Cupuassu juice fermentation by Lactiplantibacillus plantarum Lp62 produces an antioxidant enriched probiotic beverage.

The present work aimed to produce a cupuassu juice (Theobroma grandiflorum) fermented by the probiotic bacterium Lactiplantibacillus plantarum Lp62 and to analyze its antioxidant potential, antimicrobial activity, and resistance to biological barriers. The fermented beverage showed an increase in the content of phenolics, flavonoids, and antioxidant potential. The culture showed antagonistic activity against pathogens, but this result was not observed when the juice was tested. The probiotic strain remained viable under refrigeration, even in an acidified environment, and survived simulated gastrointestinal transit in vitro. L. plantarum Lp62 showed 30% adherence to HT-29 intestinal cells and proved to be safe in terms of antibiotic resistance and production of virulence factors. Fermentation increased the functional characteristics of cupuassu juice. This drink proved to be a good vehicle for the delivery of the probiotic bacteria L. plantarum Lp62.

Inhibition of a spoilage exopolysaccharide producer by bioprotective extracts from Lactobacillus acidophilus CRL641 and Latilactobacillus curvatus CRL705 in vacuum-packaged refrigerated meat discs.

The effect of bioprotective extracts (BEs) from Lactobacillus acidophilus CRL641 (BE-1) and Latilactobacillus curvatus CRL705 (BE-2) against the exopolysaccharide producer Latilactobacillus sakei CRL1407 in vacuum-packaged meat discs at 4 °C was evaluated. Lat. sakei CRL1407 was able to grow in control samples from 2.80 to 7.77 log CFU/g after 38 days. BE-1 and BE-2 reduced bacterial growth by 2.11 and 1.35 log CFU/g, respectively, but their combination led to a greater growth reduction (3.31 log CFU/g). The antimicrobial activity was detected in treated samples with BE-1 and BE-1 + BE-2 until day 16, while with BE-2 only at the initial time. The pH values remained constant in the discs treated with the BEs combination, whereas the greatest drop in pH was observed in control samples. The minor lipid oxidation without perceptible color changes was detected in the presence of BE-1 and BE-1 + BE-2. The combination of BEs as biocontrol agent plus conventional preservation barriers could extend the fresh meat shelf-life without quality loss.

Bioprotective extracts from Lactobacillus acidophilus CRL641 and Latilactobacillus curvatus CRL705 inhibit a spoilage exopolysaccharide producer in a refrigerated meat system.

The effect of bioprotective extracts (BEs) from Latilactobacillus curvatus CRL705 and Lactobacillus acidophilus CRL641 against Latilactobacillus sakei CRL1407 was evaluated in a refrigerated meat model system under vacuum and aerobic conditions at 4 and 10 °C. As shown by culturing, the BE-1 from L. acidophilus completely inhibited the spoilage strain, while that from Lat. Curvatus CRL705 (BE-2) and its combination with BE-1 exerted a bacteriostatic effect. The antimicrobial activity and exopolysaccharide production correlated with the efficacy of inhibitory treatment while final pH decrease was higher in control samples. When flow cytometry was applied, a lack of correlation with plate counting was found; counts under the detection limit for BE-1 at 21 and 28 days at 4 and 10 °C represented between 64.15 and 73.70% of dead cells. Thus, the concurrence of lactic acid bacteria as biocontrol agents and the use of more accurate tools to prevent the growth of deteriorating species will contribute to the extension of fresh meat shelf-life without quality loss.

Inactivation kinetics of beer spoilage bacteria (Lactobacillus brevis, Lactobacillus casei, and Pediococcus damnosus) during acid washing of brewing yeast.

