Identification and probiotic potential of lactic acid bacteria from camel milk

In the present study, a total of 80 presumed lactic acid bacteria (LAB) were isolated from camel milk. Selected LAB were identified as Lactococcus lactis (cam 12), Enterococcus lactis (cam 14) and Lactobacillus plantarum (cam 15) and their potential were tested by tolerance & de-conjugation of bile salts, antimicrobial activity, surface hydrophobicity and adhesion potential) along with this of probiotics were evaluated for curd formation and assessed for sensory properties and syneresis. Selected LABs showed antimicrobial activity against wide range of pathogenic bacteria (Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus cereus and Escherchiaia. coli). LAB (cam 12, cam 14 and cam15) were highly sceptible to chloramphenicol, vancomycin, and tetracyclin. In vitro adhesion studies with Caco-2 cells demonstrated strong adhesion activity with hydrophobicity (99%) was observed. Acute oral toxicity of E. lactis and L. plantarum showed non-toxic, non-virulent and safe for industrial application. The study provides potential LAB which may act as a substitute of functional food, synthetic feed and industrial curd formulation with in the shortest span (240 min at 28–32 °C).     

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.     

Characterization of some bacteriocins produced by lactic acid bacteria isolated from fermented foods

Lactic acid bacteria (LAB) isolated from different sources (dairy products, fruits, fresh and fermented vegetables, fermented cereals) were screened for antimicrobial activity against other bacteria, including potential pathogens and food spoiling bacteria. Six strains have been shown to produce bacteriocins: Lactococcus lactis 19.3, Lactobacillus plantarum 26.1, Enterococcus durans 41.2, isolated from dairy products and Lactobacillus amylolyticus P40 and P50, and Lactobacillus oris P49, isolated from bors. Among the six bacteriocins, there were both heat stable, low molecular mass polypeptides, with a broad inhibitory spectrum, probably belonging to class II bacteriocins, and heat labile, high molecular mass proteins, with a very narrow inhibitory spectrum, most probably belonging to class III bacteriocins. A synergistic effect of some bacteriocins mixtures was observed. We can conclude that fermented foods are still important sources of new functional LAB. Among the six characterized bacteriocins, there might be some novel compounds with interesting features. Moreover, the bacteriocin-producing strains isolated in our study may find applications as protective cultures.     

Characterization of starter lactic acid bacteria from the Finnish fermented milk product viili

Aims: Phenotypic and molecular methods were used to identify and compare the strain composition of three industrial dairy starters used for the manufacture of viili. Methods and Results: Preliminary differentiation was made by phenotypic methods. Genotypic differentiation was carried out using polymerase chain reaction (PCR) and further characterization at strain level by pulsed‐field gel electrophoresis (PFGE). The isolates could be assigned as acid‐producing Lactococcus lactis strains of both lactis and cremoris subspecies, and aroma producers, identified as L. lactis subsp. lactis biovar diacetylactis and Leuconostoc mesenteroides. PCR analysis discriminated between the lactococcal subspecies, and cluster analysis of the digestion patterns of PFGE analysis revealed different genotypes in each subspecies. Each Leuconostoc‐genotype seemed to be specific to only a single starter mix. Conclusions: The work proved that in addition to L. lactis subsp. lactis biovar diacetylactis and Leuc. mesenteroides subsp. cremoris, commercial viili starters of traditional origin may contain (i) only L. lactis subsp. cremoris, (ii) both L. lactis subsp. cremoris and L. lactis subsp. lactis as a minority, and – as a new discovery – (iii) only L. lactis subsp. lactis. Significance and Impact of the Study: The results obtained give an overview of the microbial population of viili starters and can be exploited in the development of optimized starter cultures for industrial‐scale manufacture of viili.     

