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Fermentation is one of the most effective methods of food preservation. Since ancient times, food has been fermented using lactic acid bacteria (LAB). Fermented milk is a very intricate fermentation ecosystem, and the microbial metabolism of fermented milk largely determines its metabolic properties. The two most frequently used dairy starter strains are Streptococcus thermophilus (S. thermophilus) and Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus). To enhance both the culture growth rate and the flavor and quality of the fermented milk, it has long been customary to combine S. thermophilus and L. bulgaricus in milk fermentation due to their mutually beneficial and symbiotic relationship. On the one hand, the symbiotic relationship is reflected by the nutrient co-dependence of the two microbes at the metabolic level. On the other hand, more complex interaction mechanisms, such as quorum sensing between cells, are involved. This review summarizes the application of LAB in fermented dairy products and discusses the symbiotic mechanisms and interactions of milk LAB starter strains from the perspective of nutrient supply and intra- and interspecific quorum sensing. This review provides updated information and knowledge on microbial interactions in a fermented milk ecosystem. HIGHLIGHTS: The symbiotic relationship between Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus is reviewed. Their nutrient co-dependence is discussed. The role of quorum sensing in their interaction is discussed for the first time. This review is of interest to colleagues interested in exploiting LAB starter cultures. [ABSTRACT FROM AUTHOR]

Background. Functional dyspepsia is a common disorder that is difficult to treat and has a significant negative impact on the quality of life of patients. There is growing evidence that small intestinal microbiota plays a certain role in the pathophysiology of functional dyspepsia. Research aim: to study the effect of a product containing lyophilized lactic acid bacteria Lactobacillus delbrueckii subsp. bulgaricus strain 9702 (IMV B-7085) and its metabolic products on the clinical manifestations of the disease and quality of life of patients with functional dyspepsia. Materials and methods. Thirty-seven patients (16 men and 21 women) with functional dyspepsia were included in the study, their average age was (45.9 ± 2.5) years. The score on the Gastrointestinal Symptom Rating Scale was analyzed before treatment, after completing a 15-day course of taking the probiotic additive, which contained Lactobacillus delbrueckii subsp. bulgaricus, and 15 days after the end of the course. The dynamics of quality of life was evaluated based on the analysis of the SF-36 questionnaires, completed by patients before treatment and on day 30 of observation. Statistical calculations were performed using MedCalc® software, version 12.5.0.0. Results. On day 15 of taking the drug and 15 days after the end of the course, a significant (p < 0.05) decrease in the severity of clinical manifestations on the Gastrointestinal Symptom Rating Scale was found compared to the baseline. The analysis of the dynamics of responses to the SF-36 questionnaire revealed a significant increase (p

In the study, in order to develop novel starter cultures, three types of yoghurt were produced with different combinations of autochthonous yoghurt bacteria and the samples were investigated in terms of fermentation, microbiological quality, physicochemical properties (pH, acidity, water-holding capacity, apparent viscosities, and rheological properties), organic and benzoic acid contents, and sensory properties during 28 days. Lactobacillus delbrueckii subsp. bulgaricus content of all samples was between 7.29 and 8.58, and Streptococcus thermophilus content was between 8.03 and 9.02 log CFU/g during storage. Yoghurt type and storage time statistically affected pH, acidity, water-holding capacity, apparent viscosity, rheological properties, organic and benzoic acid content, and some sensory parameters. The general acceptability scores of the probiotic, traditional, exopolysaccharide, and control samples during storage were 8.27, 7.82, 7.53, and 7.47 respectively. Moreover, the results revealed that the strain combinations for probiotic, traditional, and exopolysaccharide yoghurt samples can be used as novel starter cultures for yoghurt production. [ABSTRACT FROM AUTHOR]

Background. Functional dyspepsia is a common disorder that is difficult to treat and has a significant negative impact on the quality of life of patients. There is growing evidence that small intestinal microbiota plays a certain role in the pathophysiology of functional dyspepsia. Research aim: to study the effect of a product containing lyophilized lactic acid bacteria Lactobacillus delbrueckii subsp. bulgaricus strain 9702 (IMV B-7085) and its metabolic products on the clinical manifestations of the disease and quality of life of patients with functional dyspepsia. Materials and methods. Thirty-seven patients (16 men and 21 women) with functional dyspepsia were included in the study, their average age was (45.9 ± 2.5) years. The score on the Gastrointestinal Symptom Rating Scale was analyzed before treatment, after completing a 15-day course of taking the probiotic additive, which contained Lactobacillus delbrueckii subsp. bulgaricus, and 15 days after the end of the course. The dynamics of quality of life was evaluated based on the analysis of the SF-36 questionnaires, completed by patients before treatment and on day 30 of observation. Statistical calculations were performed using MedCalc® software, version 12.5.0.0. Results. On day 15 of taking the drug and 15 days after the end of the course, a significant (p < 0.05) decrease in the severity of clinical manifestations on the Gastrointestinal Symptom Rating Scale was found compared to the baseline. The analysis of the dynamics of responses to the SF-36 questionnaire revealed a significant increase (p < 0.05) on all scales of the physical component of health and a significant increase (p < 0.05) in social functioning on all scales of the psychological component of health on day 30 of observation. Conclusions. Taking a dietary supplement containing Lactobacillus delbrueckii subsp. bulgaricus strain 9702 (IMV B-7085) improves the clinical manifestations of functional dyspepsia, as evidenced by a reduction in the severity of gastrointestinal symptoms and increased quality of life of these patients. [ABSTRACT FROM AUTHOR]

In this work, we evaluated the protective capacity of Spirulina platensis biomass in preserving Lactobacillus del­brueckii subsp. bulgaricus WDCM 00102. The L. bulgaricus strain was freeze-dried in the presence of S. platensis biomass and the freeze-dried samples were then stored at 5 and 25̊C for varying periods. Subsequently, the samples were rehydrated and bacterial plate counts were determined. The results indicate that a concentration of 12% S. platensis biomass was highly effective in preserving L. bulgaricus. Commercial products with higher S. platensis biomass content exhibited greater protective capacity. While S. platensis biomass is well-known for its prebiotic properties, its protective role has not been previously reported or thoroughly explored. This study demonstrates the protective capacity of S. platensis biomass in preserving L. bulgaricus, a strain particularly sensi­tive to preservation processes.

