Fermented Milk Samples Research Articles

Culturomics: A promising approach for exploring bacterial diversity in natural fermented milk

Natural fermented milk is an abundant source of microbial resources, some of which possess probiotic properties that can help prevent and treat human diseases. However, many potential probiotics have not yet been isolated using traditional pure-culture methods. Culturomics, a relatively novel approach, can be primarily employed to cultivate and identify previously unknown and uncultured bacteria. Nevertheless, their application in natural fermented milk remains limited. Therefore, the primary objective of this study was to evaluate the bacterial diversity in natural fermented milk and explore its microbial potential. For this purpose, we collected three natural fermented milk samples from Inner Mongolia and subjected them to enrichment culture in blood culture bottles for 14 d. Bacterial isolates were obtained from the samples at 0, 3, 7, and 14 days using two culture temperatures and four media, and full-length 16S rRNA gene sequencing was performed for each sample at each time point. The results revealed that 488 strains were isolated from three samples belonging to 3 phyla, 11 genera, and 27 species. The method using two culture temperatures (20 °C and 30 °C) and two media (MRS and RCM + Vb) yielded most of the isolates after 3, 7, and 14 days of enrichment culture. Furthermore, full-length 16S rRNA gene sequencing confirmed that this method significantly increased bacterial diversity in natural fermented milk. In conclusion, the culturomics method demonstrates great potential for the isolation of a greater number of bacterial species and is advantageous for further exploration of the diversity of culturable microorganisms in natural fermented milk.

Identification, Safety Assessment, and Antimicrobial Characteristics of Cocci Lactic Acid Bacteria Isolated from Traditional Egyptian Dairy Products.

The main objective of this study is to isolate and identify lactic acid bacteria (LAB) from various Egyptian dairy products, examine their antibacterial and hemolysis potential, and ensure their safety when used as starter cultures in different dairy industries. Egyptian dairy products are often made without the use of commercial starter cultures, using raw milk and artisanal methods. The most popular traditional dairy products are Laban Rayeb and Zabady, as well as the cheese varieties of Ras, Domiati, and Karish. The microbial communities used for fermentation and the diversity of lactic acid bacteria are the most important factors that can affect the quality of these products. In order to investigate the diversity of cocci lactic acid bacteria in Egyptian dairy products, 70 samples of raw or fermented milk and cheeses were collected from traditional cheese-making factories, local markets, and farmhouses located in the Delta area of Egypt. Following this, the LAB were isolated from the samples. One hundred fifty-seven isolates of Gram-positive, catalase-negative, and cocci bacterial species were identified via rep-PCR, and some isolates were confirmed using pheS and 16S rRNA gene sequencing, as follows: Streptococcus infantarius subsp. infantarius (three isolates), Enterococcus hirae (three isolates), Enterococcus faecium (ninety-six isolates), Enterococcus faecalis (forty isolates), Enterococcus durans (six isolates), Lactococcus garvieae (one isolate), Pediococcus acidilactici (seven isolates), and Lactococcus lactis subsp. Lactis (one isolate). These findings validate that five strains have strong antibacterial activity against Escherichia coli, Salmonella typhimurium, and Listeria monocytogenes, and one hundred thirty-four strains were safe for hemolysis. The five strains were selected as protective cultures, including Pediococcus acidilactici, Lactococcus lactis subsp. lactis, E. faecalis, and E. faecium.

A Novel C-Terminal Truncated Bacteriocin Found by Comparison between Leuconostoc mesenteroides 406 and 213M0 Isolated from Mongolian Traditional Fermented Milk, Airag.

