Technological and safety properties of Lactobacillus plantarum strains isolated from a Tunisian traditional salted meat

A total of 17 strains of Lactobacillus plantarum, isolated from a Tunisian traditional salted meat and identified by biochemical and molecular methods, were characterized according to their technological properties including acidifying, antimicrobial and enzymatic activities as well as antibiotic resistance in order to select the most suitable for use as starter cultures for the production of fermented sausages. All the strains studied showed good acidifying activity and were able to reduce the pH to less than 4.3 in 72, 48 and 24h at 15, 25 and 37°C respectively. The majority of strains displayed antimicrobial activities against Salmonella arizonae, Staphylococcus aureus, Pseudomonas aeuroginosa and Escherichia coli, however characterization of the antimicrobial substances showed that none of the strains could produce bacteriocins. All the L. plantarum strains were able to hydrolyze casein, whereas none of them was found to possess lipolytic activity. The majority of strains of L. plantarum were resistant to tetracycline, erythromycin, rifampicin, ampicillin and penicillin G.     

Characterization and probiotic potential of Lactobacillus plantarum strains isolated from cheeses

Ninety-eight Lactobacillus plantarum strains isolated from Italian and Argentinean cheeses were evaluated for probiotic potential. After a preliminary subtractive screening based on the presence of msa and bsh genes, 27 strains were characterized. In general, the selected strains showed high resistance to lysozyme, good adaptation to simulated gastric juice, and a moderate to low bile tolerance. The capacity to agglutinate yeast cells in a mannose-specific manner, as well as the cell surface hydrophobicity was found to be variable among strains. Very high β-galactosidase activity was shown by a considerable number of the tested strains, whereas variable prebiotic utilization ability was observed. Only tetracycline resistance was observed in two highly resistant strains which harbored the tetM gene, whereas none of the strains showed β-glucuronidase activity or was capable of inhibiting pathogens. Three strains (Lp790, Lp813, and Lp998) were tested by in vivo trials. A considerable heterogeneity was found among a number of L. plantarum strains screened in this study, leading to the design of multiple cultures to cooperatively link strains showing the widest range of useful traits. Among the selected strains, Lp790, Lp813, and Lp998 showed the best probiotic potential and would be promising candidates for inclusion as starter cultures for the manufacture of probiotic fermented foods.     

Coculture-inducible bacteriocin activity of Lactobacillus plantarum strain J23 isolated from grape must

Detection and characterization of bacteriocin production by Lactobacillus plantarum strain J23, recovered from a grape must sample in Spain, have been carried out. Bacteriocin activity was degraded by proteolytic enzymes (trypsin, alfa-chymotrypsin, papaine, protease, proteinase K and acid proteases), and it was stable at high temperatures (121 degrees C, 20min), in a wide range of pH (1-12), and after treatment with organic solvents. L. plantarum J23 showed antimicrobial activity against Oenococcus oeni, and a range of Lactobacillus and Pediococcus species. Bacteriocin production was detected in liquid media only when J23 was cocultivated with some inducing bacteria, and induction took place when intact cells or 55 degrees C heated cells of the inducer were cocultivated with J23, but not with their autoclaved cells. Bacteriocin activity of J23 was not induced by high initial J23 inocula, and it was detected in cocultures during the exponential phase. The presence of ethanol or acidic pH in the media reduced bacteriocin production in the cocultures of J23 with the inducing bacteria. The presence of plantaricin-related plnEF and plnJ genes was detected by PCR and sequencing. Nevertheless, negative results were obtained for plnA, plnK, plNC8, plS and plW genes.     

