Organic acid produced by lactic acid bacteria from bekasam as food biopreservatives

Lactic acid bacteria (LAB) are a representative probiotic. As the dominant flora in the human intestinal tract, LAB can regulate the balance of human intestinal flora and improve host health. The purpose of this study was to isolate and screen LAB that are well suited to the intestinal characteristics of the Chinese population, with excellent probiotics and high antibacterial activity. After 16S ribosomal RNA (rRNA) homology and phylogenetic tree analysis, potential probiotics were tested for their antibacterial activity, resistance to artificial gastrointestinal fluid and drugs, surface hydrophobicity, and safety. Three strains of LAB with acid resistance, bile salt resistance, epithelial cell adhesion, and no multidrug resistance were selected: Lactobacillus salivarius, Leuconostoc lactis, and Lactobacillus paracasei. Analysis of the antibacterial active substances in the three strains and their fermentation broths revealed that the main antibacterial substances of L. lactis were organic acids, whereas those of L. salivarius and L. paracasei were organic acids and bacteriocins with broad-spectrum antibacterial activity. These three strains of probiotic LAB with high antibacterial activity were identified as bacterial resources that could potentially be used to develop probiotic preparations for the prevention and treatment of intestinal diseases caused by intestinal pathogens.

Interest in obtaining bacteriocin-producing strains of lactic acid bacteria (LAB) from different sources has been increasing in recent years due to their multiple applications in health and food industries. This study focused on the isolation and characterization of metabolically active populations of bacteriocinogenic LAB and the evaluation of their antimicrobial substances as well as of some nutritional requirements of them. One hundred and fifty colonies of LAB from artisanal cheeses produced in Minas Gerais state (Brazil) were isolated and screened for their antimicrobial activity. According to their activity against Listeria monocytogenes, ten strains were selected and subsequently identified using biochemical and molecular techniques including 16s rRNA amplification and sequencing as Enterococcus faecalis, Lactobacillus spp., and Pediococcus pentosaceus. Antimicrobial substances produced by four of the selected strains, P. pentosaceus 63, P. pentosaceus 145, P. pentosaceus 146, and P. pentosaceus 147, were biochemically characterized, and presented sensitivity to proteolytic enzymes (suggesting their proteinaceous nature) and to extreme pH. Antimicrobial activity showed stability after treatment with lipase, catalase, α-amylase, and chemicals. Growth kinetics of the P. pentosaceus selected showed maximal bacteriocin production at 37 °C during the end of the exponential growth phase (25,600 AU/mL) and stable production during 24 h of incubation. Dextrose, maltose, and a mixture of peptone, meat extract, and yeast extract increased bacteriocin production. This study demonstrated that dairy products provide a good alternative for obtaining LAB, with the ability to produce antimicrobial substances such as bacteriocins that have potential use as biopreservatives in food.

The discarding of wastes into the environment is a significant problem for many communities. Still, food waste can be used for lactic acid bacteria (LAB) growth. Here, we evaluated three growth media equivalent to de Mann Rogosa Sharpe (MRS), using apple bagasse, yeast waste, fish flour, forage oats, and cheese whey. Cell-free supernatants of eight LAB strains were tested for antimicrobial activity against nine indicator microorganisms. The supernatants were also evaluated for protein content, reducing sugars, pH, and lactic acid concentration. Cell-free supernatants from fish flour broth (FFB) LAB growth were the most effective. The strain Leuconostoc mesenteroides PIM5 presented the best activity in all media. L. mesenteroides CAL14 completely inhibited L. monocytogenes and strongly inhibited Bacillus cereus (91.1%). The strain L. mesenteroides PIM5 consumed more proteins (77.42%) and reducing sugars (56.08%) in FFB than in MRS broth (51.78% and 30.58%, respectively). Culture media formulated with agroindustrial wastes positively improved the antimicrobial activity of selected LAB, probably due to the production of antimicrobial peptides or bacteriocins.

