Characterization of Riboflavin-Producing Strains of Lactobacillus plantarum as Potential Probiotic Candidate through in vitro Assessment and Principal Component Analysis

Ameliorative potential of synbiotic combination of Lactobacillus sp. and polyphenols against Benzo[a]pyrene-induced toxicity in Caco-2 cell line

Exposure to benzo[a]pyrene (B[a]P), a major global food safety concern, is often associated with increasing incidence of colorectal cancers. This in-vitro study was focused on the identification of potential B[a]P-adsorbing Lactobacillus strains and evaluation of the ameliorative effect of synbiotic combination of selected Lactobacillus sp. and polyphenols (quercetin or resveratrol) against B[a]P-induced intestinal toxicity in Caco-2 cells. Preliminary studies lead to the selection of Lactiplantibacillus plantarum MTCC 25433 strain that showed 86% of B[a]P adsorption in 2 h as compared to L. rhamnosus GG that showed 74% of B[a]P adsorption. B[a]P adsorption by MTCC 25433 was reduced to 9%, 16% and 20% upon pre-treatment with SDS, NaIO4 and mutanolysin, attributing the involvement of cell wall proteins and polysaccharides in the adsorption. Additionally, peptidoglycan of both strains adsorbed >50% of B[a]P. In-vitro assays revealed that the selected LAB mitigated the B[a]P-induced epithelial cell damage. Among the polyphenols, quercetin, resveratrol and curcumin, varied in their potency to mitigate B[a]P-induced oxidative stress, with curcumin being least effective. Combinations of selected Lactobacillus sp. and polyphenols were more potent in averting B[a]P-induced toxicity via increase in GSH (17-30 %), SOD (50-88 %), catalase (19-45 %), and reduction in IL-8 secretion (14-28 %) and barrier dysfunction. Principal component analysis affirmed the superior potency of combination of L. plantarum MTCC 25433 and quercetin in averting B[a]P-induced toxicity. Overall, this study highlighted a novel promising strategy of synbiotic combination of Lactobacillus sp. and polyphenols (quercetin or resveratrol) in alleviating the B[a]P-induced toxicity in intestinal epithelial cells.

Prevalence of antibiotic resistance in lactic acid bacteria isolated from traditional fermented Indian food products

The emergence of antimicrobial resistance (AMR) in lactic acid bacteria (LAB) raises questions on qualified presumptive safety status and poses challenge of AMR transmission in food milieu. This study focuses on isolation, identification and characterization of AMR in LAB prevalent in traditional fermented Indian food products. The analysis of 16SrRNA based phylogenetic tree showed placements of isolates among four different genera Lactobacillus, Enterococcus, Weissella and Leuconostoc. In E-strip gradient test of susceptibility to 14 different antibiotics, over 50% of isolates showed resistance to ampicillin, chloramphenicol, ciprofloxacin, erythromycin, kanamycin, linezolid, streptomycin, trimethoprim and vancomycin. A multivariate principal component analysis, an antibiogram and multiple antibiotic resistance index-values (> 0.2) indicated presence of multidrug-resistance among the isolates. This study reports prevalence of an alarmingly high rate of AMR LAB strains in traditional fermented foods and is important to regulators and public health authorities for developing strategies to control transmission in food systems.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01305-1.

Complete genome sequence of Lactiplantibacillus plantarum BBC32B isolated from human feces sample

We report complete genome sequence of Lactiplantibacillus plantarum BBC32B, which was isolated from human feces sample and submitted to Microbial-Type Culture Collection (MTCC), India with deposition number MTCC 25432. The bacteria from Lactobacillaceae family contained 3,411,152 bp; 3,425 protein coding genes, sharing 69.67% average nucleotide identity with closest species of Lactobacillus brevis ATCC367.

Biofilm formation in food processing plants and novel control strategies to combat resistant biofilms: the case of Salmonella spp

Salmonella is one of the pathogens that cause many foodborne outbreaks throughout the world, representing an important global public health problem. Salmonella strains with biofilm-forming abilities have been frequently isolated from different food processing plants, especially in poultry industry. Biofilm formation of Salmonella on various surfaces can increase their viability, contributing to their persistence in food processing environments and cross-contamination of food products. In recent years, increasing concerns arise about the antimicrobial resistant and disinfectant tolerant Salmonella, while adaptation of Salmonella in biofilms to disinfectants exacerbate this problem. Facing difficulties to inhibit or remove Salmonella biofilms in food industry, eco-friendly and effective strategies based on chemical, biotechnological and physical methods are in urgent need. This review discusses biofilm formation of Salmonella in food industries, with emphasis on the current available knowledge related to antimicrobial resistance, together with an overview of promising antibiofilm strategies for controlling Salmonella in food production environments.