Functional properties of Lactobacillus strains isolated from kimchi

The objective of this study was to evaluate the functional properties of lactic acid bacteria (LAB) from kimchi, a traditional Korean fermented vegetable product generally consumed raw as a side-dish with practically every meal.Twelve mild acid producing facultatively heterofermentative Lactobacillus strains were selected for their potential as starter cultures for fermentation of kimchi, and evaluated for their functional properties. Eleven strains were identified as Lactobacillus sakei and one as Lactobacillus plantarum. The strains identified as L. sakei differed in some physiological features; of particular interest was the fact that 9 of these strains produced L(+) lactic acid from glucose in presence of acetate.All strains were able to survive gastrointestinal conditions simulating stomach and duodenum passage. In addition, they showed higher adherence to HT-29 cells than Lactobacillus rhamnosus GG, a commercial probiotic strain used worldwide. These strains also showed antimicrobial activity against a number of food-borne pathogens. Their ability to lower cholesterol was demonstrated by BSH (bile salt hydrolytic) activity, and cholesterol assimilation tests in vitro. The results suggest the probiotic potential of these strains for use in kimchi fermentation.     

Distribution and genetic diversity of lactic acid bacteria from traditional fermented sausage

This study was conducted to investigate the distribution and genetic diversity of the native lactic acid bacteria (LAB) population in nem chua, a popular traditional Vietnamese uncooked fermented sausage. A total of 74 LAB isolates were identified and their molecular fingerprints were obtained using repetitive-PCR (rep-PCR) and pulse-field gel electrophoresis (PFGE). The results revealed that the majority of LAB isolates were Lactobacillus plantarum (67.6%), followed by Pediococcus pentosaceus (21.6%). A minority of LAB (9.5%) were Lactobacillus brevis and Lactobacillus farciminis (1.4%). A large genetic plasticity within the same species was also observed. Both rep-PCR and PFGE methods were found to be acceptable regarding reproducibility and reliability. However, this study demonstrated the higher discriminatory power of PFGE compared to rep-PCR, as observed by the higher number of clusters generated (17 and 12 clusters of L. plantarum respectively, seven and six clusters of P. pentosaceus respectively and four and two clusters of L. brevis respectively), and lower percentage of similarity among clusters in PFGE data analysis. These results also revealed that there was not a single LAB strain that was found to predominate in the product. To our knowledge, this is the first detailed analysis of the native LAB population in nem chua. As this traditional sausage is fermented naturally or only with back-slop, knowledge about the native LAB population in the product is very important to understand the microflora that has been active in fermenting the nem chua and to ensure the safety of this uncooked sausage.     

Diversity of stress tolerance in Lactobacillus plantarum, Lactobacillus pentosus and Lactobacillus paraplantarum: A multivariate screening study

Sixty-three strains of the taxonomically related species Lactobacillus plantarum subsp. plantarum, L. plantarum subsp. argentoratensis, L. paraplantarum and L. pentosus isolated from sourdoughs and other food and non-food sources and 14 strains of other members of the genus Lactobacillus were screened for their tolerance of acid, alkaline, heat, oxidative, osmotic, detergent and starvation stresses in order to evaluate the diversity of stress response. Most strains of the L. plantarum group were highly tolerant of acid, alkaline and osmotic stress and highly sensitive to detergent stress, while a larger diversity was found for other stress. Multivariate analysis allowed grouping the strains in clusters with similar response patterns. Stress response patterns in the L. plantarum group were similar to those of species of the L. casei/L. paracasei group but clearly different from those of other mesophilic Lactobacillus. No relationship was found between grouping obtained on the basis of stress response patterns and by genotypic fingerprinting (rep-PCR), nor with the taxonomic position or isolation source of the strains. Further experiments with selected strains showed that exponential phase cells were generally but not always more sensitive than stationary phase cells. The ability to grow under stressful conditions showed a slightly better correlation with the ecological conditions prevailing in the isolation niches of the strains.This study will be the basis for further investigations to identify and exploit the basis of diversity in the stress response of lactic acid bacteria.     