Bacteriocins produced by lactic acid bacteria are known to be useful tools for food biopreservation and fermentation control. Leuconostoc mesenteroides subsp. mesenteroides 406 and 213M0 isolated from different samples of Mongolian traditional fermented milk, airag, had been reported to produce listericidal bacteriocin-like inhibitory substances with similar but slightly different properties. In this study, the antibacterial properties and the related gene sequences of both strains were compared, and then their bacteriocins were purified and identified. Strain 406 was superior to strain 213M0 in cell growth and antibacterial activity against many strains. However, the activity of 213M0 was stronger than that of 406 against a few strains. DNA sequencing revealed two and three plasmids in 406 and 213M0, respectively, and each one of them harbored an almost identical mesentericin Y105-B105 gene cluster. Removal of these plasmids resulted in a complete loss of activity, indicating that the antibacterial activity of both strains was generated by bacteriocins encoded on the plasmids. Mesentericins Y105 and B105 were purified from both cultures, and another novel bacteriocin, named mesentericin M, was identified from the 213M0 culture only. Its structural gene was coded on a 213M0 plasmid and, surprisingly, its C-terminal three amino acid residues were post-translationally cleaved. To our knowledge, this is the first report of a C-terminal truncated bacteriocin. In conclusion, the novel bacteriocin should be mainly responsible for the difference in antibacterial properties between the two strains.

The interaction between Lactobacillus delbrueckii ssp. bulgaricus M-58 and Streptococcus thermophilus S10 can enhance the texture and flavor profile of fermented milk: Insights from metabolomics analysis

Lactobacillus delbrueckii ssp. bulgaricus M-58 (M58) and Streptococcus thermophilus S10 (S10) are both dairy starter strains known for their favorable fermentation characteristics. Therefore, this research aimed to study the effects of 1-d low-temperature ripening on the physicochemical properties and metabolomics of fermented milk. Initially, the performance of single (M58 or S10) and dual (M58+S10) strain fermentation was assessed, revealing that the M58+S10 combination resulted in a shortened fermentation time, a stable gel structure, and desirable viscosity, suggesting positive strain interactions. Subsequently, nontargeted metabolomics analyses using liquid chromatography-MS and GC-MS were performed to comparatively analyze M58+S10 fermented milk samples collected at the end of fermentation and after 1 d of low-temperature ripening. The results showed a significant increase in almost all small peptides and dodecanedioic acid in the samples after 1 d of ripening, although there was a substantial decrease in indole and amino acid metabolites. Moreover, notable increases were observed in high-quality flavor compounds, such as geraniol, delta-nonalactone, 1-hexanol,2-ethyl-, methyl jasmonate, and undecanal. This study provides valuable insights into the fermentation characteristics of the dual bacterial starter consisting of M58 and S10 strains and highlights the specific contribution of the low-temperature ripening step to the overall quality of fermented milk.

Screening of lactic acid bacteria with the ability to reduce goaty flavor related fatty acids in goat milk

In this study, we conducted sensory evaluation and gas chromatography–mass spectrometry analysis on fermented goat milk samples prepared by 12 strains of lactic acid bacteria (LAB) isolated from goat milk to screen for strains with the ability to reduce the goaty flavor. The bacterial counts of fermented goat milk was 7.07–9.01 log CFU/mL. The electronic nose distinguished fresh goat milk (FGM) and fermented goat milk, and the electronic tongue results showed that Leuconostoc citreum 1, 4, 20, 22, 32, and 57, Latilactobacillus curvatus 144 and 147 imparted fermented goat milk a taste different from FGM. Overall, Leuconostoc citreum 57, Leuconostoc citreum 126, Latilactobacillus curvatus 142, Latilactobacillus curvatus 143, and Latilactobacillus curvatus 147 were screened with the ability to improve the flavor of goat milk. They gave fermented goat milk a goat flavor score lower than or equal to FGM. And the fermented goat milk samples 57, 126, 142, 143, and 147 contained 25, 22, 15, 24, and 17 volatile flavor compounds, respectively, with a greater variety and content of ketones and aldehydes and lower levels of hexanoic acid, octanoic acid, and decanoic acid than FGM. However, the pH and WHC results indicated that the application of these strains as secondary cultures is necessary. Our finding provides basic research data to improve the flavor of goat milk products.

Exploring prebiotic properties and its probiotic potential of new formulations of soy milk-derived beverages.