The Cassava and Ogi effluents include substantial quantities of bacteria, particularly lactic acid (LABs), which has garnered much attention as probiotics to improve human health. The potential desirable characteristics of the LAB as a probiotic have necessitated the screening of various fermentative compounds to identify a good source of LAB for probiotic use. This was designed to evaluate the probiotic activities of 10 Lactic Acid Bacteria (LAB) strains previously isolated from Cassava and Ogi effluents. Probiotic activities, including pH, titratable acidity, bile salt tolerance, and safety (DNase, hemolysis, and antibacterial activity) were examined using standard laboratory techniques. The pH and total titratable acidity (TTA) of last stage effluents samples generated during Ogi, and Cassava fufu production revealed that the pH of the samples ranges from 3.1 to 5.3 and the TTA ranges from 0.21 to 0.26 %. The pH and TTA of the samples clearly showed that they were acidic. It revealed that the maximum optical density values at 0.2% and 0.3% bile tolerance were 2.40±0.75 and 3.62±0.11 for LAB 9. All the isolates showed appropriate growth in the presence of bile and acid tolerance pH3-pH7. The safety evaluation of the LAB strains revealed negative hemolysis (Gamma hemolysis) and negative DNase activity. Results of antibacterial activity indicate that the LAB strains from Ogi and Cassava last stage effluent samples were found to inhibit the growth of most of the pathogenic clinical strains of S. aureus, E. coli, K. pneumoniae, and B. subtilis with the highest inhibition zones exhibited from the LAB strains was 23 mm. LAB1, LAB 2, LAB 3, LAB5, LAB6, LAB9, and LAB10 showed no inhibition activity against E. coli. Our overall findings indicate that 10 LAB strains displayed varying species-specific inhibition and their varying in vitro bioassay should not undermine the potential probiotics' desirable characteristics but rather substantiate their role in vivo evaluation of the strain for their potential as desirable probiotics that could be harnessed and used for the formulation of nutriceutical supplement to improve human wellbeing.

The present study aimed at characterizing lactic acid bacteria (LAB) strains isolated from traditional sourdoughs collected in different regions of Morocco. Isolated strains were firstly identified using Gram staining and catalase reaction test. Presumptive LAB strains were then checked for various phenotypical properties including growth at 45°C, resistance to NaCl, enzyme production, acidification capacity, diacetyl and exopolysaccharide (EPS) production, and antifungal activity. Finally, selected LAB strains were identified using 16S rDNA sequencing. Results showed that 32.1% of the isolates were thermophilic (45°C) and 83.9% were resistant to NaCl (6.5%). Moreover, 51.7 and 37.5% were able to produce diacetyl and EPS, respectively. Regarding enzyme production, 55.3 and 7.1% of the isolates showed lipolytic and proteolytic activities, respectively. Low pH values (3.37-3.76) were obtained after 24h of incubation of LAB strains in de Man, Rogosa and Sharpe (MRS) broth. Antifungal activity test against Aspergillus flavus, Aspergillus niger and Penicillium spp. showed an inhibition rate up to 50%. Bacterial DNA sequencing showed that LAB isolates belong to seven species, chiefly Levilactobacillus brevis, Lentilactobacillus parabuchneri, Lactiplantibacillus plantarum, Pediococcus pentosaceus, Enterococcus hirae, Bifidobacterium pseudocatenulatum, and Companilactobacillus paralimentarius. These findings, for the first time in Moroccan sourdoughs, indicate that the isolated LAB strains have good multifunctional properties and could be suitable as good starters for sourdough bread production under controlled conditions.

Fermented vegetable products play a significant role in various cuisines, and understanding the fermentation dynamics of lactic acid bacteria (LAB) strains is essential for optimizing their production and quality. Here, we sought to investigate the fermentation performance of five LAB strains isolated from Sichuan paocai as starters for paocai. Sensory evaluation revealed that the inoculation of radish paocai samples with LAB strains effectively improved the overall liking and sensory satisfaction of participants, increasing the scores to varying degrees in terms of taste, flavor, texture, and coloration. Lactiplantibacillus plantarum and Lacticaseibacillus rhamnosus exhibited a good salt resistance in radish juice and could grow in a medium containing 10% NaCl. Four indicator strains commonly found in contaminated paocai were effectively inhibited by fermented LAB broths, which improved the edibility and safe production of paocai. Compared to spontaneous fermentation (CK), radish paocai inoculated with LAB showed a significantly accelerated acid production rate, shortening the fermentation period by approximately two days. The contents of titratable total acids, organic acids, and free amino acids were higher in the inoculated samples and were enriched in the taste of radish paocai. The content of volatile organic compounds in the inoculated samples was higher than that in CK. Based on OPLS-DA analysis, 31 key indicators of paocai quality were screened and used to rank the fermentation performances of the five strains using the TOPSIS method; here, Lpb. plantarum and Lcb. rhamnosus achieved the highest scores. This study provides a reference for selecting LAB strains as efficient and secure fermentation starters to optimize paocai quality.