Production of salami from beef, horse, mutton, Blesbok (Damaliscus dorcas phillipsi) and Springbok (Antidorcas marsupialis) with bacteriocinogenic strains of Lactobacillus plantarum and Lactobacillus curvatus

Lactobacillus plantarum 423, producer of bacteriocin 423, Lactobacillus curvatus DF38, producer of curvacin DF38, and a bacteriocin-negative mutant of L. plantarum 423 (423m) were evaluated as starter cultures in the production of salami from beef, horse, mutton, Blesbok (Damaliscus dorcas phillipsi) and Springbok (Antidorcas marsupialis). Growth of L. plantarum 423 and L. curvatus DF38 was best supported in Blesbok salami, as revealed by the highest growth rate during sweating, cold smoking and maturation, and final cell numbers after 70 days (1 × 10⁸ and 5 × 10⁷ cfu/g, respectively). Growth of Listeria innocua was the best suppressed in Blesbok salami fermented with L. plantarum 423 and L. curvatus DF38. Growth of L. innocua in horse salami was best suppressed when fermented with L. curvatus DF38. The final pH of salami fermented with L. plantarum 423 and L. plantarum 423m was slightly lower (4.4) compared to the pH of salami produced with L. curvatus DF38 (pH 4.7). No significant differences (P > 0.05) were recorded by a trained sensory taste panel amongst the three starter cultures regarding colour and venison like aroma. Horse, Blesbok and Springbok salami were rated significantly higher (P ? 0.05) in salami flavour than mutton salami, which was rated the lowest for this attribute. Blesbok salami was rated the highest for sour meat aroma, while beef salami was rated the lowest. Springbok salami was rated the highest in terms of oily mouth feel. Beef salami had the most compact structure and horse salami the softest structure of all meat types fermented. In general, salami produced with L. plantarum 423 yielded the best sour meat aroma, colour, texture, venison like flavour, sour meat flavour and oily mouthfeel and is considered superior to the L. plantarum mutant (strain 423m) and L. curvatus DF38.     

Binding of mutagens to exopolysaccharide produced by Lactobacillus plantarum mutant strain 301102S

Exopolysaccharide (EPS) was produced by Lactobacillus plantarum 301102 on exposure to the mutagenic action of acridine orange and novobiocin. The biological characteristics of this mutant strain 301102S were the same as those of the parent strain, but fermented milk prepared with the mutant strain showed antimutagenic activity on 3-amino-1,4-dimethyl-5H-pyrido indole. Only EPS-bound cells of strain 301102S showed binding ability to mutagens such as heterocyclic amines, and the mutagens were inactivated by binding to EPS. The binding ability was affected by pH; the greatest percentage binding was noted at pH 8.0. Addition of Mg²⁺ and sodium dodecyl sulfate, but not oxgall, inhibited the binding ability. Therefore, the binding mechanism of the EPS may consist of ion-exchange and hydrophobic bonds, and the EPS would bind mutagens in the intestine.     

Angiotensin-converting enzyme inhibitory activity of Lactobacillus helveticus strains from traditional fermented dairy foods and antihypertensive effect of fermented milk of strain H9

Hypertension is a major global health issue which elevates the risk of a large world population to chronic life-threatening diseases. The inhibition of angiotensin-converting enzyme (ACE) is an effective target to manage essential hypertension. In this study, the fermentation properties (titratable acidity, free amino nitrogen, and fermentation time) and ACE-inhibitory (ACEI) activity of fermented milks produced by 259 Lactobacillus helveticus strains previously isolated from traditional Chinese and Mongolian fermented foods were determined. Among them, 37 strains had an ACEI activity of over 50%. The concentrations of the antihypertensive peptides, Ile-Pro-Pro and Val-Pro-Pro, were further determined by ultra performance liquid chromatography with quadrupole-time-of-flight mass spectrometry. The change of ACEI activity of the fermented milks of 3 strains exhibiting the highest ACEI activity upon gastrointestinal protease treatment was assayed. Fermented milks produced by strain H9 (IMAU60208) had the highest in vitro ACEI activity (86.4 ± 1.5%), relatively short fermentation time (7.5 h), and detectable Val-Pro-Pro (2.409 ± 0.229 µM) and Ile-Pro-Pro (1.612 ± 0.114 µM) concentrations. Compared with the control, a single oral dose of H9-fermented milk significantly attenuated the systolic, diastolic, and mean blood pressure of spontaneously hypertensive rats (SHR) by 15 to 18 mmHg during the 6 to 12 h after treatment. The long-term daily H9-fermented milk intake over 7 wk exerted significant antihypertensive effect to SHR, but not normotensive rats, and the systolic and diastolic blood pressure were significantly lower, by 12 and 10 mmHg, respectively, compared with the control receiving saline. The feeding of H9-fermented milk to SHR resulted in a significantly higher weight gain at wk 7 compared with groups receiving saline, commercial yogurt, and captopril. Our study identified a novel probiotic L. helveticus strain originated from kurut sampled from Tibet (China), which is a valuable resource for future development of functional foods for hypertension management.     