Exploration of probiotic attributes in lactic acid bacteria isolated from fermented Theobroma cacao L. fruit using in vitro techniques

Probiotics are known for their health-promoting properties and are recognized as beneficial microorganisms. The current investigation delves into the isolation and comprehensive in vitro characterization of lactic acid bacteria (LAB) obtained from the Indian-origin Theobroma cacao L. Forastero variety to assess their potential as probiotic candidates. Eleven LAB isolates were obtained, and among them, five exhibited classical LAB traits. These five isolates underwent rigorous in vitro characterization to evaluate their suitability as probiotics. The assessments included resilience against acid and bile salts, which are crucial for probiotic viability. Additionally, the isolates were subjected to simulated gastric and pancreatic fluids and lysozyme exposure to assess their survival rates. Auto- aggregation, co-aggregation, hydrophobicity, and exopolysaccharide production were also examined. The inhibitory potential of α-glucosidase, an enzyme related to glucose metabolism, was measured, and antioxidant activity was evaluated using DPPH and ABTS assays. A safety assessment was conducted to confirm the non-pathogenic nature of the isolates. Among the five isolates, CR2 emerged as a standout candidate with maximal bile salt hydrolase activity, phenol resistance, and lysozyme resistance. CR2 and CYF3 exhibited notable survival rates under simulated conditions. The isolates displayed variable degrees of auto-aggregation, co-aggregation, and hydrophobicity. CR2 exhibited the highest exopolysaccharide production (0.66 mg/mL), suggesting diverse applications in the food industry. CR2 also demonstrated the highest inhibition rate against α-glucosidase (56.55%) and substantial antioxidant activity (79.62% DPPH, 83.45% ABTS). Safety assessment confirmed the non- pathogenic nature of the isolates. Molecular characterization identified CR2 as Lactococcus lactis subsp. lactis and CYF3 as Limnosilactobacillus fermentum. Both strains exhibited commendable probiotic and technological attributes, positioning them as promising candidates for functional foods and beyond. This study provides valuable insights into the in vitro characterization of LAB isolated from Indian Theobroma cacao L., highlighting their potential as probiotic candidates with advantageous traits, including survival in hostile conditions, beneficial enzymatic activities, bioactivity, and other essential attributes.

Microencapsulation of riboflavin-producing Lactiplantibacillus Plantarum MTCC 25,432 and Evaluation of its Survival in Simulated Gastric and Intestinal Fluid

Microencapsulation is an optimistic method for the delivery of live microbial cells through different food products. In this study, riboflavin-producing probiotic strain Lactiplantibacillus plantarum MTCC 25,432 was encapsulated using a spray drying technique with different wall materials including Inulin, maltodextrin (MD), and MD + Inulin (1:1). The obtained spray dried powder was investigated for probiotic viability, encapsulation efficiency, particle size, water activity, moisture content, hygroscopicity, bulk and tapped densities, storage stabilities, Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Besides this, the viability of the free and encapsulated probiotic cells was tested under simulated gastric and intestinal fluid conditions. In the results, microcapsules produced with the combination of MD + Inulin showed higher dry powder yield (36.5%) and viability of L. plantarum MTCC 25,432 (7.4 log CFU / g) as compared with individual coating materials. Further characterization revealed that MD + Inulin microcapsules are spherical (3.50 ± 1.61 μm in diameter) in shape with concavities, showed the highest encapsulation efficiency (82%), low water activity (0.307), moisture content (3.67%) and good survival ability at low pH (pH 2.0 and 3.0), high bile salt concentrations (1.0% and 2.0%), and long storage conditions. No differences in FTIR spectra were observed among the tested samples. However, TGA showed enhanced thermal stability of probiotic-loaded microcapsules when MD + Inulin was used together. In conclusion, MD + Inulin could be a potential encapsulation material for riboflavin-producing probiotic bacteria L. plantarum MTCC 25,432.