This study investigated the probiotic potentials of seven lactic acid bacteria (LAB) strains at different temperatures, pH, and bile salt concentrations. Their antimicrobial activity and antibiotic susceptibility were also determined. There were significant (P˂0.05) differences in the LAB growth at 45-650C with viable counts ranging from 4.28-8.34 Log10 Cfu/ml after 48 h. The LAB strains showed significant (P˂0.05) increase at pH 2, 2.5 and 3 after 3 and 6 h. L. parabuchneri LMG was viable at 45 and 65oC with 99.30 and 65.00% survival respectively. The LAB showed high resistance to 0.3% bile salt at 97.90%. L. plantarum CIP was viable with 95.40% survival at pH 3.0 after 3 h. All the LAB strains were susceptible to cefuroxime (20 µg/ml) and erythromycin (10 µg/ml) at 13.00-45.00 mm zone of inhibition (ZOI). They had strong antimicrobial activity against Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 9027 and Listeria monocytogenes ATCC 15313. Leuconostoc mesenteroides LM and L. brevis ATCC inhibited the five tested food borne pathogens with ZOI varying from 8.00-26.00 mm. The results from this study showed that the LAB strains isolated from fermented foods had probiotic potential and can be used for research and commercial purposes.

Exploring the impact of lactic acid bacteria on the biocontrol of toxigenic Fusarium spp. and their main mycotoxins

Twenty two strains of lactic acid bacteria (LAB) were isolated from 30 samples of commercial Nigerian bottled yoghurt (produced on a small scale). Isolates were phenotypically characterized and their technological properties such as acidification, exopolysaccharides (EPS) production, enzymatic activities, biogenic amine production and bacteriocin production were studied following standard procedures. The population of LAB in the yoghurt samples varied between 0.00 and 6.63 log cfu ml-1. The pH and titratable acidity ranged from 3.80 to 4.48 and 0.73 to 1.78% lactic acid respectively. The isolated LAB strains belonged to Lactobacillus, Lactococcus, Leuconostoc, Streptococcus and Enterococcus genera. Thirteen strains showed proteolytic activity while four strains showed high lipolytic activity. The LAB strains exhibited medium to low acidification activities. About 77% of the LAB strains produced EPS. Six strains produced biogenic amines. Seven strains showed antagonistic properties due to organic acid against indicator organisms (Staphylococcus aureus, Klebsiella pneumoniae, Escherichia coli and Proteus vulgaris) while two strains (Enterococcus faecalis and Lactococcus cremoris) produced additional inhibitory substances againstK. pneumoniae. The results revealed that the assayed commercial Nigerian bottled yoghurts contain several LAB species and genera different from Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus. The production of biogenic amine by some of the LAB strains is undesirable in yoghurt. The technological properties of the LAB associated with the fermented milk produced on a small scale will help in the selection and development of beneficial strains as starter or adjunct cultures. Key words: Yoghurt, lactic acid bacteria, technological properties, strain selection.

Eighteen lactic acid bacteria (LAB) strains, isolated from coffee pulp silages were characterized according to both growth and gallic acid (GA) consumption. Prussian blue method was adapted to 96-well microplates to quantify GA in LAB microcultures. Normalized data of growth and GA consumption were used to characterize strains into four phenotypes. A number of 5 LAB strains showed more than 60% of tolerance to GA at 2 g/l; whereas at 10 g/l GA growth inhibition was detected to a different extent depending on each strain, although GA consumption was observed in seven studied strains (>60%). Lactobacillus plantarum L-08 was selected for further studies based on its capacity to degrade GA at 10 g/l (97%). MRS broth and GA concentrations were varied to study the effect on growth of LAB. Cell density and growth rate were optimized by response surface methodology and kinetic analysis. Maximum growth was attained after 7.5 h of cultivation, with a dilution factor of 1-1/2 and a GA concentration between 0.625 and 2.5 g/l. Results indicated that the main factor affecting LAB growth was GA concentration. The main contribution of this study was to propose a novel adaptation of a methodology to characterize and select LAB strains with detoxifying potential of simple phenolics based on GA consumption and tolerance. In addition, the methodology presented in this study integrated the well-known RSM with an experimental design based on successive dilutions.

