are present within a single plasmid in each strain. This is the first demonstration that the expression of a class IIa bacteriocin is directed by a common gene cassette that has been disseminated to unique plasmids in different genera of lactic acid bacteria. These plasmids should be useful for expressing pediocin AcH in Pediococcus and Lactobacillus strains used in food production.

Molecular identification and anti-pathogenic activities of putative probiotic bacteria isolated from faeces of healthy elderly individuals

One hundred and nine lactic acid bacterial strains (56 bifidobacteria-like and 53 lactobacilli-like) were isolated from faecal samples donated by healthy elderly individuals (>65 years old). Isolates were identified to species level by phenotypic analysis (by API) and by 16S rDNA sequencing. Eleven species of Lactobacillus and six species of Bifidobacterium were identified. The most frequently isolated lactobacillus was L. fermentum and the most frequently isolated bifidobacterium was closely related to B. infantis by 16S rDNA sequence alignment. The isolates were characterized for their antimicrobial activity against Clostridium difficile , enteropathogenic Escherichia col i (EPEC), verocytotoxigenic E. coli (VTEC) and Campylobacter jejuni . The lactobacilli displayed variations in their antimicrobial activity with few strains showing inhibitory activity against all pathogens. The bifidobacteria displayed higher levels of inhibitory activity against C. jejuni and Cl. difficile than against the E. coli strains. Keywords : Lactobacillus, Bifidobacterium, elderly, gastrointestinal microbiota, inhibition, Clostridium difficile, enteropathogenic Escherichia coli (EPEC), verocytotoxigenic E. coli (VTEC), Campylobacter jejuni .

Molecular quantification of lactic acid bacteria in fermented milk products using real-time quantitative PCR

Real-time quantitative PCR assays were developed for the absolute quantification of lactic acid bacteria (LAB) ( Streptococcus thermophilus, Lactobacillus delbrueckii, L. casei, L. paracasei, L. rhamnosus, L. acidophilus and L. johnsonii) in fermented milk products. The results of molecular quantification and classic bacterial enumeration did not differ significantly with respect to S. thermophilus and the species of the L. casei group which were detected in the six commercial fermented products tested, thus showing that DNA extraction was efficient and that genomic DNA solutions were free of PCR inhibitors. For L. delbrueckii, the results of bacterial enumeration were generally lower by a factor 10 to 100 than those of PCR quantification, suggesting a loss of viability during storage of the dairy products at 1–8 °C for most of the strains in this species. Real-time quantitative assays enabled identification of the species of lactic acid bacterial strains initially present in commercial fermented milk products and their accurate quantification with a detection threshold of 10 3 cells per ml of product.

English

Diversity and density of lactic acid bacteria isolated from Algerian raw goats' milk in arid zones were studied by determination of morphological, cultural, physiological and biochemical characteristics. 206 lactic acid bacterial strains were isolated, with 115 of them belonging to lactic acid cocci and others to the genus, Lactobacillus. The representative species of the total cocci were Lactococcus sp. (76.16%), Streptococcus thermophilus (14.78%) and Leuconostoc sp. (8.6%). The dominating species is Lactococcus lactis subsp. Lactis. Lactobacilli species found in local raw goats' milk and their proportion were: Lb. curvatus (25.25%), Lb. helviticus (10.98%), Lb. plantarum (9.89%), Lb. reuteri (9.89%), Lb. casei (7.69%), Lb. brevis (5.49%), Lb. bulgaricus (5.49%) Lb. paracasei (4.39%) and Lb. acidophilus (2.19%).

Isolation, identification and characterisation of the dominant microorganisms of kule naoto: the Maasai traditional fermented milk in Kenya

From 22 samples of kule naoto, the traditional fermented milk products of the Maasai in Kenya, 300 lactic acid bacterial strains were isolated and phenotypically characterised by their ability to ferment different carbohydrates and by additional biochemical tests. Lactic acid bacteria (LAB), especially the genus Lactobacillus, followed by Enterococcus, Lactococcus and Leuconostoc, dominated the microflora of these samples. The major Lactobacillus species was Lactobacillus plantarum (60%), with a lower frequency of isolation for Lactobacillus fermentum, Lactobacillus paracasei and Lactobacillus acidophilus. Most strains produced enzymes such as β-galactosidase and peptidases, which are of relevance to cultured dairy product processing, and exhibited similar patterns of enzymatic activity between species. Enterobacteriaceae could not be detected in 15 out of 22 samples (detection level 10 2/ml). Conversely, yeasts (detection level 10 1/ml) were detected in those samples in which Enterobacteriaceae were not found. The pH values of all these samples were <4.5.