Characterization and antimicrobial spectrum of bacteriocins produced by lactic acid bacteria isolated from traditional Bulgarian dairy products

Aims:  To isolate bacteriocin-producing lactic acid bacteria (LAB) with high wide spectrum antibacterial activity and to characterize their inhibitory peptides.
Method and Results:  Seven LAB strains [ Lactobacillus casei ssp. rhamnosus (PC5), Lactobacillus delbrueckii ssp. bulgaricus (BB18), Lactococcus lactis ssp. lactis (BCM5, BK15), Enterococcus faecium (MH3), Lactobacillus plantarum (BR12), Lactobacillus casei ssp. casei (BCZ2)], isolated from authentic Bulgarian dairy products were capable of producing bacteriocins, inhibiting the widest range of pathogenic bacteria. The bacteriocins were resistant to heating at 121°C for 15 min, stable at pH 2–10, sensitive to protease, insensitive to α-amylase and lipase. Two of bacteriocins produced by Lact. bulgaricus BB18 (bulgaricin BB18) and E. faecium MH3 (enterocin MH3) were purified and the molecular masses were determined. The N -terminal amino acid sequence of bulgaricin BB18 did not show strong homology to other known bacteriocins.
Conclusions:  Lactobacillus bulgaricus BB18 and E. faecium MH3 produce two novel bacteriocins highly similar to the pediocin-like nonlantibiotics.
Significance and Impact of the Study:  The two bacteriocins are potential antimicrobial agents and, in conjunction with their producers, may have use in applications to contribute a positive effect on the balance of intestinal microflora. Furthermore, bulgaricin BB18 strongly inhibits Helicobacter pylori .     

An analysis of bacteriocins produced by lactic acid bacteria isolated from malted barley

AIMS: The aim of this study was to perform a detailed characterization of bacteriocins produced by lactic acid bacteria (LAB) isolated from malted barley. METHODS AND RESULTS: Bacteriocin activities produced by eight LAB, isolated from various types of malted barley, were purified to homogeneity by ammonium sulphate precipitation, cation exchange, hydrophobic interaction and reverse-phase liquid chromatography. Molecular mass analysis and N-terminal amino acid sequencing of the purified bacteriocins showed that four non-identical Lactobacillus sakei strains produced sakacin P, while four Leuconostoc mesenteroides strains were shown to produce bacteriocins highly similar or identical to leucocin A, leucocin C or mesenterocin Y105. Two of these bacteriocin-producing strains, Lb. sakei 5 and Leuc. mesenteroides 6, were shown to produce more than one bacteriocin. Lactobacillus sakei 5 produced sakacin P as well as two novel bacteriocins, which were termed sakacin 5X and sakacin 5T. The inhibitory spectrum of each purified bacteriocin was analysed and demonstrated that sakacin 5X was capable of inhibiting the widest range of beer spoilage organisms. CONCLUSION: All bacteriocins purified in this study were class II bacteriocins. Two of the bacteriocins have not been described previously in the literature while the remaining purified bacteriocins have been isolated from environments other than malted barley. SIGNIFICANCE AND IMPACT OF THE STUDY: This study represents a thorough analysis of bacteriocin-producing LAB from malt and demonstrates, for the first time, the variety of previously identified and novel inhibitory peptides produced by isolates from this environment. It also highlights the potential of these LAB cultures to be used as biological controlling agents in the brewing industry.     

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.

     

Identification and characterization of the dominant lactic acid bacteria isolated from traditional fermented milk in Mongolia

Five samples of Airag and 20 of Tarag (both in Mongolia) were collected from scattered households. One hundred strains of lactic acid bacteria (LAB) were isolated and identified from these samples according to phenotypic characterization and 16S rRNA gene sequence analysis. Eighty-five isolates belonged to the genus Lactobacillus, 15 being classified as coccoid LAB. All isolates belonged to 5 genera and 11 to different species and subspecies. Lactobacillus (Lb.) helveticus was predominant population in Airag samples, Lb. fermentum and Lb. helveticus were the major LAB microflora in Tarag.     