Functional Characterization of Lactobacillus plantarum Isolated from Cow Milk and the Development of Fermented Coconut and Carrot Juice Mixed Beverage

Screening probiotics are crucial for assessing their safety, security, and further production of functional foods for human health. The present study aimed to isolate and identify bacteria from raw cow's milk samples that exhibit health benefits upon consumption. We characterized the probiotic properties of Lactobacillus plantarum (also called Lactiplantibacillus plantarum) strains CMGC2 and CMJC7 isolated from cow milk by in vitro study. The strains exhibited tolerance to simulated gastric conditions and were further identified by 16S rRNA sequencing as Lactobacillus plantarum (L. plantarum) CMGC2 and CMJC7. Both isolates were evaluated in vitro for their probiotic attributes, viz. hydrophobicity, autoaggregation, co-aggregation, lysozyme tolerance, antibacterial activity, antibiotic susceptibility, hemolytic activity, and phenol tolerance. The isolates CMGC2 and CMJC7 showed excellent probiotic attributes; hence, both strains were selected to produce coconut and carrot juice mixed beverages (CCMB). The CCMB was evaluated for the pH, acid-production rate, and total viable bacterial counts. The results showed that the CCMB was an excellent medium for the growth of CMGC2 and CMJC7 as it supported adequate growth of organisms (8.93 CFU/mL and 8.68 CFU/mL, respectively) even after 48 h of incubation. In conclusion, CMGC2 and CMJC7 can be used to develop different beverages possessing nutritive and probiotic values, and these beverages can be used for producing unique products.

Probiotic assessment and antioxidant characterization of Lactobacillus plantarum GXL94 isolated from fermented chili

Oxidative stress is caused by an imbalance between prooxidants and antioxidants, which is the cause of various chronic human diseases. Lactic acid bacteria (LAB) have been considered as an effective antioxidant to alleviate oxidative stress in the host. To obtain bacterium resources with good antioxidant properties, in the present study, 113 LAB strains were isolated from 24 spontaneously fermented chili samples and screened by tolerance to hydrogen peroxide (H2O2). Among them, Lactobacillus plantarum GXL94 showed the best antioxidant characteristics and the in vitro antioxidant activities of this strain was evaluated extensively. The results showed that L. plantarum GXL94 can tolerate hydrogen peroxide up to 22 mM, and it could normally grow in MRS with 5 mM H2O2. Its fermentate (fermented supernatant, intact cell and cell-free extract) also had strong reducing capacities and various free radical scavenging capacities. Meanwhile, eight antioxidant-related genes were found to up-regulate with varying degrees under H2O2 challenge. Furthermore, we evaluated the probiotic properties by using in vitro assessment. It was showed that GXL94 could maintain a high survival rate at pH 2.5% or 2% bile salt or 8.0% NaCl, live through simulated gastrointestinal tract (GIT) to colonizing the GIT of host, and also show higher abilities of auto-aggregation and hydrophobicity. Additionally, the usual antibiotic susceptible profile and non-hemolytic activity indicated the safety of the strain. In conclusion, this study demonstrated that L. plantarum GXL94 could be a potential probiotic candidate for producing functional foods with antioxidant properties.

In Vitro Assessment of Probiotic and Technological Properties of Lactic Acid Bacteria Isolated from Indigenously Fermented Cereal-Based Food Products

The present study concerns the isolation and characterization of potential probiotic bacteria isolated from indigenously fermented cereal-based products commonly produced by tribal people of the Aravali hills region of India and the documentation of their unexplored probiotic attributes. The isolated strains were evaluated for probiotic attributes, such as bile salt and acid tolerance, lysozyme and phenol tolerance, antagonistic and antifungal activity, cell autoaggregation, cell-surface hydrophobicity, simulated gastric and pancreatic digestion, antioxidative potential, bile salt hydrolase activity, and H2O2 production. The safety of isolates was assessed by antibiotic sensitivity, hemolytic activity, DNase activity, and biogenic amine production assays, while technological properties, such as fermenting ability, amylolytic activity, and EPS production, were also evaluated. A total of 70 LAB isolates were screened initially, and 6 strains showed good potential as probiotic candidates in in vitro assessments. The efficient strains were identified using phenotyping and biochemical characterization, which results were further confirmed and recognized at the strain level using phylogenetic analysis and 16S rDNA sequencing. The current study has shown that Lactiplantibacillus plantarum KMUDR7 isolated from “Makka ki Raab” has excellent probiotic attributes and could be a potential probiotic for product preparation. However, other strains, Lactobacillus delbrueckii subsp. bulgaricus KMUDR1 and Lacticaseibacillus rhamnosus KMUDR9, showed good properties, while KMUDR14, -17, and -20 also have comparable probiotic attributes.