Influence of nutrients on growth and bacteriocin production by Leuconostoc mesenteroides L124 and Lactobacillus curvatus L442.

The aim of this study was to investigate the effect of complex nutrients on microbial growth and bacteriocin production, in order to improve bacteriocin synthesis during the growth cycle of Leuconostoc mesenteroides L124 and Lactobacillus curvatus L442. The fermentations were conducted at the optimum pH and temperature for bacteriocin production (pH 5.5+/-0.1 and temperature 25+/-0.1 degrees C). Because of their association with the final biomass, conditions favouring the increase of the produced biomass resulted in the increase of bacteriocin activity in the growth medium. Since the produced final biomass and the final concentration of the bacteriocins were associated with the amount of the carbon (glucose) and nitrogen source, better growth of the lactic acid bacterial strains favoured the increase of the specific bacteriocin production. Additionally, the bacteriocin production was influenced by carbon/nitrogen ratio.

Identification of 3-Phenyllactic Acid As a Possible Antibacterial Substance Produced by Enterococcus faecalis TH10

Enterococcus faecalis TH10 is a lactic acid bacterial strain isolated from the Malaysian traditional fermented food, “tempeh”, and has antibacterial activity against various pathogens. To identify the antibacterial substance, the butanol extract of the culture supernatant of E. faecalis TH10 was fractionated by HPLC equipped with a reversed-phase partition column, and the elutes were subjected to antibacterial assay. As the activity was observed in a fraction eluted by ca 80% methanol, the fraction was analyzed by gas chromatography/mass spectrometry and 3-phenyllactic acid was identified as the major compound. Fractionation with an optical isomer separation column showed that the preparation contained D-and L-forms of 3-phenyllactic acid at a ratio of 2: 1. Authentic 3-phenyllactic acid showed antibacterial activity against various bacteria such as Staphylococcus aureus and Escherichia coil. These results suggest the possibility that 3-phenyllactic acid is a biopreservative.

Hydrolysis of Isoflavones and Consumption of Oligosaccharides during Lactic Acid Fermentation of Soybean Milk

Aiming to select suitable strains of lactic acid bacteria for producing yogurt-like functional food from soybean milk, the fermentation properties of 14 lactic acid bacterial strains belonging to genera Bifidobacterium, Lactobacillus, Lactococcus and Streptococcus were evaluated using soybean milk as the culture medium. All 14 strains examined were able to grow in soybean milk. Twelve out of the 14 strains lowered the pH of the medium and produced lactic acid. Tested strains showed a variety of consumption patterns of oligosaccharides and hydrolyzing capacity of isoflavone glucosides. Three strains, Bifidobacterium breve JCM 1192, B. bifidum JCM 1255 and Lb. casei subsp. rhamnosus IFO 3425 exhibited the most promising results. These strains could hydrolyze both daidzin and genistin to corresponding aglycones, and consume raffinose and stachyose in addition to lowering the pH and producing lactic acid.

Antioxidant Activity and Optimal Manufacturing Conditions of Purple Sweet Potato Lactic Acid Bacteria Drink

In the current studies, we produced a purple sweet potato lactic acid bacteria drink (PSPLABD) using a variety of lactic acid bacterial strains. The various PSPLABD were analyzed for color, pH, and flavor. We found that Lactobacillus helveticus B-1 was the most efficient strain for fermentation. In addition, optimal conditions included a purple sweet potato content of 10%, a skim milk content of 7%, a white sugar content of 7.5%, fermentation at 35°C, and a pH adjusted to 3.5 (fermentation time ∼24 h). PSPLABD had 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activity (IC50 = 130 μl) and inhibited lipid peroxidation (equivalent to 103 μM butylated hydroxytoluene). Fermentation had no effect on the antioxidant activity of PSPLABD, but the purple sweet potato and the lactic acid bacteria drink components had a synergistic effect on the inhibition of lipid peroxidation. Thus, the PSPLABD could be used as a health food which has antioxidant activity and an appealing flavor and color.

