Identification and characterisation of the lactic acid bacteria associated with the traditional fermentation of dairy fermented product

Dual Role of Probiotic Lactic Acid Bacteria Cultures for Fermentation and Control Pathogenic Bacteria in Fruit-Enriched Fermented Milk

The food industry has been developing new products with health benefits, extended shelf life, and without chemical preservation. Bacteriocin-producing lactic acid bacteria (LAB) strains have been evaluated for food fermentation to prevent contamination and increase shelf life. In this study, potentially probiotic LAB strains, Lactiplantibacillus (Lb.) plantarum ST8Sh, Lacticaseibacillus (Lb.) casei SJRP38, and commercial starter Streptococcus (St.) thermophilus ST080, were evaluated for their production of antimicrobial compounds, lactic acid and enzyme production, carbohydrate assimilation, and susceptibility to antibiotics. The characterization of antimicrobial compounds, the proteolytic activity, and its inhibitory property against Listeria (List.) monocytogenes and Staphylococcus (Staph.) spp. was evaluated in buriti and passion fruit-supplemented fermented milk formulations (FMF) produced with LAB strains. Lb. plantarum ST8Sh was found to inhibit List. monocytogenes through bacteriocin production and produced both L(+) and D(-) lactic acid isomers, while Lb. casei SJRP38 mainly produced L(+) lactic acid. The carbohydrate assimilation profiles were compatible with those usually found in LAB. The potentially probiotic strains were susceptible to streptomycin and tobramycin, while Lb. plantarum ST8Sh was also susceptible to ciprofloxacin. All FMF produced high amounts of L(+) lactic acid and the viability of total lactobacilli remained higher than 8.5 log CFU/mL during monitored storage period. Staph. aureus ATCC 43300 in fermented milk with passion fruit pulp (FMFP) and fermented milk with buriti pulp (FMB), and Staph. epidermidis KACC 13234 in all formulations were completely inhibited after 14 days of storage. The combination of Lb. plantarum ST8Sh and Lb. casei SJRP38 and fruit pulps can provide increased safety and shelf-life for fermented products, and natural food preservation meets the trends of the food market.

Direct Utilization and Conversion of raw Starch to Exopolysaccharides by a newly isolated Amylolytic Streptococcus sp

A newly isolated culture is identified as Streptococcus lutetiensis with significant starch saccharifying activity. Along with considerable amylolytic property (~ 2.71U/mL), the culture exhibited significant production of exopolysaccharide (EPS) in starch medium. Interestingly, the glycosyl transferase activity which is essential in the biosynthesis of polysaccharide is also detected in the culture and after screening and process optimization, a maximum EPS titre of 19.92 ± 0.5g/L was obtained from cassava starch. The crude EPS, after purification and characterization (monosaccharide analysis, FT-IR, TGA, GPC, NMR, and SEM) was found to be of dextran nature with a Mw of 1275.36kDa. Dextran type exopolysaccharide are synthesized by dextransucrase enzyme by the transfer of glucosyl residues from sucrose to dextran polymer. Iinterestingly, the glycosyl transferase enzyme activity which is essential in the biosynthesis of EPS is also detected in the culture. The particle size (447.8 dnm) and the zeta potential (-33.4) analysis of the purified EPS showed that the EPS produced is a stable molecule and has a random coil confirmation when exposed to alkaline condition with shear thinning property. One step conversion of sustainable low-cost starchy raw materials without adding external enzymes for hydrolysis, improved the economic viability of EPS production.

Antimicrobial Resistance of Lactic Acid Bacteria from Nono, a Naturally Fermented Milk Product

BACKGROUND

Antimicrobial resistance (AMR) is one of the biggest threats to public health. The food chain has been recognised as a vehicle for transmitting AMR bacteria. However, information about resistant strains isolated from African traditional fermented foods remains limited. Nono is a traditional, naturally fermented milk product consumed by many pastoral communities across West Africa. The main aim of this study was to investigate and determine the AMR patterns of lactic acid bacteria (LAB) involved in the traditional fermentation of milk for Nono production, and the presence of transferable AMR determinants.