This work aimed to estimate the inactivation kinetic parameters of four potential beer spoilage bacteria (Lactobacillus brevis DSM 6235, Lactobacillus casei ATCC 334, Pediococcus damnosus DSM 20289 and Pediococcus damnosus ATCC 29358) inoculated in brewing yeast submitted to acid washing with purposes of yeast recycle. The experiments were conducted at 4 °C in solutions with pH 1.5, pH 2, and pH 3 adjusted employing 85% phosphoric acid. The acid washing treatment of brewing yeasts in the most common pH used (pH 2.0) demanded almost 50 min for the first decimal reduction (δ) of L. brevis DSM 6235. Sensible strains to acid washing such as P. damnosus DSM 20289 demanded almost 70 min for 4 log reductions to be achieved. On the other hand, pH reduction of the acid washing from 2.0 to 1.5 allowed 4 log reduction of L. brevis DSM 6235) to be obtained in less than 50 min, without ruining brewer's yeast viability. Acid washing in pH 1.5 is a viable method for the inactivation of bacterial contaminants of brewing yeasts. Recycling of brewing yeasts through this approach may contribute to a more sustainable and environmental-friendly industry.

Curcumin-mediated antimicrobial photodynamic therapy reduces the viability and vitality of infected dentin caries microcosms.

BACKGROUND: To our knowledge, there is a lack of evidence on the effect of Antimicrobial Photodynamic Therapy (aPDT) by the application of curcumin against complex biofilms of dental caries lesions. This study aimed to evaluate the viability, vitality, and acid metabolism of infected dentin caries microcosms treated with curcumin-mediated aPDT. METHODS: After microcosm biofilms growing anaerobically on bovine dentin disks immersed in McBain medium with 1% sucrose at 37 °C for 5 days, the biofilms were treated by the association of DMSO water solution or 600 µmol L-1 curcumin with 0, 37.5 or 75 J cm-2 blue LED (455 nm). Then, the colony-forming units (CFU) counts of total microorganisms, total streptococci, mutans streptococci, and total lactobacilli were determined by plating. The lactic acid concentration was analyzed by enzymatic spectrophotometry method, while the vitality of intact biofilms was evaluated by confocal laser scanning microscope (CLSM). Statistical analysis was performed by Kruskal Wallis and post-hoc Dunn's tests (P < 0.05). RESULTS: Curcumin alone did not affect the viability of microorganisms and the vitality of intact biofilms. However, 75 J cm-2 LED alone decreased the total microorganisms and total lactobacilli counts. The combination of curcumin and LED reduced significantly the counts of all microorganism groups and the vitality of intact biofilms. Differences were not observed between the lactic acid concentrations of distinct groups. CONCLUSIONS: Therefore, curcumin-mediated aPDT was effective in reducing the viability and the vitality of infected dentin caries microcosms, without interfering in their acidogenicity.

Purification and characterization of two new cell-bound bioactive compounds produced by wild Lactococcus lactis strain.

Novel compounds and innovative methods are required considering that antibiotic resistance has reached a crisis point. In the study, two cell-bound antimicrobial compounds produced by Lactococcus lactis ID1.5 were isolated and partially characterized. Following purification by cationic exchange and a solid-phase C18 column, antimicrobial activity was recovered after three runs of RPC using 60% (v/v) and 100% (v/v) of 2-propanol for elution, suggesting that more than one antimicrobial compound were produced by L. lactis ID1.5, which were in this study called compounds AI and AII. The mass spectrum of AI and AII showed major intensity ions at m/z 1070.05 and 955.9 Da, respectively. The compound AI showed a spectrum of antimicrobial activity mainly against L. lactis species, while the organisms most sensitive to compound AII were Bacillus subtilis, Listeria innocua, Streptococcus pneumoniae and Pseudomonas aeruginosa. The antimicrobial activity of both compounds was suppressed by treatment with Tween 80. Nevertheless, both compounds showed high stability to heat and proteases treatments. The isolated compounds, AI and AII, showed distinct properties from other antimicrobial substances already reported as produced by L. lactis, and have a significant inhibitory effect against two clinically important respiratory pathogens.