A statistical optimization by response surface methodology for the enhanced production of riboflavin from Lactobacillus plantarum–HDS27: A strain isolated from bovine milk

In the present study, Lactobacillus plantarum-HDS27 strain isolated from bovine milk was used for the enhanced production of riboflavin. Production medium was optimized by one factor at a time with different parameters. Statistical optimization by Response surface methodology (RSM), central composite design was used to optimize variables such as pH, temperature, glucose, and yeast extract. The present study reveals the maximum riboflavin production by one factor at a time was obtained under the culture conditions; glucose, yeast extract, pH 6, the temperature at 40°C, and 3% of inoculum size. In RSM, analysis of variance for the responses was calculated. Among the tested variables, pH, yeast extract, and temperature showed significant impact on riboflavin production. Maximum amount of yeast extract in production medium resulted in increased riboflavin production. The riboflavin production after 24 h with the optimal condition was found to be 12.33 mg/L. It was found proximate to the expected value (12.29 mg/L) achieved by the RSM model. The yield of riboflavin was increased to 3.66-fold after 24 h with the optimized parameters. The current research, emphasizes that the Lactobacillus plantarum–HDS27 could be an excellent strain for the large-scale industrial production of riboflavin.

Strategies for the Identification and Assessment of Bacterial Strains with Specific Probiotic Traits

Early in the 1900s, it was proposed that health could be improved and senility delayed by manipulating gut microbiota with the host-friendly bacteria found in yogurt. Later, in 1990, the medical community reconsidered this idea and today probiotics represent a developed area of research with a billion-dollar global industry. As a result, in recent decades, increased attention has been paid to the isolation and characterization of novel probiotic bacteria from fermented foods and dairy products. Most of the identified probiotic strains belong to the lactic acid bacteria group and the genus Bifidobacterium. However, current molecular-based knowledge has allowed the identification and culture of obligatory anaerobic commensal bacteria from the human gut, such as Akkermansia spp. and Faecalibacterium spp., among other human symbionts. We are aware that the identification of new strains of these species does not guarantee their probiotic effects and that each effect must be proved through in vitro and in vivo preclinical studies before clinical trials (before even considering it as a probiotic strain). In most cases, the identification and characterization of new probiotic strain candidates may lack the appropriate set of in vitro experiments allowing the next assessment steps. Here, we address some innovative strategies reported in the literature as alternatives to classical characterization: (i) identification of alternatives using whole-metagenome shotgun sequencing, metabolomics, and multi-omics analysis; and (ii) probiotic characterization based on molecular effectors and/or traits to target specific diseases (i.e., inflammatory bowel diseases, colorectal cancer, allergies, among others).

Lactic acid bacteria: isolation-characterization approaches and industrial applications

The current state-of-art research pertaining to lactic acid bacteria (LAB) calls for the screening and isolation of robust LAB strains to achieve holistic exploitation of LAB and their metabolites of marketable importance. Hence it is imperative to comprehend LAB sources, growth requisites, isolation and characterization strategies necessary for featured cataloging and appropriate culturing. This review comprehensively describes various growth media and biomasses used for supporting LAB sustenance, assay procedures needed for the isolation and characterization of LAB strains, and their application in diverse sectors. The various industrial patents and their summarized claims about novel LAB strains isolated and identified, methods and media (used for detection/screening, isolation, adaptation, culturing, preservation, growth improvement), the techniques and/or methodologies supporting LAB fermentation, and applications of produced industrial metabolites in various market scenarios are detailed.