The food and beverage industry has shown a growing interest in plant-based beverages as alternatives to traditional milk consumption. Soy milk is derived from soy beans and contains proteins, isoflavones, soy bean oligosaccharides, and saponins, among other ingredients. Because of its high nutritive value and versatility, soy milk has gained a lot of attention as a functional food. The present work aims to explore the prebiotic properties and gastrointestinal tolerance potential of new formulations of soy milk-derived drinks to be fermented with riboflavin-producing probiotic Lactiplantibacillus plantarum MTCC (Microbial Type Culture Collection and Gene Bank) 25432, Lactiplantibacillus plantarum MTCC 25433, and Lactobacillus acidophilus NCIM (National Collection of Industrial Microorganisms) 2902 strains. The soy milk co-fermented beverage showed highest PAS (1.24 ± 0.02) followed by soy milk beverages fermented with L. plantarum MTCC 25433 (0.753 ± 0.0) when compared to the commercial prebiotic raffinose (1.29 ± 0.01). The findings of this study suggested that the soy milk beverages exhibited potent prebiotic activity, having the ability to support the growth of probiotics, and the potential to raise the content of several bioactive substances. The higher prebiotics activity score showed that the higher the growth rate of probiotics microorganism, the lower the growth of pathogen. For acidic tolerance, all fermented soy milk managed to meet the minimal requirement of 106 viable probiotic cells per milliliter at pH 2 (8.13, 8.26, 8.30, and 8.45 logs CFU/mL, respectively) and pH 3.5 (8.11, 8.07, 8.39, and 9.01 log CFU/mL, respectively). The survival rate of soy milk LAB isolates on bile for 3 h ranged from 84.64 to 89.60%. The study concluded that lactobacilli could thrive in gastrointestinal tract. The sensory evaluation scores for body and texture, color, flavor, and overall acceptability showed a significant difference (p < 0.05) between the fermented probiotic soy milk and control samples. Soy milk fermented with a combination of L. plantarum MTCC 25432 & MTCC 25433 demonstrated the highest acceptability with the least amount of beany flavor. The findings of the study suggest soy milk's potential in plant-based beverage market.

Shotgun metagenomic analysis of microbiota dynamics during long-term backslopping fermentation of traditional fermented milk in a controlled laboratory environment

Traditional fermented milks are produced through an inoculation process that involves the deliberate introduction of microorganisms that have been adapted and perpetuated across successive generations. However, the changes in the microbiota of traditional fermented milk during long-term inoculation fermentation in a laboratory environment remain unclear. In this study, we collected 5 samples of traditional fermented milk samples from 5 different counties in Tibet (3 kurut products) and Xinjiang (2 tarag products) of China, which served as starter cultures for a 9-mo continuous inoculation fermentation experiment. We analyzed the inter- and intra-population variations in the microbial communities of the collected samples, representing their macrodiversity and microdiversity, using shotgun metagenomic sequencing. Across all samples, we obtained a total of 186 high-quality metagenomic-assembled genomes, including 7 genera and 13 species with a relative abundance of more than 1%. The majority of these genomes were annotated as Lactobacillus helveticus (60.46%), Enterococcus durans (9.52%), and Limosilactobacillus fermentum (6.23%). We observed significant differences in species composition and abundance among the 5 initial inoculants. During the long-term inoculation fermentation, we found an overall increasing trend in species diversity, composition, and abundances of carbohydrate metabolism module-encoding genes in the fermented milk bacterial metagenome, while the fermented milk virome exhibited a relatively narrow range of variation. Lactobacillus helveticus, a dominant species in traditional fermented milk, displayed high stability during the long-term inoculation fermentation. Our study provides valuable insights for the industrial production of traditional fermented milk.