Characterization of lactic acid bacteria isolated from sourdoughs for Cornetto, a traditional bread produced in Basilicata (Southern Italy)

A total of 41 strains of lactic acid bacteria (LAB) isolated from durum wheat sourdoughs used to produce Cornetto di Matera bread, were identified by SDS-PAGE of whole cell proteins (WCP) and screened for acid production ability, antimicrobial activity and exopolysaccharide (EPS) production. The isolates were identified as Lactobacillus plantarum (49%), Leuconostoc mesenteroides (17%), Lactobacillus curvatus (15%), Lactobacillus paraplantarum (12%), Weissella cibaria (5%) and Lactobacillus pentosus (2%). Several strains of Lb. plantarum and Leuc. mesenteroides showed a high acid production ability. The antagonistic activity was tested using an agar-spot deferred antagonism assay against a set of five indicators. The species had different profiles of inhibition. Lb. plantarum had the largest spectrum of inhibition, while no isolates of W. cibaria and Leuc. mesenteroides showed antimicrobial activity. No strains had antimicrobial activity against Bacillus cereus. The inhibitory activity of five strains was confirmed to be sensitive to proteolytic enzymes and thus potentially due to bacteriocin production. All Leuc. mesenteroides and W. cibaria strains produced EPS from sucrose. Some Lb. plantarum and Lb. paraplantarum strains produced EPS from different sugars in solid media. EPS production in liquid media was different within the species, with the highest production in liquid media containing glucose and maltose. A defined strain starter culture (W. cibaria DBPZ1006, Lb. plantarum DBPZ1015 and S. cerevisiae MTG10) was selected on the basis of technological properties and tested in model sourdough fermentations.     

Purification and characterization of two bacteriocins produced by lactic acid bacteria isolated from Mongolian airag

AIMS: The aim of this study was to isolate and identify bacteriocin-producing lactic acid bacteria (LAB) issued from Mongolian airag (traditional fermented mare's milk), and to purify and characterize bacteriocins produced by these LAB. METHODS AND RESULTS: Identification of the bacteria (Enterococcus durans) was carried out on the basis of its morphological, biochemical characteristics and carbohydrate fermentation profile and by API50CH kit and 16S rDNA analyses. The pH-neutral cell-free supernatant of this bacterium inhibited the growth of several Lactobacillus spp. and food-borne pathogens including Escherichia coli, Staphylococcus aureus and Listeria innocua. The antimicrobial agent (enterocin A5-11) was heat stable and was not sensitive to acid and alkaline conditions (pH 2-10), but was sensitive to several proteolytic enzymes. Its inhibitory activity was completely eliminated after treatment with proteinase K and alpha-chymotrypsin. The activity was however not completely inactivated by other proteases including trypsin and pepsin. Three-step purification procedure with high recovery yields was developed to separate two bacteriocins. The applied procedure allowed the recovery of 16% and 64% of enterocins A5-11A and A5-11B, respectively, present in the culture supernatant with purity higher than 99%. SDS-PAGE analyses revealed that enterocin A5-11 has a molecular mass of 5000 Da and mass spectrometry analyses demonstrates molecular masses of 5206 and 5218 Da for fractions A and B, respectively. Amino acid analyses of both enterocins indicated significant quantitative difference in their contents in threonine, alanine, isoleucine and leucine. Their N-termini were blocked hampering straightforward Edman degradation. CONCLUSIONS: Bacteriocins A5-11A and B from Ent. durans belong to the class II of bacteriocins. SIGNIFICANCE AND IMPACT OF THE STUDY: Judging from molecular masses, amino acid composition and spectrum of activities, bacteriocins A5-11A and B from Ent. durans show high degree of similarity with enterocins L50A and L50B isolated from Enterococcus faecium (Cintas et al. 1998, 2000) and with enterocin I produced by Ent. faecium 6T1a, a strain originally isolated from a Spanish-style green olive fermentation (Floriano et al. 1998).     