The immune system is affected by the dietary products humans intake. Immune system regulation by nutrition has uses in the clinical context, but it can also benefit healthy populations by delaying or preventing the emergence of immune-mediated chronic illnesses. In this study, the purpose was to describe and compare the modulator effects on the immune system of the routine ingestion of fresh vs. pasteurized yogurt. A unicentral, prospective, randomized, double-blind, parallel group 8-week nutritional study was carried out comparing the ingestion of 125 g of the products in healthy adults three times a day. A complete battery of in vitro tests on the activity of the immune system, processes and phenomena was performed. Exclusive immune-modulatory effects of fresh yogurt with respect to base line were found in terms of increased systemic IgM (primary immune responses), increased synthesis of IFN-gamma upon stimulation (Th1) and increased peripheral T cells (mainly "naive" CD4s). In the three interventions, we observed an increased phagocytic activity and burst test in granulocytes, together with increased secretion of IL-6, IL-1 β and IL-8 (pro-inflammatory) and increased CD16 expression (FcR favoring phagocytosis) in granulocytes. Overall, it is concluded that regardless of bacteria being alive or thermally inactivated, yogurt has common effects on the innate system, but the presence of live bacteria is necessary to achieve a potentiating effect on the specific immune response. [ABSTRACT FROM AUTHOR]

Acute mountain sickness (AMS) is a common ailment in high-altitude areas caused by the body's inadequate adaptation to low-pressure, low-oxygen environments, leading to organ edema, oxidative stress, and impaired intestinal barrier function. The gastrointestinal tract, being the first to be affected by ischemia and hypoxia, is highly susceptible to injury. This study investigates the role of Lactobacillus delbrueckii subsp. bulgaricus in alleviating acute hypoxic-induced intestinal and tissue damage from the perspective of daily consumed lactic acid bacteria. An acute hypoxia mouse model was established to evaluate tissue injury, oxidative stress, inflammatory responses, and intestinal barrier function in various groups of mice. The results indicate that strain 4L3 significantly mitigated brain and lung edema caused by hypoxia, improved colonic tissue damage, and effectively increased the content of tight junction proteins in the ileum, reducing ileal permeability and alleviating mechanical barrier damage in the intestines due to acute hypoxia. Additionally, 4L3 helped to rebalance the intestinal microbiota. In summary, this study found that Lactobacillus delbrueckii subsp. bulgaricus strain 4L3 could alleviate acute intestinal damage caused by hypoxia, thereby reducing hypoxic stress. This suggests that probiotic lactic acid bacteria that exert beneficial effects in the intestines may alleviate acute injury under hypoxic conditions in mice, offering new insights for the prevention and treatment of AMS. [ABSTRACT FROM AUTHOR]

In this work, we evaluated the protective capacity of Spirulina platensis biomass in preserving Lactobacillus delbrueckii subsp. bulgaricus WDCM 00102. The L. bulgaricus strain was freeze-dried in the presence of S. platensis biomass and the freeze-dried samples were then stored at 5 and 25EC for varying periods. Subsequently, the samples were rehydrated and bacterial plate counts were determined. The results indicate that a concentration of 12% S. platensis biomass was highly effective in preserving L. bulgaricus. Commercial products with higher S. platensis biomass content exhibited greater protective capacity. While S. platensis biomass is well-known for its prebiotic properties, its protective role has not been previously reported or thoroughly explored. This study demonstrates the protective capacity of S. platensis biomass in preserving L. bulgaricus, a strain particularly sensitive to preservation processes. [ABSTRACT FROM AUTHOR]

An unstructured mathematical model is proposed to describe the fermentation kinetics of growth, lactic acid production, pH and sugar consumption by Lactobacillus delbrueckii subsp. bulgaricus WDCM 00102 as a function of the buffering capacity and initial dry matter concentration of pretreated biomass of Arthrospira platensis in the culture media. Initially the experimental data of Lactobacillus delbrueckii subsp. bulgaricus WDCM 00102 fermentations in algae-based media with different buffering capacity and dry matter concentration were fitted to a set of primary models. Later the parameters obtained from these models were used to establish mathematical relationships with the independent variables tested. The models were validated with 6 fermentations of Lactobacillus. delbrueckii subsp. bulgaricus WDCM 00102 in different algae-based media. In most cases the proposed models adequately describe the biochemical changes taking place during fermentation and are a promising approach for the formulation of algae-based probiotic foods. [ABSTRACT FROM AUTHOR]