METHODS

One hundred (100) LAB isolates from Nono identified in a previous study as Limosilactobacillus fermentum, Lactobacillus delbrueckii, Streptococcus thermophilus, Streptococcus infantarius, Lentilactobacillus senioris, Leuconostoc pseudomesenteriodes, and Enterococcus thailandicus were investigated. The minimum inhibitory concentration (MIC) was determined for 18 antimicrobials using the micro-broth dilution method. In addition, LAB isolates were screened for 28 antimicrobial resistance genes using PCR. The ability of LAB isolates to transfer tetracycline and streptomycin resistance genes to Enterococcus faecalis was also investigated.

RESULTS

The experiments revealed variable antimicrobial susceptibility according to the LAB isolate and the antimicrobial tested. The tetracycline resistance genes tet(S) and tet(M) were detected in isolates Ent. thailandicus 52 and S. infantarius 10. Additionally, aad(E) encoding resistance to streptomycin was detected in Ent. thailandicus 52. The conjugation experiments suggested that the tet(S) and aad(E) genes were transferable in vitro from isolate Ent. thailandicus 52 to Ent. faecalis JH2-2.

SIGNIFICANCE AND IMPACT

Traditional fermented foods play a significant role in the diet of millions of people in Africa, yet their contribution to the burden of AMR is largely unknown. This study highlights that LAB involved in traditionally fermented foods could be potential reservoirs of AMR. It also underscores the relevant safety issues of Ent. thailandicus 52 and S. infantarius 10 for use as starter cultures as they carry transferable AMR genes. Starter cultures are an essential aspect of improving the safety and quality attributes of African fermented foods. However, AMR monitoring is an important safety aspect in the selection of starter cultures for improving traditional fermentation technologies.

Influence of Different Ratios of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus on Fermentation Characteristics of Yogurt

Lactic acid bacteria (LAB) are industrially important bacteria that are widely used in the fermented food industry, especially in the manufacture of yogurt. The fermentation characteristics of LAB are an important factor affecting the physicochemical properties of yogurts. Here, different ratios of L. delbrueckii subsp. bulgaricus IMAU20312 and S. thermophilus IMAU80809 were compared with a commercial starter JD (control) for their effects on viable cell counts, pH values, titratable acidity (TA), viscosity and water holding capacity (WHC) of milk during fermentation. Sensory evaluation and flavour profiles were also determined at the end of fermentation. All samples had a viable cell count above 5.59 × 10⁷ CFU/mL at the end of fermentation, and a significant increase in TA and decrease in pH were observed. Viscosity, WHC and the sensory evaluation results of one treatment ratio (A3) were closer to the commercial starter control than the others. A total of 63 volatile flavour compounds and 10 odour-active (OAVs) compounds were detected in all treatment ratios and the control according to the results from solid-phase micro-extraction-gas chromatography-mass spectrometry (SPME-GC-MS). Principal components analysis (PCA) also indicated that the flavour characteristics of the A3 treatment ratio were closer to the control. These results help us understand how the fermentation characteristics of yogurts are affected by the ratio of L. delbrueckii subsp. bulgaricus to S. thermophilus in starter cultures; this is useful for the development of value-added fermented dairy products.

Screening of a Novel Lactiplantibacillus plantarum MMB-05 and Lacticaseibacillus casei Fermented Sandwich Seaweed Scraps: Chemical Composition, In Vitro Antioxidant, and Volatile Compounds Analysis by GC-IMS