Dominant lactic acid bacteria and their technological properties isolated from the Himalayan ethnic fermented milk products

Ethnic people of the Himalayan regions of India, Nepal, Bhutan and China consume a variety of indigenous fermented milk products made from cows milk as well as yaks milk. These lesser-known ethnic fermented foods are dahi, mohi, chhurpi, somar, philu and shyow. The population of lactic acid bacteria (LAB) ranged from 10(7) to 10(8) cfu/g in these Himalayan milk products. A total of 128 isolates of LAB were isolated from 58 samples of ethnic fermented milk products collected from different places of India, Nepal and Bhutan. Based on phenotypic characterization including API sugar test, the dominant lactic acid bacteria were identified as Lactobacillus bifermentans, Lactobacillus paracasei subsp. pseudoplantarum, Lactobacillus kefir, Lactobacillus hilgardii, Lactobacillus alimentarius, Lactobacillus paracasei subsp. paracasei, Lactobacillus plantarum, Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris and Enterococcus faecium. LAB produced a wide spectrum of enzymes and showed high galactosidase, leucine-arylamidase and phosphatase activities. They showed antagonistic properties against selected Gram-negative bacteria. None of the strains produced bacteriocin and biogenic amines under the test conditions used. Most strains of LAB coagulated skim milk with a moderate drop in pH. Some strains of LAB showed a high degree of hydrophobicity, suggesting these strains may have useful adhesive potential. This paper is the first report on functional lactic acid bacterial composition in some lesser-known ethnic fermented milk products of the Himalayas.     

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.     

Exocellular polysaccharides produced by lactic acid bacteria

Abstract The production of homopolysaccharides (dextrans, mutans) and heteropolysaccharides by lactic acid bacteria, their chemical composition, their structure and their synthesis are outlined. Mutans streptococci, which include Streptococcus mutans and S. sobrinus produce soluble and insoluble α-glucans. The latter may contain as much as 90%α-1–3 linkages and possess a marked ability to promote adherence to the smooth tooth surface causing dental plaque. Dextrans produced by Leuconostoc mesenteroides are high molecular weight α-glucans having 1–6, 1–4 and 1–3 linkages, varying from slightly to highly branched; 1–6 linkages are predominant. Emphasis is put on exopolysaccharide producing thermophilic and mesophilic lactic acid bacteria, which are important in the dairy industry. The produced polymers play a key role in the rheological behaviour and the texture of fermented milks. One of the main problems in this field is the transitory nature of the thickening trait. This instability is not yet completely understood. Controversial results exist on the sugar composition of the slime produced, but galactose and glucose have always been identified with galactose predominating in most cases.     

Phenotypic diversity of lactic acid bacteria isolated from fermented sausages produced in Basilicata (Southern Italy)

AIMS: to evaluate the evolution of lactic acid bacteria (LAB) populations in traditional fermented sausages (salsiccia and soppressata) produced in artisanal and industrial plants in Basilicata (Southern Italy). METHODS AND RESULTS: Four hundred and fourteen lactic acid bacteria (LAB) cultures were isolated from samples of sausages at different stages of ripening. A phenotypic characterization of the isolates was carried out using a set of 28 tests, and 34 clusters were identified at the 80% similarity level using hierarchical cluster analysis. Of the isolates 50% were identified as Lactobacillus sakei (with several biotypes), 22% as Pediococcus spp. (mainly Ped. pentosaceus), 7% as Leuconostoc (Leuc. carnosum, Leuc. gelidum, Leuc. pseudomesenteroides), 6% as Lact. plantarum, 1% as Lact. curvatus. Other lactobacilli, including unidentified species, were present in lower numbers. CONCLUSION: The phenotypic diversity and composition of the LAB flora varied as a function of the production plant, product type and ripening time. SIGNIFICANCE AND IMPACT OT THE STUDY: A new procedure based on bootstrapping and Multidimensional Scaling was successfully used to obtain a graphical representation of the evolution of the LAB populations.     

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.