Screening of lactic acid bacteria for antimicrobial properties from mayonnaise-based products and raw materials

Characterization of Lactic Bacteria Isolated from Raw Milk and Their Antibacterial Activity against Bacteria as the Cause of Clinical Bovine Mastitis

The objectives of this study were the selection of lactic acid bacteria (LAB) isolated from raw milk and studying their technological properties and antibacterial activities against bacteria as the cause of cattle mastitis. Biochemical and molecular identification using 16S–23S rRNA gene spacer analysis and 16S rRNA gene sequencing highlighted the presence of three species: Lactiplantibacillus plantarum, Lactococcus lactis, and Levilactobacillus brevis. The enzymatic characterization followed by the determination of technofunctional properties showed that LAB strains did not exhibit any hemolytic effect and were able to produce protease and lipase enzymes. Isolates showed very high antagonistic activity against Gram-positive and Gram-negative bacteria by producing H2O2, bacteriocin(s), and organic acid(s). APIZYM micromethod demonstrated that all selected strains are capable of producing valine arylamidase, cystine arylamidase, N-acetyl-β-glucosaminidase, and ᾳ-mannosidase. The antibiotic susceptibility assay showed that all selected strains were sensible to the majority of tested antibiotics. Based on these results, it can be concluded that the technological properties of the selected LAB allow considering their industrial use in order to formulate bioactive functional foods or drug(s).

Design and Application of Hydrocolloids from Butternut Squash (Cucurbita moschata) Epidermis as a Food Additive in Mayonnaise-type Sauces

Hydrocolloids play a fundamental role in the design of new food products in their structure and functionality due to the interaction with the components of complex food matrices; for this reason, natural sources that are friendly to the environment must be sought for their extraction. A microstructure product such as mayonnaise is an oil-in-water-type emulsion design with the components of the complex varying from egg yolk, additives, spices, sugar, and other optional ingredients to improve its stabilities and organoleptic characteristics. The main objective of the study was to design and characterize the physicochemical, bromatological, and sensory analyses and rheological properties of the mayonnaise-type sauce formulated with hydrocolloids obtained from the epidermis of butternut squash (Cucurbita moschata) and xanthan gum. The rheological study allowed us to obtain a behavior of a non-Newtonian flow of the shear-thinning type for all the samples, and flow curves could be well described by the Carreau model (R ² ≥ 0.993). The samples exhibit a more elastic than viscous behavior, with a higher storage modulus than the loss modulus (G' > G″) in the evaluated frequency range. When performing the physicochemical analysis, pH values (4.02-4.28), titratable acidity (0.40-0.48), peroxide index (12.5-20 meq), and a stable behavior were achieved in all the formulations except for MS2, which showed instability. Regarding the sensory evaluation, the MS3 sample reflected the closest values to the control sample, with a higher level of satisfaction. On the other hand, the bromatological analysis of MS3 presented a humidity value of 55.3 ± 0.27; carbohydrates, 7.66 ± 0.42; protein, 0.87 ± 0.02; fiber, 0.94 ± 0.05; and ash, 0.54 ± 0.05. The development of this product contributes to the transformation and agro-industrial use of the butternut squash (C. moschata); likewise, it allows us to obtain a mayonnaise-type sauce with organoleptic and nutritional characteristics for human consumption.

Characterization of Lactobacillus species proposed as probiotics

An isolated Lactobacillus from several various sources were identified depending on morphological, microscopically and biochemical tests in vitro analysis of probiotic properties that included: an ability to tolerate in different concentration of bile salt, survival in acidic conditions, their antimicrobial activity, and S-layer characterizations were carried out. It was noticed that isolates of Lactobacillus rhamnosus and L. delbrueckii have a broad activity of antimicrobial and found the isolate L. rhamnosus represented with a survival percentage 6.9% at pH 4.5 and 5.1% at pH 2.0) also L. rhamnosus (5.7% at pH 4.5 and 4.9% at pH 2.0) tolerated acidic media, Lactobacillus spp. has antimicrobial activity against all gram-positive and negative tested isolates. 70 kDa of S-layer protein bands were detected with whole-cell SDS-PAGE analysis, and it's predominant in cells of isolates which grown in MRS broth anaerobically. It was noticed that the collected Lactobacillus isolates could be used as probiotic.