Evaluation of the functional potential of Weissella and Lactobacillus isolates obtained from Nigerian traditional fermented foods and cow's intestine

The characterisation of 24 lactic acid bacteria (LAB) isolates from Nigerian traditional fermented dairy foods, including some cow's intestine isolates, was conducted in order to select isolates for potential use as probiotics. LAB isolates were identified by partial sequencing the 16S rRNA gene as belonging to the species Lactobacillus paracasei, Lactobacillus brevis and mainly Weissella confusa. At the end of a characterisation process, 2 L. paracasei and 2 W. confusa isolates were selected, and their resistance to a simulated gastrointestinal digestion and their ability to adhere to eukaryotic cell lines were assessed. The survival to the simulated gastrointestinal passage was higher when bacterial suspensions were made in skimmed milk (2.0 ± 0.8 log units reduction) or at the simulated gastric juice pH 3 (2.7 ± 0.9 log units reduction) than at pH 2.0 (5.5 ± 0.7 log units reduction). Adhesion of LAB to both intestinal and vaginal epithelial models was comparable or higher than that of the reference Lactobacillus rhamnosus GG. However, some of the isolates increased the adhesion of the pathogen Escherichia coli LMG2092 to HT-29 and HeLa monolayers. Overall, isolates L. paracasei UI14 and W. confusa UI7 are good candidates for further studying potential benefits that support their use as probiotics. This is one of the few articles reporting the characterisation and the probiotic potential of Weissella, although more studies are needed in order to establish their safety for potential probiotic applications.     

Probiotic potential of Lactobacillus strains with anti-allergic effects from kimchi for yogurt starters

Lactobacillus strains were isolated from kimchi and investigated for their potential use for probiotic yogurt starters. Two of the isolated strains have over 90% survival rate to artificial gastric acid (pH 2.5, 1% pepsin) and artificial bile acid (0.3% oxgall). These strains were identified as Lactobacillus plantarum by 16S rRNA sequencing, and named as L. plantarum SY11 and L. plantarum SY12. The known carcinogenic enzyme, β-glucuronidase was not produced by L. plantarum SY11 and L. plantarum SY12. These 2 strains were found to be resistant to several antibiotics and strongly adhered to intestinal cells. Antiallergic effect of L. plantarum SY11 and L. plantarum SY12 was demonstrated using nitric oxide (NO) and cytokine production. L. plantarum SY11 and L. plantarum SY12 were capable of significantly decreasing NO production, and reduced T helper 2-associated cytokines, cyclooxygenase-2, tumor necrosis factor-α, and inducible nitric oxide synthase compared to control. Yogurt samples produced using L. plantarum SY11 and L. plantarum SY12 did not show significant differences in microbiological, physicochemical, and sensory properties compared with yogurt sample produced using commercial strain. Therefore, these two strains could be used as probiotic yogurt starters with antiallergic effects.     