Impact of NaCl reduction on lactic acid bacteria during fermentation of Nocellara del Belice table olives.

Table olives are widely consumed worldwide but, due to the presence of NaCl in fermenting brines, they contain high levels of sodium. A promising strategy to lower sodium content is the reduction or substitution of NaCl in brines with other chlorides. However, these procedures may impact safety, spoilage, as well as quality and technological properties, including the evolution and final composition of the fermenting microbiota. In the present work the effects of partially replacing NaCl with KCl in fermenting brines on the microbiological quality of Nocellara del Belice olives produced by Spanish style (Sivigliano) or Castelvetrano methods have been analyzed. In both cases, the fermentation steps were performed in parallel, in brines containing either NaCl alone, or partially replaced with different proportions of KCl (25, 50 and 75%), while maintaining a final saline concentration of 9% (Sivigliano method) or 7% (Castelvetrano). To compare microbial dynamics in the experimental brines, changes in bacterial ecology were monitored during fermentation with a polyphasic approach, including both microbiological methods and culture-independent techniques based on DGGE and NGS analysis. The main microbial groups detected in the olive microbiota from both production procedures were LAB and yeasts. Overall, the data demonstrate that partial replacement of NaCl with KCl does not increase the risk of contamination, nor the overgrowth of pathogens or spoiler microbes.

Assessment of the in vitro bioactive properties of lactic acid bacteria isolated from native ecological niches of Ecuador.

Lactic acid bacteria are known for their biotechnological potential. In various regions of Ecuador numerous indigenous biological resources are largely undocumented. In this study, we evaluated the potential probiotic characteristics and antagonistic in vitro properties of some lactic acid bacteria from native niches of the subtropical rain forests of Ecuador. These isolates were identified according to their morphological properties, standard API50CH fermentation profile and RAPD-DNA polymorphism pattern. The selected isolates were further evaluated for their probiotic potential. The isolates grew at 15°C and 45°C, survived at a pH ranging from 2.5 to 4.5 in the presence of 0.3% bile (>90%) and grew under sodium chloride conditions. All selected isolates were sensitive to ampicillin, amoxicillin and cefuroxime and some showed resistance to gentamicin, kanamycin and tetracycline. Moreover, the agar well diffusion assay showed that the supernatant of each strain at pH 3.0 and pH 4.0, but not at pH 7.0 exhibited increased antimicrobial activity (inhibition zone >15mm) against two foodborne pathogens, Escherichia coli and Salmonella spp. To our knowledge, this is the first report describing the antagonistic activity against two foodborne pathogens and the probiotic in vitro potential of lactic acid bacteria isolated from native biota of Ecuador.

Selection of autochthonous lactic acid bacteria from goat dairies and their addition to evaluate the inhibition of Salmonella typhi in artisanal cheese.

This study aimed to select autochthonous lactic acid bacteria (LAB) with probiotic and functional properties from goat dairies and test their addition to artisanal cheese for the inhibition of Salmonella typhi. In vitro tests, including survival in the gastrointestinal tract (GIT), auto- and co-aggregation, the hemolytic test, DNase activity, antimicrobial susceptibility, antibacterial activity, tolerance to NaCl and exopolysaccharide (EPS), gas and diacetyl production were conducted for sixty isolates. Based on these tests, four LAB isolates (UNIVASF CAP 16, 45, 84 and 279) were selected and identified. Additional tests, such as production of lactic and citric acids by UNIVASF CAP isolates were performed in addition to assays of bile salt hydrolase (BSH), ß-galactosidase and decarboxylase activity. The four selected LAB produced high lactic acid (>17 g/L) and low citric acid (0.2 g/L) concentrations. All selected strains showed BSH and ß-galactosidase activity and none showed decarboxylase activity. Three goat cheeses (1, 2 and control) were produced and evaluated for the inhibitory action of selected LAB against Salmonella typhi. The cheese inoculated with LAB (cheese 2) decreased 0.38 log10 CFU/g of S. Typhy population while in the cheese without LAB inoculation (cheese 1) the pathogen population increased by 0.29 log units. Further, the pH value increased linearly over time, by 0.004 units per day in cheese 1. In the cheese 2, the pH value decreased linearly over time, by 0.066 units per day. The cocktail containing selected Lactobacillus strains with potential probiotic and technological properties showed antibacterial activity against S. typhi in vitro and in artisanal goat cheese. Thus, goat milk is important source of potential probiotic LAB which may be used to inhibit the growth of Salmonella population in cheese goat, contributing to safety and functional value of the product.