Natural deep eutectic solvent-supported exfoliated graphite nanoplatelet-based electrochemical sensor for the determination of tyramine in fermented beverages

A novel electrochemical sensor was developed for the determination of tyramine. The sensor was constructed by modifying the surface of a glassy carbon electrode (GCE) with a film composed of exfoliated graphite nanoplatelets (xGnPs) dispersed in a natural deep eutectic solvent (NADES). The NADES was prepared by simply mixing equimolar amounts of caprylic acid and menthol and heating at 80 °C for 30 minutes. Characterization studies confirmed the formation of a NADES through the attenuated total reflectance-Fourier transform infrared spectroscopy technique, while transmission electron microscopy demonstrated the ability of the NADES to disperse the xGnPs. Electrochemical impedance spectroscopy data showed that the modified sensor exhibited lower resistivity than the unmodified electrode. By optimizing the parameters of square wave voltammetry and experimental conditions to obtain the highest peak current values for tyramine oxidation, a calibration curve was constructed in a 0.1 mol L−1 phosphate buffer (pH 7.0), obtaining detection and quantification limits of 0.06 and 0.20 mg L−1, respectively. Finally, the sensor was successfully applied to the determination of tyramine in fermented milk, beer, and non-alcoholic beer samples, with satisfactory recovery data.

Probiotic yoghurt-like fermented milk product enriched with Lactobacillus desidiosus and Lactobacillus fermentum: proximate composition, physicochemical, microbiological, and sensory evaluation during refrigerated storage

The combination of multiple strains and multiple species in lactic acid bacteria-based fermented milk offers the potential for nutritional and sensory attributes, making it an attractive option for developing high-quality and health-promoting probiotic yoghurt-like fermented milk products. In the present study, four combinations of yoghurt-like fermented milk samples: Sample 1 (Control), Sample 2 (Lactobacillus desidiosus), Sample 3 (Lactobacillus fermentum), and Sample 4 (Lactobacillus desidiosus and Lactobacillus fermentum) were developed. Proximate composition (moisture, ash, protein, fat, carbohydrate), physicochemical (pH, titratable acidity, syneresis, total soluble sloid), microbiological (Lactobacillus bacteria, yeast and mold, and coliform bacteria), and sensory properties (color, flavor, texture, taste, and overall acceptability) were assessed under refrigerator conditions (4 °C) from 0 to 28 days of storage period. Proximate composition differed significantly (p < 0.05) among samples for moisture (49.34–79.32%), ash (1.14–0.31%), protein (3.72–3.21%), fat (11.23–5.62%), and carbohydrate (33.11–12.98%). Yoghurt-like fermented milk containing Lactobacillus desidiosus as single or in combination with Lactobacillus fermentum resulted in reduced pH levels (6.02–3.49), total soluble solid (41.66–24.66%) and increased syneresis (30.04–65.52%), titratable acidity content (0.42–1.62%). Single or combination of Lactobacillus desidiosus and Lactobacillus fermentum significantly (p < 0.05) reduced Lactobacillus bacteria (8.17–6.01 Log CFU/g), yeast, and mold (1.45–1.19 Log CFU/g). Additionally, none of the samples of probiotic yoghurt-like fermented milk showed any detectable coliform count, indicating the possibility of prolonging the shelf life. The sample prepared by Lactobacillus desidiosus had the highest sensory ranking (8.10) at day 0 and during storage than other samples. In conclusion, the inclusion of Lactobacillus desidiosus and Lactobacillus fermentum strains in the composition of production starter cultures holds great promise. The utilization of these enriched starter cultures enables the production of healthy food products that maintain their quality throughout the entire storage period.