Capsular and slime-polysaccharide production by Lactobacillus rhamnosus JAAS8 isolated from Chinese sauerkraut: Potential application in fermented milk products

Exopolysaccharides (EPSs) produced by lactic acid bacteria (LAB) play an important role in the improvement of the physical properties of fermented dairy products. To find EPS-producing LAB strains with potential industrial applications, a Lactobacillus rhamnosus strain, L. rhamnosus JAAS8, that is capable of producing two forms of EPS when grown in MRS broth or semi-defined medium with glucose as a carbon source was isolated and identified from Chinese sauerkraut. The capsular-polysaccharide (CPS) present surrounding the bacterial surface of L. rhamnosus JAAS8 was observed by both optical microscopy and transmission electron microscopy. The slime-polysaccharide (SPS) present in the growth medium was produced mainly during the exponential growth phase, while the CPS was produced only in fermentation. Monosaccharide analysis of the purified polysaccharide samples showed that the CPS was composed of galactose and N-acetylglucosamine in a molar ratio of 5:1, and the SPS was composed of galactose, glucose and N-acetylglucosamine in a molar ratio of 4:1:1. The use of L. rhamnosus JAAS8 could be considered for potential applications in the dairy industry to improve the rheological properties of fermented milk products by increasing their water-holding capacity and viscosity.     

The effect of Lactobacillus buchneri and Lactobacillus plantarum on the fermentation, aerobic stability, and ruminal degradability of low dry matter corn and sorghum silages

The effect of Lactobacillus buchneri, alone or in combination with Lactobacillus plantarum, on the fermentation, aerobic stability, and ruminal degradability of low dry matter corn and sorghum silages was studied under laboratory conditions. The inoculants were applied at 1 x 10(6) cfu/g. Silages with no additives served as control. After treatment, the chopped forages were ensiled in 1.5-L anaerobic jars. Three jars per treatment were sampled on d 2, 4, 8, 15, and 90. After 90 d of storage, the silages were subjected to an aerobic stability test lasting 5 d, in which CO2 production, as well as chemical and microbiological parameters, was measured to determine the extent of aerobic deterioration. At the end of the ensiling period (d 90), the L. buchneri- and L. buchneri + L. plantarum-inoculated silages had significantly higher levels of acetic acid than the control and L. plantarum-inoculated silages. Therefore, yeast activity was impaired in the L. buchneri- and L. buchneri + L. plantarum-inoculated silages. As a result, L. buchneri, alone or in combination with L. plantarum, improved aerobic stability of the low dry matter corn and sorghum silages. The combination of L. buchneri and L. plantarum reduced ammonia N concentrations and fermentation losses in the silages compared with L. buchneri alone. However, L. buchneri, L. plantarum, and a combination of L. buchneri + L. plantarum did not effect in situ rumen dry matter, organic matters, or neutral detergent fiber degradability of the silages. The L. buchneri was very effective in protecting the low dry matter corn and sorghum silages exposed to air under laboratory conditions. The use of L. buchneri, alone or in combination with L. plantarum, as a silage inoculant can improve the aerobic stability of low dry matter corn and sorghum silages by inhibition of yeast activity.     

Volatile compounds produced by the probiotic strain Lactobacillus plantarum NCIMB 8826 in cereal-based substrates

The production of volatile compounds by the probiotic strain, Lactobacillus plantarum NCIMB 8826, in cereal-based media (oat, wheat, barley and malt) was investigated. Sixty compounds, including fatty acids and their esters, amides, alcohols, aldehydes, aromatic hydrocarbons, furans, ketones, peroxides and pyrans, were identified. L. plantarum significantly changed the aroma profile of the four cereal broths, and each substrate showed a specific volatiles profile. Oat and barley media were the substrates more influenced by the fermentation process. The most abundant volatiles detected in oat, wheat, barley and malt were oleic acid, linoleic acid, acetic acid, and 5-hydroxymethylfurfural, respectively. Analysis of these products confirmed the heterofermentative pathway of L. plantarum. Maillard compounds were not detected during sterilisation and fermentation. This study is the first to report the volatile composition of probiotic drinks produce with non-supplemented cereal-based media and the results obtained could contribute to the development of new non-dairy probiotic formulations.     