Lactic acid bacteria (LAB) are commonly used probiotics that improve human health in various aspects. We previously reported that yogurt starter strains, Lactobacillus delbrueckii subsp. bulgaricus 2038 and Streptococcus thermophilus 1131, potentially enhance the intestinal epithelial barrier function by inducing the expression of antimicrobial peptides in the small intestine. However, their effects on physical barrier functions remain unknown. In this study, we found that both strains ameliorated the decreased trans-epithelial resistance and the increased permeability of fluorescein isothiocyanate-dextran induced by tumor necrosis factor (TNF)-α and interferon (IFN)-γ in Caco-2 cells. We also demonstrated that LAB prevented a decrease in the expression and disassembly of tight junctions (TJs) induced by TNF-α and IFN-γ. To assess the repair activity of TJs, a calcium switch assay was performed. Both strains were found to promote the reassembly of TJs, and their activity was canceled by the inhibitor of AMP-activated protein kinase (AMPK). Moreover, these strains showed increased AMPK phosphorylation. These observations suggest that the strains ameliorated physical barrier dysfunction via the activation of AMPK. The activities preventing barrier destruction induced by TNF-α and IFN-γ were strain-dependent. Several strains containing L. bulgaricus 2038 and S. thermophilus 1131 significantly suppressed the barrier impairment, and L. bulgaricus 2038 showed the strongest activity among them. Our findings suggest that the intake of L. bulgaricus 2038 and S. thermophilus 1131 is a potential strategy for the prevention and repair of leaky gut. [ABSTRACT FROM AUTHOR]

In this study, the utilization of 16 nitrogen sources of Lactobacillus delbrueckii subsp. bulgaricus B61-3 were determined, and the types and amounts of nitrogen sources that can improve the freeze-drying tolerance of the strain were screened out. More importantly, the effects of nitrogen source modification on the fermentation performance, cell morphology and enzyme activities of freeze-dried powder of the strain were investigated. The results showed that 30 g/L of bovine bone peptone improved the freeze-drying survival rate from 9.68% to 18.90%, and increased fermentation activity by 22.15% compared with the control group. Changed cell size and morphology of the cultured cells of bovine bone peptone were also observed by electron microscope. Cell cultured in bovine bone peptone medium represented a short rod with smooth surface, and the ratio of length to diameter or area to volume decreased significantly (P

[Display omitted] Traditional fermented milks are produced by inoculating technique, which selects well-adapted microorganisms that have been passed on through generations. Few reports have used naturally fermented milks as model ecosystems to investigate the mechanism of formation of intra-species microbial diversity. Here, we isolated and whole-genome-sequenced a total of 717 lactic acid bacterial isolates obtained from 12 independent naturally fermented milks collect from 12 regions across five countries. We further analyzed the within-sample intra-species phylogenies of 214 Lactobacillus helveticus isolates, 97 Lactococcus lactis subsp. lactis isolates, and 325 Lactobacillus delbrueckii subsp. bulgaricus isolates. We observed a high degree of intra-species genomic and functional gene diversity within-/between-sample(s). Single nucleotide polymorphism-based phylogenetic reconstruction revealed great within-sample intra-species heterogeneity, evolving from multiple lineages. Further phylogenetic reconstruction (presence-absence gene profile) revealed within-sample inter-clade functional diversity (based on carbohydrate-active enzyme- and peptidase-encoding genes) in all three investigated species/subspecies. By identifying and mapping clade-specific genes of intra-sample clades of the three species/subspecies to the respective fermented milk metagenome, we found extensive potential inter-/intra-species horizontal gene transfer events. Finally, the microbial composition of the samples is closely linked to the nucleotide diversity of the respective species/subspecies. Overall, our results contribute to the conservation of lactic acid bacteria resources, providing ecological insights into the microbial ecosystem of naturally fermented dairy products. [ABSTRACT FROM AUTHOR]

The present study investigated the suitability of combinations one Streptococcus thermophilus and five Lactobacillus delbrueckii subsp. bulgaricus isolates for industrial yogurt productions. The isolates were selected after a detailed pre-screening procedure based on acidification performances, production of volatile aroma compounds, texture developing properties and sensory evaluations of yogurts made from single cultures. The fermentation profiles of the combinations were investigated by monitoring the small oscillatory rheological parameters and pH reductions during fermentation. The variations in some physical, chemical and organoleptic characteristics of the yogurt samples were also monitored during cold storage at 4 °C for 21 days. Results indicated that all the combinations reduced the milk acidity to pH 4.6 within 4-5 hour at 43 °C. Gelation profiles of the samples were close to each other (close tan d values) with different elastic (G') and loss (G") moduli, indicating that similar chemical bondings took place in gel formation with different levels. All the samples showed a shear-thinning non-Newtonian flow behavior. Total number of starter bacteria was higher than 6 log cfu/mL in each sample after 21 days of storage. The post-acidification rates were also limited (between 4.21-4.37 after 21 days of cold storage). Untrained sensory evaluation panel found no marginal differences between the samples regarding appearance, body and texture, and aroma and flavor of the samples. To conclude, the combinations examined in this study were found to be suitable for commercial yogurt productions. [ABSTRACT FROM AUTHOR]

The applicability of two lactic acid bacterial strains with probiotic potential and bioprotective properties as additions in the starter culture in yogurt fermentation was examined. The studied strains, Lactobacillus delbrueckii subsp. bulgaricus KZM 2-11-3 and Lactiplantibacillus plantarum KC 5-12, inhibited the growth of Kluyveromyces lactis, Kluyveromyces marxianus, and Saccharomyces cerevisiae. The strain L. delbrueckii subsp. bulgaricus KZM 2-11-3 directly inhibited Escherichia coli. The important characteristics for the quality of the yogurt product, such as physicochemical parameters during fermentation and storage, rheological characteristics, and sensory changes during the storage of samples were determined. The yogurt samples with the strains did not differ in most parameters from the control yogurt with the commercial starter. The added strains showed stable viability in the yogurt samples during storage. The yogurt sample with L. delbrueckii subsp. bulgaricus KZM 2-11-3 and the sample with both strains based on the total evaluation were very similar to the control yogurt with the commercial starter. Using these strains as probiotic supplements to enrich the starter cultures in yogurt production will contribute to developing new products with benefits to human health. [ABSTRACT FROM AUTHOR]