Vitamin B12 biofortification of soymilk through optimized fermentation with extracellular B12 producing Lactobacillus isolates of human fecal origin

The present study was designed to bio-fortify the soymilk (per se a B12-free plant food matrix). The PCR-based screening characterized the human fecal samples (4 out of 15 tested) and correspondingly identified novel lactobacilli isolates (n = 4) for their B12 production potential and rest (n = 62) as negative for this attribute. Further, 3 out of the 4 selected strains showed ability for extracellular vitamin production. The most prolific strain, Lactobacillus reuteri F2, secreted B12 (132.2 ± 1.9 μg/L) in cobalamin-free-medium with the highest ratio ever reported (0.97:1.00; extra-: intra-cellular). In next stage, the soymilk was biofortified in situ with B12 during un-optimized (2.8 ± 0.3 μg/L) and optimized (156.2 ± 3.6 μg/L) fermentations with a ∼54-fold increase at Artificial Neuro Fuzzy Inference System based R value of >0.99. The added-nutrients, temperature and initial-pH were observed to be the most important fermentation variables for maximal B12 biofortification. We report Lactobacillus rhamnosus F5 as the first B12 producing (101.7 ± 3.4 μg/L) strain from this species. The cyanocobalamin was extracted, purified and separated on UFLC as nutritionally-relevant B12. Besides, the vitamin was bioavailable in an auxotrophic-mutant. The lactobacilli fermentation is suggested, therefore, as an effective approach for B12 biofortification of soymilk.

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PCR-based real-time screening of human fecal samples for the presence of B12-related cbiK gene.

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Novel report of B12 production in Lactobacillus rhamnosus species (strain F5).

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A rare B12-producing phenotype of Lactobacillus reuteri F2 with highest ever ratio of extracellular vs total B12 (0.95:1.0).

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Sequential optimization (OFAT .→ GSD → ANFIS) enhanced post-fermentation soymilk B12 levels by 54-folds.

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One serving size (100 mL) of L. reuteri F2-biofortified fermented soymilk offered 6.5-fold higher B12 than human RDA.

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The produced B12 form is nutritionally-relevant and biologically active for humans.

Conjugal Transfer of Antibiotic Resistances in Lactobacillus spp

Lactic acid bacteria (LAB) are a heterogeneous group of bacteria which are Gram-positive, facultative anaerobes and non-motile, non-spore forming, with varied shapes from cocci to coccobacilli and bacilli. Lactobacillus is the largest and most widely used bacterial species amongst LAB in fermented foods and beverages. The genus is a common member of human gut microbiome. Several species are known to provide benefits to the human gut via synergistic interactions with the gut microbiome and their ability to survive the gut environment. This ability to confer positive health effects provide them a status of generally recognized as safe (GRAS) microorganisms. Due to their various beneficial characteristics, other factors such as their resistance acquisition were overlooked. Overuse of antibiotics has made certain bacteria develop resistance against these drugs. Antibiotic resistance was found to be acquired mainly through conjugation which is a type of lateral gene transfer. Several in vitro methods of conjugation have been discussed previously depending on their success to transfer resistance. In this review, we have addressed methods that are employed to study the transfer of resistance genes using the conjugation phenomenon in lactobacilli.

Identification of Bile Salt Hydrolase and Bile Salt Resistance in a Probiotic Bacterium Lactobacillus gasseri JCM1131T

Lactobacillus gasseri is one of the most likely probiotic candidates among many Lactobacillus species. Although bile salt resistance has been defined as an important criterion for selection of probiotic candidates since it allows probiotic bacteria to survive in the gut, both its capability and its related enzyme, bile salt hydrolase (BSH), in L. gasseri is still largely unknown. Here, we report that the well-known probiotic bacterium L. gasseri JCM1131^T possesses BSH activity and bile salt resistance capability. Indeed, this strain apparently showed BSH activity on the plate assay and highly tolerated the primary bile salts and even taurine-conjugated secondary bile salt. We further isolated a putative BSH enzyme (LagBSH) from strain JCM1131^T and characterized the enzymatic function. The purified LagBSH protein exhibited quite high deconjugation activity for taurocholic acid and taurochenodeoxycholic acid. The lagBSH gene was constitutively expressed in strain JCM1131^T, suggesting that LagBSH likely contributes to bile salt resistance of the strain and may be associated with survival capability of strain JCM1131^T within the human intestine by bile detoxification. Thus, this study first demonstrated the bile salt resistance and its responsible enzyme (BSH) activity in strain JCM1131^T, which further supports the importance of the typical lactic acid bacterium as probiotics.