Lactic acid fermentation is a promising method for developing sandwich seaweed scraps. The objectives of this study were to investigate the effect of fermentation with Lactiplantibacillus plantarum MMB-05, Lactiplantibacillus casei FJAT-7928, mixed bacteria (1:1, v/v) and control on the physicochemical indexes, in vitro antioxidant activity, and volatile compounds of Porphyra yezoensis sauce. Sensory evaluation was also performed. The results indicated that all lactic acid bacteria strains grew well in P. yezoensis sauce after 72 h of fermentation, with the viable cell counts of L. plantarum MMB-05 exceeding 10.0 log CFU/mL, the total phenolic content increasing by 16.54%, and the lactic acid content increasing from 0 to 44.38 ± 0.11 mg/mL. Moreover, the metabolism of these strains significantly increased the content of umami, sweet and sour free amino acids in P. yezoensis sauce. The total antioxidant capacity of L. plantarum MMB-05, L. casei FJAT-7928, mix and control groups increased by 594.59%, 386.49%, 410.27%, and 287.62%, respectively. Gas chromatography-ion mobility spectrometry (GC-IMS) analysis suggested that aldehydes and ketones accounted for the largest proportion, and the relative contents of acids and alcohols in P. yezoensis sauce increased significantly after lactic acid bacteria fermentation. In addition, the analysis of dynamic principal component analysis (PCA) and fingerprinting showed that the volatile components of the four treatment methods could be significantly distinguished. Overall, the L. plantarum MMB-05 could be recommended as an appropriate starter for fermentation of sandwich seaweed scraps, which provides a fundamental knowledge for the utilization of sandwiched seaweed scraps.

Functional Fermented Probiotics, Prebiotics, and Synbiotics from Non-Dairy Products: A Perspective from Nutraceutical

The current trend of health-conscious consumers and healthy food habits prompts researchers to explore developing food products with synbiotic benefits. Synbiotic foods have gained popularity in recent years due to their functional, nutritional, physiological, and therapeutic characteristics. Lactose intolerance, dyslipidemia, and allergic milk proteins become the barriers in the development of dairy probiotics. The present scenario of an increase in the demand for vegetarian products leads to a rise in the consumption of non-dairy probiotics. Prebiotics like, resistant starch, inulin, and polyphenols are selectively used by gut microbiota to enhance the selection and colonization of probiotics bacteria. Probiotic's action mechanisms include the production of bacteriocins, peptides, short-chain fatty acids, amino acids, vitamins, and other metabolites. Therefore, this review article explores the alternative sources of probiotics so it will help to an understanding of non-dairy based functional fermented foods for both pro and prebiotics. Dietary fibers in vegetables, fruits, and cereals are one of prospective prebiotics and highlighted the various methods for making non-dairy synbiotics based on dietary fibers, such as microencapsulation, freeze-drying, and spray drying is also addressed.

Functional characterization of α-Gal producing lactic acid bacteria with potential probiotic properties

The possibility of exploiting the human immune response to glycan α-Gal for the control of multiple infectious diseases has been the objective of recent investigations. In this field of research, the strain of Escherichia coli O86:B7 has been at the forefront, but this Gram-negative microorganism presents a safety concern and therefore cannot be considered as a probiotic. To address this challenge, this study explored the identification of novel lactic acid bacteria with a safe history of use, producing α-Gal and having probiotic potential. The lactic acid bacteria were isolated from different traditionally fermented foods (kununn-zaki, kindirmo, and pulque) and were screened for the production of α-Gal and some specific probiotic potential indicators. The results showed that Ten (10) out of forty (40) [25%] of the tested lactic acid bacteria (LAB) produced α-Gal and were identified as Limosilactobacillus fermentum, Levilactobacillus brevis, Agrilactobacillus composti, Lacticaseibacillus paracasei, Leuconostoc mesenteroides and Weissella confusa. Four (4) LAB strains with highest levels of α-Gal were further selected for in vivo study using a mouse model (α1,3GT KO mice) to elucidate the immunological response to α-Gal. The level of anti-α-Gal IgG observed were not significant while the level of anti-α-Gal IgM was lower in comparison to the level elicited by E. coli O86:B7. We concluded that the lactic acid bacteria in this study producing α-Gal have potential probiotic capacity and can be further explored in α-Gal-focused research for both the prevention and treatment of various infectious diseases and probiotic development.