Objective: Its eps gene cluster, the antioxidant activity and monosaccharide composition of exopolysaccharides, the expression levels of related genes at different fermentations were analyzed for clarifying the exopolysaccharide biosynthesis mechanism of Lactobacillus delbrueckii subsp. bulgaricus LDB-C1. Results: The comparison analysis of eps gene clusters indicated that the gene clusters present diversity and strain specificity. The crude exopolysaccharides from LDB-C1 exhibited a good antioxidant activity. Compared with glucose, fructose, galactose, and fructooligosaccharide, inulin significantly improved the exopolysaccharide biosynthesis. The structures of EPSs were significantly different under different carbohydrate fermentation conditions. Inulin obviously increased the expressions of most EPS biosynthesis related genes at fermentation 4 h. Conclusion: Inulin accelerated the beginning of the exopolysaccharide production in LDB-C1, and the enzymes promoted by inulin was beneficial for the accumulation of exopolysaccharide at the whole fermentation process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Using ultrasound and pineapple dietary fiber (PPF) to control post-acidification. • Ultrasound and PPF synergistically enhanced antioxidant properties of yogurts. • Ultrasound coupled with PPF led to significant accumulation of free polyphenols. • Incorporating PPF into the ultrasound process reduced whey separation. • Sonication and PPF affected glycerophospholipid and galactose metabolisms. This study investigated the effects of pineapple peel powder with varied chemical profiles and sonication-assisted polyphenol biotransformation during fermentation on the quality characteristics of yogurt products. It aimed at exploring the feasibility of sonication-assisted fermentation to enhance the physicochemical properties, control post-acidification, and improve antioxidant activities in yogurts fortified with polyphenol-rich pineapple peel powder. Targeted analysis showed that polyphenol-rich pineapple dietary fiber obtained by ultrasonication-assisted extraction (NPFU) exhibited the slowest rates of acidification, highest antioxidant capacity, and lowest degree of whey separation at 21.67 %. Sonication pretreatments significantly increased transformation of free phenolic acids derived from pineapple peel fiber during fermentation, particularly increasing the accumulation of ferulic acid, caffeic acid and 5-hydroxyflavone, revealing the positive effects of sonication-mediated fermentation in promoting the hydrolysis of conjugated phenolics into free fractions. Yogurts fortified with pineapple peel fiber displayed significantly higher antioxidant activities (p < 0.05) compared to those with pineapple peel whole powder, corresponding with the increased free phenolics. Non-targeted metabolomics analysis was employed to explore the mechanisms underlying the alleviated post-acidification by sonication-assisted fermentation during storage. Metabolomic profiling revealed that the bioactive components from pineapple peel extract significantly influenced the metabolism pathways of lactic acid bacteria particularly involving galactose metabolism, glycerophospholipid metabolism, closely associated with the acid production of the strains and the regulation of the post-acidification rates of yogurt during storage. These results confirmed the potential of ultrasound-assisted fermentation combined with the addition of pineapple dietary fiber to enhance yogurt quality, providing an innovative tool to develop future yogurt products with high marketability. [ABSTRACT FROM AUTHOR]

Aim This study investigates the individual and combined effects of fermentation parameters for improving cell biomass productivity and the resistance to freezing, freeze-drying, and freeze-dried storage of Lactobacillus delbrueckii subsp. bulgaricus CFL1. Methods and Results Cells were cultivated at different temperatures (42°C and 37°C) and pH values (5.8 and 4.8) and harvested at various growth phases (mid-exponential, deceleration, and stationary growth phases). Specific acidifying activity was determined after fermentation, freezing, freeze-drying, and freeze-dried storage. Multiple regression analyses were performed to identify the effects of fermentation parameters on the specific acidifying activity losses and to generate the corresponding 3D response surfaces. A multiobjective decision approach was applied to optimize biomass productivity and specific acidifying activity. The temperature positively influenced biomass productivity, whereas low pH during growth reduced the loss of specific acidifying activity after freezing and freeze-drying. Furthermore, freeze-drying resistance was favored by increased harvest time. Conclusions Productivity, and freezing and freeze-drying resistances of L. delbrueckii subsp. bulgaricus CFL1 were differentially affected by the fermentation parameters studied. There was no single fermentation condition that improved both productivity and resistance to freezing and freeze-drying. Thus, Pareto fronts were helpful to optimize productivity and resistance, when cells were grown at 42°C, pH 4.8, and harvested at the deceleration phase. [ABSTRACT FROM AUTHOR]