Mixed species biofilms of Listeria monocytogenes and Lactobacillus plantarum show enhanced resistance to benzalkonium chloride and peracetic acid

We investigated the formation of single and mixed species biofilms of Listeria monocytogenes strains EGD-e and LR-991, with Lactobacillus plantarum WCFS1 as secondary species, and their resistance to the disinfectants benzalkonium chloride and peracetic acid. Modulation of growth, biofilm formation, and biofilm composition was achieved by addition of manganese sulfate and/or glucose to the BHI medium. Composition analyses of the mixed species biofilms using plate counts and fluorescence microscopy with dual fluorophores showed that mixed species biofilms were formed in BHI (total count, 8-9 log₁₀ cfu/well) and that they contained 1-2 log₁₀ cfu/well more L. monocytogenes than L. plantarum cells. Addition of manganese sulfate resulted in equal numbers of both species (total count, 8 log₁₀ cfu/well) in the mixed species biofilm, while manganese sulfate in combination with glucose, resulted in 1-2 log₁₀ more L. plantarum than L. monocytogenes cells (total count, 9 log₁₀ cfu/well). Corresponding single species biofilms of L. monocytogenes and L. plantarum contained up to 9 log₁₀ cfu/well. Subsequent disinfection treatments showed mixed species biofilms to be more resistant to treatments with the selected disinfectants. In BHI with additional manganese sulfate, both L. monocytogenes strains and L. plantarum grown in the mixed species biofilm showed less than 2 log₁₀ cfu/well inactivation after exposure for 15 min to 100 μg/ml benzalkonium chloride, while single species biofilms of both L. monocytogenes strains showed 4.5 log₁₀ cfu/well inactivation and single species biofilms of L. plantarum showed 3.3 log₁₀ cfu/well inactivation. Our results indicate that L. monocytogenes and L. plantarum mixed species biofilms can be more resistant to disinfection treatments than single species biofilms.     

Survival of human derived Lactobacillus plantarum in fermented cereal extracts during refrigerated storage

The aim of this study was to investigate the survival of a potentially probiotic Lactobacillus plantarum strain in barley, wheat and barley malt extracts. The extracts were produced from three flour/water suspensions, i.e., 5%, 20%, 30% w/w. After inoculation, the cultures were incubated for 24 h at 37 °C, and were subsequently stored at 4 °C for up to seventy days. The lactic acid and reducing sugar concentrations at the beginning of storage were significantly different between the fermented media, ranging from 0.5 g/L to 17 g/L and from 0.8 g/L to 6.5 g/L respectively, while the pH ranged between 2.9 and 3.4. It was observed that the cells survived much better in the malt extracts compared to barley and wheat extracts during refrigerated storage. Based on the results from a study using model media and supplemented cereal extracts it was derived that this was most likely due to their higher sugar concentration and the presence of protective unidentified compounds, albeit the fact that the malt extracts contained higher amounts of lactic acid.     

Lactic acid bacteria in traditional fermented Chinese foods

Food fermentation is a widely practiced and ancient technology in China. Lactic acid bacteria (LAB) are involved in many fermentation processes of Chinese traditional foods, demonstrating their profound effects on improving food quality and food safety. This review article outlines the main types of LAB fermentation as well as their typical fermented foods such as koumiss, suan-tsai, stinky tofu and Chinese sausage. The roles of LAB and the reasons for their common presence are also discussed.     