Detection of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus in Inactivated Fermented Milk Using Fluorescence Quantitative Loop-Mediated Isothermal Amplification

Currently, no effective method exists to detect and monitor fermentation probiotics and evaluate the quality of inactivated fermented milk. Therefore, in this study, a fluorescence quantitative loop-mediated isothermal amplification (FQ-LAMP) method was developed to detect Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus. The specificity of LAMP primers for L. bulgaricus and S. thermophilus was verified using S-type amplification curves and a single peak at approximately 88.568°C and 83.704°C of the melting curves, respectively. The lowest quantification limits of FQ-LAMP for the two strains in inactivated fermented milk were 8.1 × 103 CFU/g (170 fg/μL) and 6.8 × 103 CFU/g (170 fg/μL), respectively. FQ-LAMP was used to analyse 40 inactivated fermented milk samples from six randomly selected brands. The logarithmic concentration of S. thermophilus in all products was between 7.482 and 8.936. The logarithmic concentration of L. bulgaricus ranged from 4.590 to 8.277, with no detectable L. bulgaricus in three samples. FQ-LAMP has the potential as a rapid, specific, and accurate method for detecting and monitoring L. bulgaricus and S. thermophilus in inactivated fermented milk during their shelf life.

Isolation, molecular characterization and antibiogram of Lactic acid bacteria from dairy cattle sources of Mizoram, India

A total of 250 samples of dairy cattle sources comprised of 100 cattle faeces, 75 raw milk, and 75 fermented milk samples which were randomly collected from different areas of Aizawl district of Mizoram that have been analyzed bacteriologically for enumeration and isolation of Lactic acid bacteria (LAB). The 90 phenotypically positive LAB isolates were further analyzed molecularly by 16S-rRNA gene analysis and 42 isolates were found positive. A total of 20 PCR positive LAB isolates were randomly selected and sequenced, out of which 11 isolates were positive for LAB after sequence analysis, belonging to six species of LAB, namely Lactibantibacillus plantarum (4), Lactobacillus fermentum (2), Lactobacillus brevis (2), Bacillus coagulance (1), Enterococcus faecium (1) and Weissella cibaria (1). The phylogenetic tree was constructed to check the relatedness of the strains with other referral LAB strains from NCBI gene bank. These 11 isolates were further analyzed for antibiogram. All 11 LAB strains tested for antibiotic sensitivity were 100% resistant to kanamycin, whereas intermediate resistance was shown by Lactobacillus brevis FM046 to clindamycin and three strains namely Lactobacillus fermentum FM011, Bacillus coagulans FM033 and Lactobacillus brevis FM046 to penicillin. All the 11 LAB strains were 100% sensitive to most of the tested antibiotics namely amikacin, ampicillin, azithromycin, cefoxitin, cefpodoxime, ceftriaxone, erythromycin, gentamicin and rifampicin. The LAB strains detected from the dairy cattle sources of Mizoram with sensitive antibiogram might be further studied for their probiotic potential.

Formulation of Culture Medium for the Enumeration of Lactic Streptococci and Lactobacilli from Fermented Milk Products

Aims: The present study is focused to formulate a single selective differential medium for the enumeration of mixed lactic flora such as lactic streptococci and lactobacilli in domestic and market fermented milk products.&#x0D; Study Design: In order to enumerate lactic streptococci and lactobacilli in a mixed flora of fermented milk, formulation of single selective medium was optimized using inhibitors and indicator instead of separate selective medium for lactic streptococci and lactobacilli.&#x0D; Place and Duration of Study: The present study was conducted in the Department of dairy Microbiology, Dairy Science College, Karnataka Veterinary, Animal and Fisheries Sciences University (KVAFSU), Hebbal, Bengaluru-24, Karnataka from February 2020 to February 2021.&#x0D; Methodology: Fermented milk samples like curd, yoghurt were collected, serially diluted and pour plated using Readymade M17 and MRS agar media and formulated selective yeast glucose agar medium. Lactic colonies obtained were enumerated, expressed as log10cfu/g and critical difference was calculated to declare significance and non-significance among the microbial parameters.&#x0D; Results: Readymade M17 and MRS agar media gave better recovery of viable cells of lactic streptococci and lactobacilli from market samples of curd, yoghurt and domestic curd samples. The study helped to convert a general purpose medium yeast glucose agar as selective differential medium with addition of calcium propionate of 0.8 per cent to avoid Bacillus spore formers and sodium benzoate of 1.2 per cent to inhibit yeast, the common contaminants in fermented milk with 0.05 per cent BCP that led to formation of purple colonies of lactic streptococci and yellow colonies of lactobacilli.&#x0D; Conclusion: The selective yeast glucose agar with 0.8 per cent and sodium benzoate of 1.2 per cent with 0.05 per cent BCP with purple colonies of lactic streptococci and yellow colonies of lactobacilli can be successfully used. This study verified the enumeration of mixed lactic flora in fermented milk products instead of M17 medium for lactic streptococci and MRS for lactobacilli, separately.