Technological and Functional Assessment of Riboflavin Enriched Probiotic SoyCurd

Preparation of soymilk-based product with probiotics is reasonably a novel approach in the field of fermented functional foods. The aim of this study was to develop riboflavin enriched fermented soy curds with either or combination of the two riboflavin producing probiotic strains of Lactobacillus plantarum i.e., MTCC 25432 (BBC32B) and MTCC 25433 (BBC33), and to compare the technological and functional properties of its developed products. Acidification rate and lactic acid production were enhanced with L. plantarum and its combination in a shorter time to reach pH 4.7. Hardness and cohesiveness were significantly (p < 0.05) higher for fermented soymilk by co-culture of L. plantarum followed by individual strains. Similarly, higher G′ (6.25 × 102 Pa), G” (2.30 × 103 Pa) and G* (8.00 × 102 Pa) values observed for the combination of both L. plantarum strains showed that the gel formed was firmer and had solid character. The riboflavin content of product developed with a combination of test cultures was significantly higher (342.11 µg/L) than individual cultures and control. The final product had a higher probiotic count (more than 9 log cfu/mL), which is also required for functional food containing probiotics.

In Vitro Evaluation of Probiotic Properties of Lactobacillus plantarum UBLP40 Isolated from Traditional Indigenous Fermented Food

In this study, traditional indigenous fermented food isolate Lactobacillus plantarum UBLP40 was screened for in vitro probiotic properties, antibiotic susceptibility, hemolytic activity, production of lactic acid, hydrogen peroxide, bile salt hydrolase and phytase, and antioxidative activity. Results showed that Lact. plantarum UBLP40 can survive simulated gastrointestinal conditions, adhere to mucin, possess a hydrophobic cell surface, ability to auto-aggregation, and possessed antimicrobial activity against Micrococcus luteus MTCC 106, methicillin-resistant Staphylococcus aureus subsp. aureus ATCC® BAA-1720, Pseudomonas aeruginosa MTCC 1688, and Escherichia coli MTCC 1687. Lact. plantarum UBLP40 produced 48.59 U/mg phytase and 1.78 ± 0.01 gm % lactic acid and showed the ability to produce hydrogen peroxide and bile salt hydrolase. Moreover, the usual antibiotic susceptible profile and non-hemolytic activity indicated the safety of the strain. The intracellular extract of UBLP40 showed 13.8 ± 1.4% (equivalent to ~8 µM butylated hydroxytoluene) α,α-diphenyl-β-picrylhydrazyl (DPPH) radical scavenging activity, reducing activity equivalent to 1 µg L-cysteine, Fe²⁺ chelation equivalent to 5 µM ethylenediaminetetraacetic acid, and exhibited 17.73 ± 4.40 µM glutathione per gram of protein. In conclusion, this study demonstrates that Lact. plantarum UBLP40 is a potential probiotic candidate.

Comparative accounts of probiotic properties of spore and vegetative cells of Bacillus clausii UBBC07 and in silico analysis of probiotic function

In this study, the spores and vegetative cells of B. clausii were independently evaluated for probiotic properties such as acid, gastric juice, bile, and intestinal fluid tolerance, adhesion to solvents/mucin and zeta potential. In addition, in silico identification of genome features contributing to probiotic properties were investigated. The results showed that spores were highly stable at gastric acidity and capable to germinate and multiply under intestinal conditions as compared to vegetative cells. The higher hydrophobicity of spores, compared to vegetative cells, is advantageous for colonization and persistence in the intestine. Furthermore, the presence of F ₀ F ₁ ATP synthase, amino acid decarboxylase, bile acid symporter, mucin/collagen/fibronectin-binding proteins, heat/cold shock proteins, and universal stress proteins suggests that the strain is able to survive stress. In conclusion, the results demonstrate that B. clausii UBBC07 spores show significantly higher survival and adhesion in in vitro gastrointestinal conditions as compared to vegetative cells. Besides, this study provides a comparative analysis of the in vitro probiotic properties of spores and vegetative cells of Bacillus clausii UBBC07.