Probiotics as biotherapeutic agents: present knowledge and future prospects.

Since the early observations of Elie Metchnikoff, a wealth of experiments have described the use of selected microorganisms, mainly belonging to the lactic acid bacteria family, for the prevention or treatment of a variety of pathological situations. Nevertheless, the mechanisms underlying the proposed actions remain vastly unknown, partly as a consequence of the complexity of the gastro-intestinal ecosystem with which these biotherapeutic agents are expected to interact, but also because of the increasing variety of strains considered to have potential probiotic characteristics. During the past decades, however, the beneficial effect of specific strains in preventing or treating intestinal disorders has been substantiated by well-controlled clinical trials. Increasing evidence, including human studies, is also supporting the immunomodulatory role attributed to given lactic acid bacterial strains. The desire by consumers to use natural methods for health maintenance rather than long-term chemotherapeutic agents (i.e. antibiotics), linked to their expectation that food becomes a source of prolonged well-being, supports the speculation that the probiotic market will expand rapidly. Much of this growth will also depend on the reliability of claims that these products will bare. Therefore, the legislator will have to provide clear rules and regulations which will depend on measurable biomarkers and criteria based on scientific evidence. These commercial and legislative needs will hopefully provide scientists with the resources necessary to conduct the multidisciplinary research required to establish facts and mechanisms of action for carefully selected probiotic strains. These research results will probably be as essential for the positioning of probiotic preparations as either a food, a food supplement or as pharmaceutical preparation.

Control of Vibrio alginolyticus in Artemia culture by treatment with bacterial probiotics

In order to determine the influence of six lactic acid bacterial (LAB) strains, lactic acid and major extracellular products (ECPs) of LAB on the bacterial load of Artemia culture, two experiments were carried out. In both experiments, the dominant bacterial species were identified as Vibrio alginolyticus. The treatment with Lactobacillus brevis (1×10 8 bacteria/ml) and lactic acid (0.1 g/l) reduced the load of this bacterium in the Artemia culture water. Biochemical and morphological characteristics of the V. alginolyticus strains isolated from Artemia culture were determined. For comparative purposes, another V. alginolyticus strain isolated from diseased turbot larvae was also included. The in vitro antibacterial activity of extracellular products (ECPs) from LAB, as well as lactic acid (0.1 and 0.05 g/l), was assessed against both V. alginolyticus strains. ECPs from LAB were able to inhibit the growth of V. alginolyticus, especially those from L. brevis. In the case of lactic acid treatments, no significant inhibition of V. alginolyticus growth was observed.

Evaluation of immunomodulatory effects of lactic acid bacteria in turbot (Scophthalmus maximus).

In the present work, the effects of several lactic acid bacteria on the immune response of turbot (Scophthalmus maximus) macrophages have been studied both in vitro and in vivo. Out of six lactic acid bacterial strains tested, only heat-killed Lactococcus lactis significantly increased the turbot head kidney macrophage chemiluminescent (CL) response after 24 h of incubation. Nitric oxide (NO) was also significantly enhanced by this bacterium after 72 h of incubation with either viable (10(3) and 10(6) cells/ml) or heat-killed (10(6) cells/ml) bacteria. Viable Leuconostoc mesenteroides (10(6) cells/ml) was also capable of significantly increasing NO production. Since L. lactis proved to be the strain with more effects on the host immune function, further in vivo and in vitro experiments were conducted with this bacterium. The in vitro capacity of L. lactis to adhere to turbot intestinal mucus was positively confirmed. When orally administered, L. lactis significantly increased the macrophage CL response and the serum NO concentration after 7 days of daily administration. The antibacterial effect of the extracellular products from the six LAB strains against the fish-pathogenic bacterium Vibrio anguillarum was also demonstrated in vitro.