Sensory-directed characterization of key odor-active compounds in fermented milk

The present study aimed to investigate the key odor-active compounds in fermented milk by sensory-directed analysis. Sensory evaluation demonstrated that the overall odor attributes of fermented milk samples were mainly milky, sweet, sour, and buttery. A total of 35 odor compounds were detected in fermented milk samples by dynamic headspace sampling (DHS) combined with gas chromatography–mass spectrometry analysis (GC–MS). Of them, 21 odor-active compounds were detected by GC–MS in combination with olfactometry (O). In addition, 10 key odor-active compounds were screened by DHDA (flavor dilution (FD) factors, FD ≥ 27), odor activity value (OAV) calculation (OAV ≥ 1) and recombination experiments, including 2,3-butanedione, 2,3-pentanedione, 2-heptanone, 2-undecanone, acetic acid, butanoic acid, hexanoic acid, hexanal, nonanal, and 2-pentylfuran. This study provides a basis for subsequent flavor studies of fermented milk and provides theoretical guidance for quality control of fermented milk.

Fatty Acid Profiles Change and the Volatile Organic Compounds Formation During the Cow’S Milk Fermentation with Probiotic &lt;i&gt;Lacticaseibacillus paracasei&lt;/i&gt; Strains

In this work, a comparative analysis of the profile of fatty acids (FA) and volatile organic compounds (VOCs) for skimmed cow’s milk fermented by four different probiotic strains of Lacticasibacillus paracasei (ABK, KF1, MA2 and MA3) was carried out. Analysis of FA and VOC profiles was performed using gas chromatography with mass spectrometric detection (GC-MS). For additional visualization of odor changes and its intensity in the fermented milk samples, the E-nose “electronic nose” odor analyzer was used. In total, presence of 42 different FA was detected in all samples, of which 17 were saturated, 8 monounsaturated, and 5 polyunsaturated. The strain-specific differences between the studied samples were of a complex nature and could not be explained only by the variation in the contribution of several individual FAs. The FA-nutritional indices, characterizing the nutritional and biological value of the samples, were different for milk fermented by different strains. Analysis of VOCs showed that the main odor-forming compounds in the studied samples were FAs and their reaction products, 2-heptanone, 2-nonanone, and 2-nonanol, formed as a result of the following chain of transformations: β-oxidation → decarboxylation → reduction. The aroma of L. paracasei fermentation products, predicted on the basis of the odors of individual VOCs, generally coincided with their organoleptic assessment – a flavor typical of fermented milk (yogurt, curdled milk) with floral and fruity notes.

Revealing the proteolytic characteristics of lactobacillus, lacticaseibacillus, and lactiplantibacillus isolates by in vitro and in situ perspectives