The multiple probiotic characteristics of strain TCI904 isolated in this study from natural fermented milk were investigated using a mouse model. TCI904 was identified as Lactobacillus delbrueckii subsp. bulgaricu (LDB), a well-known lactic acid starter bacterium found in yogurt. TCI904 exhibited an outstanding pancreatic lipase inhibition activity among several strains of lactic acid bacteria in vitro. Its in vivo effects were further studied. In a comparison of mice fed a high-fat diet (HFD) and those fed a HFD combined with TCI904 for 9 weeks, differences were observed in various aspects of health, and the adverse effects of a HFD were prevented in the latter group. TCI904 effectively prevented fat and body weight accumulation without reducing food intake; it also modulated innate immunity and increased the level of IgA in feces, reversing the increased blood sugar and insulin levels and attenuated the hyperlipidemia caused by a HFD. Based on biochemical test data, compared with the HFD group, a HFD combined with TCI904 induced significant lowering of insulin resistance indicator, homeostasis model assessment-insulin resistance (HOMA-IR) and atherogenic indices of plasma (AIP), the atherogenic coefficient (AC) and cardiac risk ratio (CRR) and increased the cardioprotective index (CPI). In addition, the administration of TCI904 alleviated mood disorders caused by a HFD. Taking the recommended human dose of TCI904 did not affect the liver or kidney function, indicating that TCI904 has sufficient in vivo safety. Taken together, the results of the present study contributed towards validation of the probiotic benefits of lactic acid starter microflora. Orally taken TCI904 exhibited positive immune- and metabolic-modulating, and anxiolytic properties, especially in HFD-induced obesity. [ABSTRACT FROM AUTHOR]

The aroma of the fermented milk produced by twenty-eight Lactobacillus delbrueckii subsp. bulgaricus strains was evaluated via quantitative descriptive analysis. According to the sensory analysis results, the fermented milks were grouped into milky-type, cheesy-type, fermented-type and miscellaneous-type. The representative samples of cheese-type and fermented-type were analyzed by headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) and flavoromics. A total of 95 volatile compounds were identified and particularly, 12 aroma-active compounds were detected by using gas chromatography-olfactometry-mass spectrometry (GC-O-MS). Among the different aroma types, 2,3-butanedione, δ-decalactone, acetaldehyde, butanoic acid, acetic acid and hexanoic acid were finally screened out as the key aroma-active compounds by quantitative and odor activity value (OAV) analysis combined with aroma recombination, omission and addition experiments. These findings were valuable in developing specific fermented milk products with different aroma profiles.

The applicability of two lactic acid bacterial strains with probiotic potential and bioprotective properties as additions in the starter culture in yogurt fermentation was examined. The studied strains, Lactobacillus delbrueckii subsp. bulgaricus KZM 2-11-3 and Lactiplantibacillus plantarum KC 5-12, inhibited the growth of Kluyveromyces lactis, Kluyveromyces marxianus, and Saccharomyces cerevisiae. The strain L. delbrueckii subsp. bulgaricus KZM 2-11-3 directly inhibited Escherichia coli. The important characteristics for the quality of the yogurt product, such as physicochemical parameters during fermentation and storage, rheological characteristics, and sensory changes during the storage of samples were determined. The yogurt samples with the strains did not differ in most parameters from the control yogurt with the commercial starter. The added strains showed stable viability in the yogurt samples during storage. The yogurt sample with L. delbrueckii subsp. bulgaricus KZM 2-11-3 and the sample with both strains based on the total evaluation were very similar to the control yogurt with the commercial starter. Using these strains as probiotic supplements to enrich the starter cultures in yogurt production will contribute to developing new products with benefits to human health.

Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus are commonly used together as a fermented milk starter. This study aimed to find the optimal ratio of two strains showing favorable fermentation characteristics, Lactobacillus delbrueckii subsp. bulgaricus T50 (T50) and Streptococcus thermophilus S10 (S10), in fermentation and explore their metabolic interaction. The optimal strain ratio was determined to be 1: 1000. The milk fermented with the optimal ratio had higher elasticity and viscosity, reached the gel point quickly, and had a strong gel structure compared to the commercial starters. T50+S10 exhibited favorable fermentation characteristics and storage stability, most similar to YF-L922, suggesting its potential to be developed as a commercial starter for fermented milk. Metabolomics analysis revealed that the T50+S10 combination enhanced the utilization of succinic acid, L-tyrosine, and L-tryptophan, promoting their mutualistic growth. T50 likely increased the availability of amino acid derivatives, small peptides, and calcium pantothenate to support S10 growth. These findings confirm the impact of L. bulgaricus and S. thermophilus ratio on fermented milk quality and provide insights into their metabolic-level interaction during fermentation. This study holds significance for the development and application of starter cultures in the dairy industry. [Display omitted] • Optimal starter ratio: 1:1000 of L. bulgaricus T50 and S. thermophilus S10. • Shortens gelation time, enhanced gel structure, and storage stability. • Enhances succinate, tyrosine, and tryptophan metabolism. • Provides amino acid derivatives and small peptides. • Facilitates pantothenate synthesis. [ABSTRACT FROM AUTHOR]