Probiotic properties of lactic acid bacteria isolated from water-buffalo mozzarella cheese.

This study evaluated the probiotic properties (stability at different pH values and bile salt concentration, auto-aggregation and co-aggregation, survival in the presence of antibiotics and commercial drugs, study of ß-galactosidase production, evaluation of the presence of genes encoding MapA and Mub adhesion proteins and EF-Tu elongation factor, and the presence of genes encoding virulence factor) of four LAB strains (Lactobacillus casei SJRP35, Leuconostoc citreum SJRP44, Lactobacillus delbrueckii subsp. bulgaricus SJRP57 and Leuconostoc mesenteroides subsp. mesenteroides SJRP58) which produced antimicrobial substances (antimicrobial peptides). The strains survived the simulated GIT modeled in MRS broth, whole and skim milk. In addition, auto-aggregation and the cell surface hydrophobicity of all strains were high, and various degrees of co-aggregation were observed with indicator strains. All strains presented low resistance to several antibiotics and survived in the presence of commercial drugs. Only the strain SJRP44 did not produce the ß-galactosidase enzyme. Moreover, the strain SJRP57 did not show the presence of any genes encoding virulence factors; however, the strain SJRP35 presented vancomycin resistance and adhesion of collagen genes, the strain SJRP44 harbored the ornithine decarboxylase gene and the strain SJRP58 generated positive results for aggregation substance and histidine decarboxylase genes. In conclusion, the strain SJRP57 was considered the best candidate as probiotic cultures for further in vivo studies and functional food products development.

Lactic acid bacteria from raw milk as potentially beneficial strains to prevent bovine mastitis.

Bovine mastitis produces a wide variety of problems in the dairy farm. The treatment of this disease is based on the use of antibiotics which are not always effective. These drugs are also responsible for the presence of residues in the milk and the increase of antibiotic-resistant strains. Probiotic products were proposed as a valid alternative to antibiotic therapies and are also useful for the prevention of infectious syndromes. With the aim of designing a probiotic product to prevent bovine mastitis, lactic acid bacteria (LAB) were isolated from foremilk samples from different dairy farms in Córdoba-Argentina. One hundred and seventeen LAB were isolated and their beneficial characteristics such as the production of inhibitory substances, surface properties and production of exopolysaccharides (EPS) were assessed. Most of them displayed low degree of hydrophobicity, autoaggregation, EPS negative phenotype and were identified as Enterococcus hirae and Pediococcus pentosaceus. Nine LAB strains inhibited three indicator bacteria. Some isolates were pre-selected and genetically identified according to the results obtained. Antibiotic resistance and virulence factors were studied for the assessment of the safety of the strains. The results obtained were compared to those reported previously from samples obtained in the North-western area of the country and some differences were found.

Use of Carnobacterium maltaromaticum cultures and hydroalcoholic extract of Lippia sidoides Cham. against Listeria monocytogenes in fish model systems.