This study examined in vitro and in situ proteolytic characteristics of 8 lactobacilli strains isolated from Turkish Tulum cheese, consisting of L. plantarum, L. helveticus, L. rhamnosus, and L. paracasei, whose beneficial properties and safety concerns previously evaluated. The studied isolates presented versatile proteolytic activity with acidic, neutral, and alkaline proteases. The proteolytic activity of isolates against azocasein substrate was determined between 10.30 and 19.90 U/mg, and L. plantarum isolates had the highest proteolytic activity at varying pH values. Isolates 15, 449, 480 and 675 harboured proteinase genes in the catalytic region of prtR and prtP, and in the prtP/prtM intergenic region. All isolates were also evaluated in the production of fermented milk. As a result of SDS-PAGE analysis of fermented milk samples, L. plantarum isolates 449, 480 and 675 showed more proteolytic activity on milk caseins. Besides, isolate 480 was also effective in hydrolysis of beta-lactoglobulin. L. plantarum isolates resulted in an increase in amino acid (AA) concentrations especially in arginine, alanine, histidine, and proline during the 24-h fermentation of milk. AA production abilities varied depending on the strain. Generally, isolate 675 offered superior AA production ability. The proteolytic properties of cultures are effective on both human health and technological properties of the product in terms of reducing the allergenicity of milk proteins, forming functional peptides, and improving the sensory properties of the product. Based on the results of this study, L. plantarum isolates 449, 480 and 675 could potentially be used as starter cultures or co-cultures for these purposes.

Improving the physicochemical and antioxidative properties of fermented goat milk using carob molasses and some probiotic strains

Fermented goat milk samples, processed by adding 0, 2, and 4% carob molasses, and Bifidobacterium bifidum DSMZ or Lactobacillus helveticus CH5, were evaluated for their physicochemical, antioxidative, and sensory properties along with probiotic viability during storage. pH and viscosity gradually decreased over the storage period whereas their values increased with the increased amount of carob molasses. Bifidobacterium bifidum DSMZ or Lactobacillus helveticus CH5 kept higher viable numbers. Lactobacillus helveticus CH5 strain recorded higher viability. Increasing the added amount of carob molasses increased the total phenolic content, which in turn is reflected in the increase in antioxidant activity. Adding carob molasses participated in the partial masking of the goaty flavor and had no significant effect on the product’s acceptability, which was strongly influenced by the progress of cold storage. Therefore, fermented goat milk described by its enhanced physicochemical and antioxidative properties could be obtained by adding carob molasses and probiotics.

METABOLISM AND FUNCTIONAL HETEROGENEITY OF FERMENTED MILK ORIGIN LACTIC ACID BACTERIA FOR LACTOSE INTOLERANCE

Lactic acid bacteria (LAB) are cosmopolitan in distribution with multiple ecological niches. LAB shows diverse applications in improvement of health by biochemical interference or imuno modulation to overcome several clinical circumstances. Lactose intolerance (LI) is one such situation, where individual show lactose maldigestion after the consumption of dairy products. It is necessary to overcome such a condition by employing indigenous beneficial bacteria or their products. Therefore, in this study we have isolated and characterized LAB from fermented milk samples, from remote villages of districts of south India. Traditionally fermented milk samples (68) were collected, cultivated on MRS medium, identified by biochemical and carbohydrate metabolic activity and correlated with Bergey's manual of systematic bacteriology. When matched with other LAB, Lactiplantibacillus isolates were able to reduced pH of medium significantly and reached pH of 4.6 in 48 hours. On MRS agar, 450 different bacterial isolates were isolated, recognized as presumptive LAB and classified up to the level of genera as Lactiplantibacillus (285), Lactococcus (70), Pediococcus (19), Streptococcus (20), and Enterococcus (16). Later, β-galactosidase screening was carried out using MRS/X-gal agar medium. Out of 450 LAB isolates only Lactiplantibacillus isolates were potential β-galactosidase producers. GRAS organisms such as LAB are multifaceted diverse group of bacteria localized in varieties of fermented foods/in the intestine and recognized as probiotics. Distinct contribution of LAB in health care and disorder management made this organism as a choice for alternate therapy; hence functionality of LAB can be promoted for LI management.

Differences in Aroma Metabolite Profile, Microstructure, and Rheological Properties of Fermented Milk Using Different Cultures.