Autochthonous microbiota from artisanal cheeses is predominantly composed of lactic acid bacteria (LAB), which are able to produce antimicrobial compounds, such as bacteriocins, suggesting their application in food biopreservation. Knowledge about LAB growth and bacteriocin production during food production and conservation is essential to determine their use. In this way, the study aimed at isolating bacteriocinogenic LAB from twenty-one artisanal cheeses from the western region of Parana state, Brazil, determining the best conditions for growth and bacteriocin production (25°C, 30°C, and 37°C/24h); bacteriocin stability under different ranges of pH (2, 4, 6, 8, and 10 for 2h) and temperature (60oC/2h; 80oC/2h; 121oC/15min). Their activity against different target microorganisms was also evaluated. A total of 34 LAB strains presented characteristics compatible with bacteriocin production. Most of them presented better results for bacteriocin production when cultured at 25ºC and 30ºC. Bacteriocins remained active against L. monocytogenes when exposed from pH 4 to 8 and a wide temperature range; some bacteriocins were even resistant to sterilization temperatures. Bacteriocins produced were able to inhibit spoilage and pathogenic microorganisms, such as L. monocytogenes, B. cereus, and P. fluorescens. These results indicated that isolated bacteriocinogenic LAB present potential to be used as food biopreservatives.

In this study, lactic acid bacteria (LAB) strains were isolated from fermented grains of traditional Chinese Baijiu, and their probiotic properties were characterized. Eleven out of 29 LAB strains showed good tolerance to the gastrointestinal tract and bile salts. The surface characteristics (auto-aggregation, co-aggregation, hydrophobicity), safety (hemolytic and antibiotic sensitivity), antibacterial activity against three foodborne pathogens, and antioxidant and hypoglycemic properties of the 11 LAB strains were investigated. Principal component analysis (PCA) was used to comprehensively evaluate LAB strains and their probiotic properties. It was found that Weissella cibaria (OP288150), Pediococcus acidilactici (OP288151), Pediococcus pentosaceus (OP288154), Pediococcus pentosaceus (OP288156) and Levilactobacillus brevis (OP288158) showed high probiotic properties, with potential for commercial development. The results also demonstrated that fermented grains of Chinese Baijiu can be used as a source of high-quality probiotics.

Probiotics incorporated into edible film coatings (EFCs) represent an innovative technology to enhance probiotic delivery and stability in functional foods. The present study aims to develop and evaluate the effectiveness of an EFC in protecting the viability of three probiotic lactic acid bacteria (LAB) strains under acidic conditions, within food matrices, and during storage. Edible film coating consisted of hydrocolloidal biomolecule whey protein concentrate, sodium alginate, and glycerol (2:0.5: 0.5% wt/vol). Three well-characterised probiotic LAB strains, Lacticaseibacillus paracasei K-04, Lactiplantibacillus plantarum M-02, and Lacticaseibacillus rhamnosus SM, were isolated from traditional Egyptian fermented foods and encapsulated using standardised EFC protocol. The biscuits and dry dates were fortified with a multistrain probiotic mixture encapsulated in EFC probiotic LABs. The morphology of the probiotics LAB strains was characterised by scanning electron microscopy. The safety assessment of the three LAB strains was conducted based on their antibiotic susceptibility and haemolytic activity. Survival was assessed under acidic pH and simulated gastric digestion. Antibacterial activity against pathogenic bacteria, antioxidant capacity, and probiotic viability during storage of functional probiotic biscuits (FPBs) were also evaluated. None of the studied LAB strains exhibited haemolytic activity, indicating an absence of virulence-associated traits. Furthermore, all strains demonstrated susceptibility to most of the tested antibiotics, with resistance limited to a few agents. The total viable LAB count averaged 5.39 × 107 CFU/g in biscuit and 1.60 × 107 CFU/g in dry dates. The EFC LAB strains exhibited significantly higher survival rates (p < .05) than the respective free cells. The same trend was obtained with simulated gastric digestion. Interestingly, EFC forms showed enhanced antibacterial activity compared to the respective free against all tested pathogenic bacteria (p < .05). Similarly, the antioxidant activity of EFC was significantly higher (p < .05) compared to the respective free forms. The FPBs and functional probiotic date (FPDs) had no adverse effect on the sensory characteristics. After 4 weeks of storage at 4 °C, FPBs maintained viable LAB counts above 1.08 × 106 CFU/g of biscuit, exceeding the minimum recommended threshold. The ingredients used for the development of the functional biscuits and dates are locally sourced, tasteless, cost-effective, and environmentally sustainable. The introduction of these probiotic-enriched products into the Egyptian food systems offers, as they align with traditional dietary habits and require no significant changes in consumer behaviour. This approach represents an accessible and practical strategy to promote public health and contribute to disease prevention at the population level.