Minimally processed refrigerated ready-to-eat fishes may offer health risk of severe infection to susceptible individuals due to contamination by the psychrotolerant bacterium L. monocytogenes. In this work, inhibition of L. monocytogenes by a plant extract and lactic acid bacteria (LAB) was studied in model fish systems kept at 5 °C for 35 days. For that, fillets of tropical fish "surubim" (Pseudoplatystoma sp.) and hydroalcoholic extract of the plant Lippia sidoides Cham. ("alecrim pimenta") were used. Fish peptone broth (FPB), "surubim" broth and "surubim" homogenate were inoculated with combinations of L. monocytogenes and bacteriocin-producing Carnobacterium maltaromaticum (C2 and A9b(+)) and non bacteriocin-producing C. maltaromaticum (A9b(-)), in the presence or absence of extract of "alecrim pimenta" (EAP). In all model systems, monocultures of L. monocytogenes and carnobacteria reached final populations ≥10(8) CFU/ml after 35 days, except for L. monocytogenes in "surubim" homogenate (10(4) CFU/ml). In FPB, EAP alone and combined with cultures of LAB inhibited L. monocytogenes but carnobacteria without EAP were only weakly antilisterial. In "surubim" broth, EAP alone did not prevent L. monocytogenes growth but cultures of carnobacteria combined or not with EAP inhibited L. monocytogenes, with more pronounced effect being observed for C. maltaromaticum C2, which produced bacteriocin. In "surubim" homogenate, EAP alone and combined with cultures of C. maltaromaticum A9b(-) and A9b(+) were strongly inhibitory to L. monocytogenes, while C. maltaromaticum C2 with EAP caused transient inhibition of L. monocytogenes. No significant inhibition of L. monocytogenes was observed for carnobacteria in "surubim" homogenate without EAP. In conclusion, it was observed that the use of EAP and cultures of carnobacteria have potential to inhibit L. monocytogenes in fish systems and the applications should be carefully studied, considering the influence of food matrix.

Effect of sucrose on the selection of mutans streptococci and lactobacilli in dental biofilm formedin situ.

Microorganisms are selected in dental biofilm by the acidic environment created by sugar fermentation, but the effect of extracellular polysaccharide (EPS) on the counts of cariogenic bacteria is not clear. Dental biofilm was formed in situ for 13 days under exposure 8 times a day to distilled-deionized water, glucose + fructose or sucrose solutions. Mutans streptococci (MS) counts were not different among the groups, but lactobacilli (LB) were significantly higher in glucose + fructose and sucrose groups, without significant difference between them, irrespective of the higher insoluble EPS concentration in the sucrose biofilm matrix. The data suggest that exposure to sugar is more relevant for the predominance of LB in dental biofilm than for MS and that insoluble EPS does not change the counts of these microorganisms in the biofilm.

Influence of ethanol and low pH on arginine and citrulline metabolism in lactic acid bacteria from wine.

The aim of this work was to study the effects of ethanol on cell growth and arginine and citrulline metabolism in two heterofermentative lactic acid bacteria from wine, and to determine their possible association with the formation of ethyl carbamate (EC), a carcinogenic compound. Lactobacillus hilgardii X1B is able to utilize arginine and citrulline, while Oenococcus oeni m can only use citrulline, a precursor of EC. Growth of both microorganisms was partially inhibited by 10 and 15% (v/v) ethanol. Specific arginine consumption by L. hilgardii increased when the pH value diminished from 6.5 to 3.8, but was not affected by an increasing ethanol concentration. However, the ethanol concentration affected the specific citrulline consumption of both microorganisms. Arginine metabolism by L. hilgardii X1B increased the amount of citrulline, thus allowing production of EC in the medium. Citrulline utilization by both microorganisms, at all pH values studied, indirectly inhibited the formation of EC; indeed, one of the precursors had practically disappeared after 48 h of incubation. Due to its ability to form precursors, L. hilgardii X1B has the potential to contribute to EC formation, whereas citrulline utilization by O. oeni m in the presence of ethanol may contribute to diminishing the formation of EC. Rapid degradation of citrulline in the presence of ethanol by O. oeni m is important from a toxicological point of view, because it is important to keep the EC levels as low as possible.