STUDIES ON SOME TECHNOLOGICAL PROPERTIES OF PREDOMINANT LACTIC ACID BACTERIA ISOLATED FROM NIGERIAN FERMENTED FOODS

In a programme to develop starter cultures for improving the safety and quality of traditional fermented foods in Africa, a study was conducted on lactic acid bacterial (LAB) strains isolated from the traditional selected Nigerian fermented foods kunun-zaki, wara, nono, iru. The LAB strains representing the dominating population of each product, were identified as Enterococcus faecalis (1), Pediococcus pentosaceus (4), and Lactobacillus fermentum (19). All the strains grew at 450°C, an observation which could be attributed to the tropical environment of the fermented foods. They produced a moderate spectrum of enzymes of relevance to food processing, and exhibited similar patterns of enzymatic activity between species, but generally showed weak esterase and lipase activities as compared with peptidases. While no proteinase activity was detected, most strains showed high galactosidase activity. Two strains showed ability to degrade phytic acid. None of the strains produced any detectable bacteriocins or biogenic amines under the test conditions used, and all were unable to hydrolyse bile salt. Eleven (45.8%) of the strains coagulated skim milk at 30°C within 24–36 h, and at 37°C within 12–20 h together with a moderate drop in pH. The results are discussed to highlight the relevance of technological features of starter cultures in food processing in the African environment.

The growth and interaction of yeasts and lactic acid bacteria isolated from Zimbabwean naturally fermented milk in UHT milk

Nine yeast and four lactic acid bacterial strains, previously isolated from Zimbabwean traditionally fermented milk, were inoculated into ultra-high temperature treated (UHT) milk in both single and yeast–lactic acid bacteria co-culture. The lactic acid bacteria (LAB) strains consisted of Lactococcus lactis subsp. lactis biovar. diacetylactis C1, L. lactis subsp. lactis Lc39, L. lactis subsp. lactis Lc261 and Lactobacillus paracasei subsp. paracasei Lb11. The yeast strains used were Candida kefyr 23, C. lipolytica 57, C. lusitaniae 63, C. lusitaniae 68, C. tropicalis 78, Saccharomyces cerevisiae 71, S. dairenensis 32, C. colliculosa 41 and Dekkera bruxellensis 43. After 48-h fermentation at 25°C, the samples were analysed for pH, viable yeast and bacterial counts, organic acids, volatile organic compounds (VOC) and carbon dioxide. The Lactococcus strains reduced the pH from about 6.6 to between 4.0 and 4.2, while Lb. paracasei subsp. paracasei Lb11 reduced the pH to about 5.4. Most of the yeasts, however, did not affect the final pH of the milk except for C. kefyr 23, which reduced the pH from 6.6 to 5.8. All the Lactococcus strains grew two log cycles during the 48-h fermentation period, while Lb. paracasei subsp. paracasei Lb11 grew about one log cycle. S. cerevisiae 71, C. colliculosa 41 and D. bruxellensis 43 showed poor growth in the milk in both single and co-culture. The other species of yeast grew about two log cycles. Candida colliculosa 41, S. dairenensis 32 and D. bruxellensis 43 showed reduced viability when in co-culture with Lb. paracasei subsp. paracasei Lb11. The samples in which C. kefyr 23 was used were distinct and characterised by large amounts of acetaldehyde, carbon dioxide and ethanol. However, in the samples where S. dairenensis, C. colliculosa, D. bruxellensis, C. lusitaniae, C. tropicalis, C. lipolytica and S. cerevisiae were used in co-culture, the final pH and metabolite content were mainly determined by the corresponding LAB strain. From the observations, it was concluded that C. kefyr 23 grows well in UHT milk and produces VOC that may be important to the flavour profile of the fermented milk. Enhancement of production of some flavour compounds such as acetaldehyde and malty compounds in some yeast–LAB co-cultures was presumed to be indicative of interaction between the microorganisms.

Contribution of starter culture to the sensory characteristics of fermented Almagro eggplants

Trial fermentations were performed using three experimental starter cultures with a view to selecting the most appropriate starter for use in the manufacture of Almagro eggplants. The lactic acid bacterial strains used in the starters had previously been isolated from spontaneous fermentations. The combined action of the obligate heterofermentative species Lactobacillus brevis and the facultative heterofermentative species L. plantarum yielded Almagro eggplants with sensory properties preferred by panelists. Conversely, another obligate heterofermentative species, namely, L. fermentum, present in certain starter formulations tested, appeared to encounter difficulty growing during fermentation and exerted little influence on the sensory characteristics of the eggplants produced.