Simple Summary: Lactobacillus delbrueckii subsp. bulgaricus (LDB) is an important candidate for antibiotic replacement in pig production. In this study, LDB and antibiotic diets were fed to the LDB and antibiotic groups of female growing-finishing pigs, respectively. 16S rRNA sequencing was used to identify different microbiota. Liquid chromatography-mass spectrometry-based non-targeted metabolomics approaches were used to identify different metabolites. The co-occurrence network of the fecal microbiota and metabolite was analyzed. The results contain information on pig growth performance, microbiota data, metabolite data and co-occurrence networks, supporting the possibility of LDB as an antibiotics replacement in pig production. Lactobacillus delbrueckii subsp. bulgaricus (LDB) is an approved feed additive on the Chinese 'Approved Feed Additives' list. However, the possibility of LDB as an antibiotic replacement remains unclear. Particularly, the effect of LDB on microbiota and metabolites in the gastrointestinal tract (GIT) requires further explanation. This study aimed to identify the microbiota and metabolites present in fecal samples and investigate the relationship between the microbiota and metabolites to evaluate the potential of LDB as an antibiotic replacement in pig production. A total of 42 female growing-finishing pigs were randomly allocated into the antibiotic group (basal diet + 75 mg/kg aureomycin) and LDB (basal diet + 3.0 × 109 cfu/kg LDB) groups. Fecal samples were collected on days 0 and 30. Growth performance was recorded and assessed. 16S rRNA sequencing and liquid chromatography-mass spectrometry-based non-targeted metabolomics approaches were used to analyze the differences in microbiota and metabolites. Associations between the differences were calculated using Spearman correlations with the Benjamini–Hochberg adjustment. The LDB diet had no adverse effect on feed efficiency but slightly enhanced the average daily weight gain and average daily feed intake (p > 0.05). The diet supplemented with LDB increased Lactobacillus abundance and decreased that of Prevotellaceae_NK3B31_group spp. Dietary-supplemented LDB enhanced the concentrations of pyridoxine, tyramine, D-(+)-pyroglutamic acid, hypoxanthine, putrescine and 5-hydroxyindole-3-acetic acid and decreased the lithocholic acid concentration. The Lactobacillus networks (Lactobacillus, Peptococcus, Ruminococcaceae_UCG-004, Escherichia-Shigella, acetophenone, tyramine, putrescine, N-methylisopelletierine, N1-acetylspermine) and Prevotellaceae_NK3B31_group networks (Prevotellaceae_NK3B31_group, Treponema_2, monolaurin, penciclovir, N-(5-acetamidopentyl)acetamide, glycerol 3-phosphate) were the most important in the LDB effect on pig GIT health in our study. These findings indicate that LDB may regulate GIT function through the Lactobacillus and Prevotellaceae_NK3B31_group networks. However, our results were restrained to fecal samples of female growing-finishing pigs; gender, growth stages, breeds and other factors should be considered to comprehensively assess LDB as an antibiotic replacement in pig production. [ABSTRACT FROM AUTHOR]

The present study was designed to investigate the effects of dietary non-encapsulated and microencapsulated Lactobacillus delbrueckii subsp. bulgaricus on growth performance, intestinal enzymatic activities, antioxidant capacity and hepato-biochemical parameters of rainbow trout before or after exposure to lead via diet. Fingerling fish (16 ± 4 g) were divided into four groups: negative control (NC), positive control (PC), probiotic (PR) and encapsulated probiotic (EN-PR). During the pre-exposure period (days 0–45), fish in the NC and PC groups received the basal diet, whereas fish in the PR and EN-PR groups were fed with basal diet containing 108 CFU g−1 feed of non-encapsulated and microencapsulated probiotic, respectively. During the exposure period (days 46–66), the fish in the probiotic and PC groups were co-treated with 500 μg g−1 feed of lead nitrate. Blood, liver and gut samples were taken at days 0, 45, 52, 59 and 66. The results revealed that growth performance and intestinal enzymatic activities were significantly (P<0.05) improved in the probiotic groups compared to the NC group (day 45). Dietary exposure to lead resulted in the highest levels of liver aspartate aminotransferase (AST), liver alkaline phosphatase (ALP) and serum malondialdehyde (MDA), and the lowest activities of serum superoxide dismutase (SOD) and catalase (CAT) in the PC group (day 66). The levels of liver ALP were significantly (P<0.05) lower in the probiotic groups compared to the NC and PC groups prior to and after exposure to dietary lead. Serum levels of total protein, albumin, SOD, CAT and glutathione (GSH) were significantly increased in fish fed with both non-encapsulated and microencapsulated probiotics (P<0.05). However, microencapsulated probiotic showed the greatest potential for alleviation of the disturbed activities of intestinal and hepatic enzymes, and improvement of serum biochemical and antioxidant parameters. Our findings suggest that L. delbrueckii subsp. bulgaricus, particularly in the microencapsulated form, can be used as a potential probiotic to protect rainbow trout from dietborne lead toxicity. [ABSTRACT FROM AUTHOR]

The goal of this study was to ferment yoghurt from milk using lactic acid bacteria found in pinecones and to examine the cell viability and lipid peroxidation levels of the fermented yoghurt on Vascular Endothelial Cell Line ECV304. ECV304 was cultured in vitro. To determine cell viability, the various concentrations of yoghurt extract fermented with pinecone were given to cultured cells using the MTT Assay. At the same doses as the MTT Assay, the Lipid Peroxidation (LPO) Assay was employed to evaluate the malondialdehyde (MDA) levels of cells. Acridine orange/Ethidium Bromide staining technique was applied to detect apoptosis. Gas Chromatography-Mass Spectrometry was used to identify the volatiles in yoghurt fermented with the pinecone. All dosages of pinecone fermented yoghurt enhanced the cell viability of the human healthy vascular endothelial cell line ECV304 and decreased MDA levels, as validated by fluorescence microscopy pictures. The primary essential oils identified in yoghurt fermented with pinecone were hexadecanoic acid, eicosanoic acid, stearic acid, and 2-palmitoylglycerol. In this work, the effects of yoghurt fermented with pinecones on human healthy cell lines were examined for the first time. The study discovered that this yoghurt promotes the proliferation of healthy human cells while decreasing oxidative stress in these cells. [ABSTRACT FROM AUTHOR]

Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus) is widely used as a starter for yogurt and cheese worldwide. Despite the economic importance of this bacterium in the dairy industry, there have been few genetic studies involving knockout or overexpression mutants to identify the functions of L. bulgaricus genes. One of the main reasons for this gap is the low transformation efficiency of available L. bulgaricus chromosome-integrating vectors upon performing conventional electroporation. We previously proposed the conjugal plasmid pAMβ1 as an integration vector for L. bulgaricus, as conjugation could avert the need for a restriction modification system; pAMβ1 does not replicate and integrate into the chromosome of L. bulgaricus. Here, we describe an effective chromosomal manipulation system involving a novel shuttle vector pGMβ1, which could improve the operability of the broad host-range conjugal plasmid pAMβ1. We further developed an enhanced filter-mating method for conjugation. To validate this system, the effectiveness of conversion of the lactate dehydrogenase gene D-ldh of L. bulgaricus to the L-ldh form of Streptococcus thermophilus was examined. As pGMβ1 and pAMβ1 are unable to replicate in L. delbrueckii subsp. delbrueckii, they were chromosomally integrated. However, these plasmids could replicate in L. delbrueckii subsp. indicus and sunkii. This integration system could unearth important gene functions in L. bulgaricus and thus improve its applications in the dairy industry. Moreover, this conjugation system could be used as a stable vector for the transformation of long cluster genes in several species of lactic acid bacteria. [ABSTRACT FROM AUTHOR]

Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus) is a microaerophylic anaerobe, which is widely used in the production of yogurt, cheese, and other fermented dairy products. L. bulgaricus and its partner Streptococcus thermophilus were used as starter cultures of yogurt in the world for thousands of years. In our previous study, L. bulgaricus LDB-C1 was obtained from traditional fermented milk, and possessed some characteristics like high exopolysaccharide yield and good fermentation performance. The analysis of its CRISPR–Cas system, antibiotic resistance, virulence factors, and mobile elements, was performed to reveal the stability of the strain LDB-C1. It was found that LDB-C1 contains a plenty of spacers in the CRISPR region, indicating it might have better performance against the infection of phages and plasmids. Furthermore, the acquired or transmittable antibiotic resistance/virulence factor genes were absent in the tested L. bulgaricus strain LDB-C1. [ABSTRACT FROM AUTHOR]

Abstract Background Aerobic growth provides benefits in biomass yield and stress tolerance of Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus). Catabolite control protein A (CcpA) is a master regulator involved in the aerobic and anaerobic growth, metabolic production and stress response in L. bulgaricus, but its potential molecular mechanisms remains unclear. The aim of this study is to elucidate the role of CcpA in L. bulgaricus in aerobic growth at the proteomic perspective. Results The differential proteomic analysis was performed on the L. bulgaricus ATCC11842 and its ccpA inactivated mutant strain using iTRAQ technology. A total of 132 differentially expressed proteins were obtained, among which 58 were up-regulated and 74 were down-regulated. These proteins were mainly involved in the cellular stress response, carbohydrate and energy metabolism, amino acid transport and protein synthesis, genetic information processing. Moreover, inactivation of ccpA negatively affected the expression of key enzymes involved in glycolysis pathway, while it enhanced the expression of proteins related to the pyruvate pathway, supporting the conclusion that CcpA mediated the shift from homolactic fermentation to mixed acid fermentation in L. bulgaricus. Conclusions Overall, these results showed that the role of CcpA in L. bulgaricus as a pleiotropic regulator in aerobic metabolism and stress response. This proteomic analysis also provide new insights into the CcpA-mediated regulatory network of L. bulgaricus and potential strategies to improve the production of starter and probiotic cultures based on the metabolic engineering of global regulators.

Gene feoA plays an important role in cell growth because of its function of transport Fe2+ which is a necessary element for cells. In this study, the recombinant plasmid pUC19-feoA-Tet was successfully constructed using the inserted gene inactivation method. Using the homologous recombination technique, the tet gene was used as a resistance screening marker to knock out the feoA gene of Lactobacillus delbrueckii subsp. bulgaricus 34.5 (strain 34.5). Comparative analysis of growth curves revealed the growth changes in the absence of feoA gene in strain 34.5. The results showed that the growth of the bacteria was prolonged by 2 h and could be restored in the stationary phase. To further study whether feoA is related to the cell division of strain 34.5, the qPCR experiment was carried out. The results showed that, compared with the wild-type strain, the expression of genes related to cell division in the mutant strain was up-regulated in the pre-log phase, down-regulated in the late-log phase, and returned to the original level in the stationary phase. These findings provide ideas for Lactobacillus delbrueckii subsp. bulgaricus to control division and cell cycle. [ABSTRACT FROM AUTHOR]

The acid-producing, viscosity-increasing, and aroma-producing capacities and laboratory storage stabilities of ten strains of Lactobacillus delbrueckii subsp. bulgaricus were measured. The probiotic characteristics of the strains were also explored by monitoring their antibiotic resistance, antibacterial activities, and β-galactosidase (β-gal), α-galactosidase (α-gal), and lactate dehydrogenase (LDH) activities. Single-strain fermentation experiments show that the strain KSDB-1 had a short coagulation time (approximately 6.3 h), a lactic acid degree of 76.02ºT upon coagulation, and good acid-producing ability. The viscosity and water holding capacity (1305.67 mPa-s and 50.55%, respectively) were significantly higher than those of other strains (p<0.05). Aroma production of strains HDS-13, DDB14, and KSDB-1 was superior. Strain HDS-13 displayed a diacetyl content of 2.88 mg/L and an acetaldehyde content of up to 30.08 mg/L. These attributes could effectively improve the flavor of the yoghurt product. Probiotic tests show that all the ten tested strains were sensitive to most antibiotics and thus would be relatively safe to use. Strains HDS-13, DDB-14, HDB-1, HDS-18, and KSDB-1 could inhibit six pathogenic bacteria and effectively inhibited the growth of pathogenic intestinal bacteria. The LDH activities of strains HDS-12 and KSDB-1 were relatively high. The β-gal activities of strains HDS-12 and HDB-17 were relatively greater than that of the other strains. The α-gal activity of strain DDS-15 was significantly higher than those of other strains (p< 0.05), reaching 1.3263 U/mg. The collective data indicate that strain KSDB-1 has excellent fermentation properties and, to a certain degree, satisfactory probiotic properties. DDS-15 has potential in industrial application for yogurt fermentation. [ABSTRACT FROM AUTHOR]