Diversity of lactic acid bacteria from Hussuwa, a traditional African fermented sorghum food

The diversity of lactic acid bacteria associated with Hussuwa fermentation, a Sudanese fermented sorghum food, was studied using a polyphasic taxonomical approach. Predominant strains could be well characterised based on a combination of phenotypic tests and genotypic methods such as ARDRA, rep-PCR and RAPD-PCR, as well as 16S rRNA gene sequencing of representative strains. Thus, the majority (128 of 220, 58.3%) of strains exhibited phenotypic properties typical of heterofermentative lactobacilli and of these, 100 strains were characterised more closely using the genotyping methods. The majority (97/100) strains could be characterised as Lactobacillus fermentum strains. Seventy-two of 220 strains (32.7%) showed phenotypic properties that are characteristic of pediococci. Of 41 selected strains investigated by genotyping techniques, 38 (92.7%) could be characterised as Pediococcus acidilactici strains, while three (7.3%) could be characterised as Pediococcus pentosaceus strains. The Hussuwa fermentation thus appears to be dominated by L. fermentum strains and P. acidilactici strains. For this reason, we selected representative and predominant strains as potential starter cultures for Hussuwa fermentation. These strains, L. fermentum strains BFE 2442 and BFE 2282 and P. acidilactici strain BFE 2300, were shown on the basis of RAPD-PCR fingerprinting to predominate in a model fermentation when used as starter cultures inoculated at 1 × 10⁶ CFU/g and to lower the pH of the fermentation to below pH 4.0 within 48 h. These cultures should be studied for further development as starter preparations in pilot scale studies in actual field fermentations.     

Antioxidant activity of prebiotic ginseng polysaccharides combined with potential probiotic Lactobacillus plantarum C88

The potential prebiotic properties of Panax ginseng polysaccharides were studied using ten strains of Lactobacillus plantarum isolated from traditional Chinese fermented foods. These probiotics showed different growth characteristics depending on the extract and strain specificity. L. plantarum C88 showed higher cell densities and growth rate when cultured on P. ginseng polysaccharides. In the in vitro antioxidant assay, P. ginseng polysaccharides combined with L. plantarum C88 were found to possess significant DPPH, ABTS and superoxide anion radicals scavenging activities, and acidic polysaccharides showed better antioxidant activity than neutral polysaccharides. Furthermore, we evaluated the antioxidant effect of acidic P. ginseng polysaccharide combined with L. plantarum C88 strain in natural ageing mice in vivo. Acidic P. ginseng polysaccharide and L. plantarum C88 together inhibited the formation of malondialdehyde (MDA) and increased the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH‐Px), catalase (CAT) and total antioxidant capacities (T‐AOC) in a dose‐dependent manner.     

Potential probiotic Lactobacillus strains from fermented sausages: Further investigations on their probiotic properties

A rational selection of probiotic microorganisms is an important challenge and requires the definition of fundamental information about the physiology and genetics of candidate strains. In this study, selected Lactobacillus (Lact.) strains already characterized in a previous study for their capability to resist low pH and to grow in conditions simulating the intestinal environment, were further investigated to explore their probiotic properties, such as the adhesion capability to intestinal human Caco-2 cell lines and their growth behaviour in the presence of various prebiotic carbohydrates. At first 25 Lactobacillus strains were characterized by pulsed field gel electrophoresis using the endonuclease NotI. Among them, 13 strains belonging to the Lact. plantarum-group were identified at species level by a multiplex PCR assay. Subsequently 11 Lactobacillus strains showing different PFGE restriction pattern and the best acid- and bile-resistances, were chosen to investigate their in vitro adhesion capability to human intestinal epithelial cells and their fermentation properties of five prebiotic substances (FOS, Inulin, IMO, GOS and lactulose) at a concentration of 2%. The 11 strains analysed in this study possessed good adhesion capability to Caco-2 cell layers and, in particular, the eight strains belonging to the Lact. plantarum-group showed the higher final number of viable adhering cells. Moreover a species-related fermentative behaviour was pointed out and the strain Lact. paracasei EL7 was the only one able to grow in the presence of all prebiotics tested. In conclusion the strains of Lactobacillus studied in this research could be further investigated to assess possible in vivo human health benefits.