In-Depth Investigation of the Safety of Wooden Shelves Used for Traditional Cheese Ripening

The main goal of this research was to characterize the bacterial diversity of the wooden boards used for aging traditional Sicilian cheeses and to evaluate whether pathogenic bacteria are associated with these surfaces. Eighteen cheese dairy factories producing three traditional cheese typologies (PDO Pecorino Siciliano, PDO Piacentinu Ennese, and Caciocavallo Palermitano) were selected within the region of Sicily. The wooden shelf surfaces were sampled by a destructive method to detach wood splinters as well as by a nondestructive brushing to collect microbial cells. Scanning electron microscopy showed the presence of almost continuous bacterial formations on the majority of the shelves analyzed. Yeasts and fungal hyphae were also visualized, indicating the complexity of the plank communities. The amplicon library of the 16S rRNA gene V3-V4 region was paired-end sequenced using the Illumina MiSeq system, allowing the identification of 14 phyla, 32 classes, 52 orders, 93 families, and 137 genera. Staphylococcus equorum was identified from all wooden surfaces, with a maximum abundance of 64.75%. Among cheese-surface-ripening bacteria, Brevibacterium and Corynebacterium were detected in almost all samples. Several halophilic (Halomonas, Tetragenococcus halophilus, Chromohalobacter, Salimicrobium, Marinococcus, Salegentibacter, Haererehalobacter, Marinobacter, and Idiomarinaceae) and moderately halophilic (Salinicoccus, Psychrobacter, and Salinisphaera) bacteria were frequently identified. Lactic acid bacteria (LAB) were present at low percentages in the genera Leuconostoc, Lactococcus, Lactobacillus, Pediococcus, and Streptococcus. The levels of viable microorganisms on the wooden shelves ranged between 2.4 and 7.8 log CFU/cm2. In some cases, LAB were counted at very high levels (8.2 log CFU/cm2). Members of the Enterobacteriaceae family were detected in a viable state for only six samples. Coagulase-positive staphylococci, Salmonella spp., and Listeria monocytogenes were not detected. Seventy-five strains belonged to the genera Leuconostoc, Lactococcus, Pediococcus, Enterococcus, Lactobacillus, and Weissella. IMPORTANCE This study provides evidence for the lack of pathogenic bacteria on the wooden shelves used to ripen internal bacterially ripened semihard and hard cheeses produced in Sicily. These three cheeses are not inoculated on their surfaces, and surface ripening is not considered to occur or, at least, does not occur at the same extent as surface-inoculated smear cheeses. Several bacterial groups identified from the wooden shelves are typically associated with smear cheeses, strongly suggesting that PDO Pecorino Siciliano, PDO Piacentinu Ennese, and Caciocavallo Palermitano cheese rind contributes to their final organoleptic profiles.

Probiotic Properties, Prebiotic Fermentability, and GABA-Producing Capacity of Microorganisms Isolated from Mexican Milk Kefir Grains: A Clustering Evaluation for Functional Dairy Food Applications

Isolation and functional characterization of microorganisms are relevant steps for generating starter cultures with functional properties, and more recently, those related to improving mental health. Milk kefir grains have been recently investigated as a source of health-related strains. This study focused on the evaluation of microorganisms from artisanal Mexican milk kefir grains regarding probiotic properties, in vitro fermentability with commercial prebiotics (lactulose, inulin, and citrus pectin), and γ-aminobutyric acid (GABA)-producing capacity. Microorganisms were identified belonging to genera Lactococcus, Lactobacillus, Leuconostoc, and Kluyveromyces. The probiotic properties were assessed by aggregation abilities, antimicrobial activity, antibiotic susceptibility, and resistance to in vitro gastrointestinal digestion, showing a good performance compared with commercial probiotics. Most of isolates maintained a concentration above 6 log colony forming units/mL after the intestinal phase. Specific isolates of Kluyveromyces (BIOTEC009 and BIOTEC010), Leuconostoc (BIOTEC011 and BIOTEC012), and Lactobacillus (BIOTEC014 and BIOTEC15) showed a high fermentability in media supplemented with commercial prebiotics. The capacity to produce GABA was classified as medium for L. lactis BIOTEC006, BIOTEC007, and BIOTEC008; K. lactis BIOTEC009; L. pseudomesenteroides BIOTEC012; and L. kefiri BIOTEC014, and comparable to that obtained for commercial probiotics. Finally, a multivariate approach was performed, allowing the grouping of 2-5 clusters of microorganisms that could be further considered new promising cultures for functional dairy food applications.