Texture and flavour are the key attributes determining sensory quality and are highly affected by starter cultures. A selection of phenotypic strains is needed to create diverse texture and flavour to meet consumers' preferences. In this study, the use of five lactic acid bacteria strains in the production of fermented milk, along with the metabolite profiles, microstructure, and rheological properties of the fermented milk samples, was investigated. Our results showed that Lactobacillus helveticus (LH) and Streptococcus thermophilus (ST) had a stronger acidification during fermentation but resulted in products with a coarser protein network compared to Lactococcus lactis (BL1) and Leuconostoc mesenteroides (CL3). Milk fermented by LH had the highest viscosity and exopolysaccharide concentration, while milk fermented by ST had the highest concentration of diacetyl. Although Leuconostoc pseudomesenteroides (CL3ST) had a minimal acidification capability, it produced high levels of ethyl-derived compounds associated with sweet, fruity, and floral fragrances. The results demonstrated that LH and ST could be used as starter cultures targeting fermented milks with different viscosities, while BL1, CL3, and CL3ST are suitable as adjunct cultures to impact different acidic sharpness and flavour notes.

Assessment of Oxytetracycline and Penicillin G Residues Levels in Raw and Fermented Milk in Maiduguri, Northeastern Nigeria

This study was conducted to evaluate the presence and concentration of Oxytetracycline and Penicillin G residues in raw cow and Fermented milk consumed in Maiduguri, Northeastern Nigeria. A total of 172 (86 raw and 86 fermented) milk samples were randomly collected from different milk selling points in Maiduguri. A Spectrophotometer ultraviolet visible spectrum machine was used to detect and quantify the oxytetracycline and penicillin G residues in the milk samples. All samples (raw and fermented milk) tested positive for oxytetracycline and penicillin G residues with a mean residual concentration of 36 µg/L and 20 µg/L in raw and fermented milk respectively for oxytetracycline while the mean residue concentration of penicillin G is 649 µg/L and 397 µg/L in raw and fermented milk respectively. However, the oxytetracycline residues detected were all below the Maximum Residue Level (MRL) standards of 100 µg/L, while the penicillin G residue detected were all above the maximum residue standard of 5 µg/L. The maximum and minimum residue for oxytetracycline detected in raw milk was 79 and 10 (µg/L) respectively while the maximum and minimum residue detected in fermented milk was 42 and 9 (µg/L) respectively. The maximum and minimum residue detected for penicillin G residue in raw milk was 1993 and 767 (µg/L) respectively while the maximum and minimum residue detected in fermented milk was 288 and 164 (µg/L). This study revealed the presence of both oxytetracycline and penicillin G residues in raw and fermented milk consumed in Maiduguri. However, oxytetracycline residues detected in this study were found to be within the acceptable limits, while the penicillin G residues were highly above the MRL standard set by CODEX.

Probiotic potential of β‑galactosidase‑producing lactic acid bacteria from fermented milk and their molecular characterization.

Probiotics have attained significant interest in recent years as a result of their gut microbiome modulation and gastrointestinal health benefits. Numerous fermented foods contain lactic acid bacteria (LAB) which are considered as GRAS and probiotic bacteria. The present study aimed to investigate indigenous LAB from homemade fermented milk samples collected in remote areas of Karnataka (India), in order to isolate the most potent and well-adapted to local environmental conditions bacteria, which were then evaluated using a step-by-step approach focused on the evaluation of probiotic traits and β-galactosidase-producing ability. LAB were screened using 5-bromo-4-chloro-3-indole-D-galactopyranoside (X-Gal) and O-nitrophenyl-β-D-galactopyranoside (ONPG) as substrate, and exhibited β-galactosidase activity ranging from 728.25 to 1,203.32 Miller units. The most promising isolates were selected for 16S rRNA gene sequence analysis and identified as Lactiplantibacillus plantarum, Limosilactobacillus fermentum, Lactiplantibacillus pentosus and Lactiplantibacillus sp. Furthermore, these isolates were evaluated by in vitro, viz., survival in gastrointestinal tract, antibiotic susceptibility, antimicrobial activity, cell surface characteristics, and haemolytic activity. All eight isolates demonstrated strong adherence and prevented pathogen penetration into HT-29 cells, indicating potential of the bacteria to scale up industrial level production of milk products for lactose intolerants.