Vinegar is a special fermented product in our daily lives. In this study, vinegar-derived acetic acid bacteria (AAB) and lactic acid bacteria (LAB) strains were evaluated in terms of multifunctional properties such as viability in harsh conditions, safety, technological properties, antimicrobial activity, in vitro adhesion. All AAB strains grew at pH 2, 3, and 4, while all LAB strains except for five Lacticaseibacillus paracasei strain (IGFVL5, IGFVL4, IGMVL5, and IGMVL6) and Lactiplantibacillus plantarum IGFVL12 grew only at pH 3 and 4. However, all these strains exhibited high viability in the presence of bile salts, pepsin, pancreatin, and phenol at various levels (18.63%-200.09%). Besides, most AAB strains resisted ampicillin, chloramphenicol, and erythromycin, whereas LAB strains were susceptible. Although all AAB strains grew at 1.5% and 10% NaCl, nine LAB strains grew at these conditions. Only La. paracasei IGFVL19 and Lac. plantarum IGFVL17 had β-galactosidase activity, while the proteolytic activity of twelve strains ranged from 0.003 to 0.043mg tyrosine/mL. Eight AAB and eleven LAB strains had antibacterial activity, with inhibition zones ranging from 6.33 to 18.00mm against all test bacteria (Salmonella Typhimurium NRRL B-4420, E. coli O157:H7 ATCC 43895, Escherichia coli DSM 1103, Bacillus subtilis ATCC 6037, Listeria monocytogenes Scott A, Enterococcus faecalis ATCC 29212, and Staphylococcus aureus ATCC 6538P). Moreover, AAB and LAB strains, except for Acetobacter pasteurianus (IGFVA7), A. ghanensis (IGFVA8 and IGFVA10), A. fabarum IGFVA13, La. paracasei (IGFVL4, IGAVL1, and IGVAL2) showed auto-aggregation ability ranging from 0.82% to 54.47% and these percentages increased depending on the incubation time. Lastly, according to the cumulative probiotic scores from all the results La. paracasei IGFVL19, La. paracasei IGFVL21, and Lev. brevis IGFVL18 have potential to be used as innovative probiotics for applications in the food industry with further in vivo tests.

Eight lactic acid bacteria (LAB) strains isolated from five naturally‐fermented silages of different ensilage materials on the Tibetan Plateau were characterized and their effects on the silage quality of oat (Avena sativa L.) straw were studied. These LAB isolates were evaluated using morphological, physiological and biochemical tests. All eight strains (M1, LM8, LO7, LOG9, LCG3, LTG7, I5 and LI3) could grow at 5–20°C, pH 3.5–7.0 and NaCl (3.0, 6.5%) and they were identified as Lactobacillus plantarum, L. coryniformis, Pediococcus pentosaceus, P. acidilactici, L. plantarum, P. acidilactici, L. paraplantarum and L. casei by sequencing 16S rDNA, respectively. The eight isolated strains and one commercial inoculant (L. plantarum MTD‐1) were subsequently added to oat straw for ensiling 35 days. All the LAB strains improved the silage quality of oat straw, evidenced by significantly (P < 0.05) higher lactic acid (LA) and residual water soluble carbohydrate (WSC) contents and ratios of LA to acetic acid (LA/AA), and significantly (P < 0.05) lower pH and ammonia nitrogen contents. ‘LOG9’ performed best among all LAB strains, evidenced by the highest (P < 0.05) LA (94.19 g kg−1 dry matter [DM]) and residual WSC contents (44.53 g kg−1 DM) and ratio of LA/AA (18.18) and LAB count (8.86 lg cfu g−1 fresh weight), and the lowest (P < 0.05) pH (3.87), this might be related to its host specificity. Strain LOG9 is recommended as starter culture for oat straw silage.