Screening of indigenous oxalate degrading lactic acid bacteria from human faeces and South Indian fermented foods: assessment of probiotic potential

Lactic acid bacteria (LAB) have the potential to degrade intestinal oxalate and this is increasingly being studied as a promising probiotic solution to manage kidney stone disease. In this study, oxalate degrading LAB were isolated from human faeces and south Indian fermented foods, subsequently assessed for potential probiotic property in vitro and in vivo. Based on preliminary characteristics, 251 out of 673 bacterial isolates were identified as LAB. A total of 17 strains were found to degrade oxalate significantly between 40.38% and 62.90% and were subjected to acid and bile tolerance test. Among them, nine strains exhibited considerable tolerance up to pH 3.0 and at 0.3% bile. These were identified as Lactobacillus fermentum and Lactobacillus salivarius using 16S rDNA sequencing. Three strains, Lactobacillus fermentum TY5, Lactobacillus fermentum AB1, and Lactobacillus salivarius AB11, exhibited good adhesion to HT-29 cells and strong antimicrobial activity. They also conferred resistance to kanamycin, rifampicin, and ampicillin, but were sensitive to chloramphenicol and erythromycin. The faecal recovery rate of these strains was observed as 15.16% (TY5), 6.71% (AB1), and 9.3% (AB11) which indicates the colonization ability. In conclusion, three efficient oxalate degrading LAB were identified and their safety assessments suggest that they may serve as good probiotic candidates for preventing hyperoxaluria.

Novel probiotic candidates for humans isolated from raw fruits and vegetables

This study was aimed at determining the probiotic potential of a large number of autochthonous lactic acid bacteria isolated from fruit and vegetables. Survival under simulated gastric and intestinal conditions showed that 35% of the strains, mainly belonging to the species Lactobacillus plantarum maintained high cell densities. Selected strains did not affect the immune-mediation by Caco-2 cells. All strains stimulated all 27 immune-mediators by peripheral blood mononuclear cells (PBMC). A significant (P<0.05; P<0.01) increase of the major part of cytokines and growth factors was found. A few chemokines were stimulated. Immune-mediators with pro-inflammatory activity (IL-17, EOTAXIN and IFNγ) were significantly (P<0.01) stimulated by all strains, followed by IL-1b>IP-10>IL-6>MIP1α. Stimulation of IL-12, IL-2 and IL-7 was strain dependent. Only a few strains increased the synthesis of cytokines with anti-inflammatory activity. Six L. plantarum strains were further selected. Four were defined as the strongly adhesive strains (more than 40 bacteria adhering to one Caco-2 cell), and 2 as the adhesive strains (5-40 bacteria adhering to one Caco-2 cell). Five strains grew and acidified chemically defined medium with fructo-oligosaccharides (FOS) as the only carbon source. End-products of FOS fermentation were found. All strains inhibited enterohemorragic Escherichia coli K12 and Bacillus megaterium F6 isolated from human sources. The results of this study showed that some autochthonous lactic acid bacteria from raw fruit and vegetables have functional features to be considered as novel probiotic candidates.

Probiotic attributes ofLactobacillusstrains isolated from food and of human origin

Lactobacilli isolated from various sources were identified on the basis of 16S–23S rRNA gene intergenic region amplification and subsequent sequencing of the smaller intergenic region. Anin vitroanalysis of probiotic properties including binding, ability to tolerate different concentrations of bile, survival in acidic buffer and antimicrobial activity of four different isolates and two standard strains (Lactobacillus plantarumAmerican Type Culture Collection (ATCC) 8014 andL. rhamnosusGG (LGG)) was carried out. The ability of each isolate to stimulate Caco-2 cells, human peripheral blood mononuclear cells (PBMC) and THP-1 cells resulting in immunomodulation of these cells was analysed. IsolatesL. rhamnosusCS25 andL. delbrueckiiM and standard strain ATCC 8014 showed broad antimicrobial activity, and isolates CS25 (percentage of survival 6·9 % at pH 2·5, 5·1 % at pH 2·0) andL. plantarumCS23 (5·7 % at pH 2·5, 4·9 % at pH 2·0) have shown good tolerance to acidic pH. Isolate CS23 showed a good survival (14 %) after 2 h incubation in de Man, Rogosa and Sharpe (MRS) medium containing 3 % bile salts. Isolates CS23, CS25 andL. fermentumASt1 could stimulate Caco-2 cells, human PBMC and THP-1 cells for a strong and varied immunomodulatory response in these cells. Though LGG showed poor antimicrobial activity as well as bile and acid tolerance, it was found to be the best binding strain tested. Child faecal isolate CS23 from the present study showed high binding ability (seventeen bacteria/Caco-2), high tolerance to acidic pH and bile salts and significant immunomodulation; therefore it is a good potential probiotic candidate.