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The probiotic efficacy and fermentative ability of Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus), a widely used probiotic, is majorly affected by its acid tolerance. Here, we conducted whole-genome sequencing of the high acid-tolerant L. bulgaricus LJJ stored in the laboratory. Compared with the whole genome of low acid-tolerant strain L. bulgaricus ATCC11842, the results show that 16 candidate acid-tolerant genes may be involved in the regulation of the acid tolerance of L. bulgaricus LJJ. Association analysis of candidate acid-tolerant genes and acid-tolerant traits of different L. bulgaricus strains revealed that the three genes dapA, dapH, and lysC are the main reasons for the strong acid tolerance of L. bulgaricus LJJ. The results of real-time quantitative PCR (RT-qPCR) supported this conclusion. KEGG pathway analysis showed that these three acid-tolerant genes are involved in the synthesis of lysine; the synthesis of lysine may confer L. bulgaricus LJJ strong acid tolerance. This study successfully revealed the acid tolerance mechanism of L. bulgaricus LJJ and provides a theoretical basis for the subsequent selection of strains with high acid tolerance for improved probiotic functions. Key points: • Three genes are identified as acid-tolerant genes, respectively, lysC, dapA, and dapH. • LysC and dapA are the major key genes in the synthesis of lysine. • The synthesis of lysine may confer L. bulgaricus LJJ strong acid tolerance. [ABSTRACT FROM AUTHOR]

The aim of this research was to determine the optimal medium for Exopolysaccharides (EPS) production by a Lactobacillus delbrueckii subsp. bulgaricus ropy strain isolated from a locally produced commercial fermented milk, in reconstituted skim milk (RSM) 10% (w/v), milk whey (MW), and soy milk whey (SMW), under optimal growth conditions for this strain. Milk whey was made by coagulating fresh milk using papaya latex 3% (v/v); soy milk whey was obtained from tofu household industry. The chemical composition of the substrate media was determined by proximate analysis, and sterilization was accomplished in an autoclave at 121°C for 15 min. Culture media were inoculated with 1% (v/v) of a starter culture of L. delbrueckii subsp. bulgaricus and then incubated at 30°C for 16 hr. EPS production, lactic acid content, cell counting, and pH were determined after the media were cooled at 5°C. Findings showed that on the basis of the growth characteristics of L. delbrueckii subsp. bulgaricus, the best medium for EPS production was RSM 10% (258.60 ± 26.86 mg/L) compared to the milk whey (69.60 ± 9.48 mg/L) and soy milk whey (49.80 ± 9.04 mg/L). [ABSTRACT FROM AUTHOR]

Gioddu is the sole variety of fermented milk originating in Italy. Despite the long history of consumption, Gioddu still represents an undisclosed source of microbial diversity. The present study was aimed to get an insight into the bacterial and fungal diversity of Gioddu samples collected from two artisan producers located in Sardinia. To this end 3 batches of Gioddu were collected from each producer and subjected to Polymerase Chain Reaction–Denaturing Gradient Gel Electrophoresis (PCR-DGGE) analyses. Gioddu was produced with sheep milk in accordance with the local tradition. Regarding the bacterial population, a low biodiversity emerged. In more detail, the sole species Lactobacillus delbrueckii subsp. bulgaricus was detected in all the samples, irrespective of the producer or the batch. A more ample microbial diversity was highlighted for the fungal population that included closest relatives to Pichia cactophila, Kluyveromyces marxianus and Galactomyces candidum. Based on the results, the detected bacterial and fungal species generally clustered in accordance with the producer, irrespective of the batch considered. It is noteworthy that, Gioddu revealed several microbiological similarities with kefir beverage, thus suggesting, by analogy, potential health benefits related to its consumption. More research is needed to better clarify the microbiota composition of Gioddu by using more powerful metagenomic techniques. [ABSTRACT FROM AUTHOR]

Senyawa asam laktat sangat dibutuhkan di dunia industri. Namun produksi dengan menggunakan mikrob masih menggunakan bahan pangan sebagai substratnya. Alternatif substrat untuk produksi asam laktat sebagai pengganti penggunaan bahan pangan sangat diperlukan industri. Tetes tebu merupakan salah satu substrat yang kaya akan sumber karbon yang dapat digunakan sebagai komponen media pertumbuhan bakteri. Ketersediaannya melimpah dan harganya murah. Tujuan penelitian ini adalah tetes tebu dapat digunakan sebagai alternatif sumber karbon bakteri Lactobacillus delbrueckii subsp. bulgaricus untuk menghasilkan asam laktat. Langkah penelitian ini meliputi hidrolisis dan detoksifikasi tetes tebu, uji kualitatif gula pereduksi tetes tebu, analisis gula total dengan metode fenol sulfat, penentuan kurva pertumbuhan bakteri, produksi dan ekstraksi asam laktat, serta analisis kualitatif asam laktat dengan menggunakan kromatografi cair kinerja tinggi. Hasil penelitian menunjukkan bahwa tetes tebu dapat digunakan sebagai alternatif sumber karbon. Hal ini terbukti bakteri dapat tumbuh dengan baik ketika media diberi 0.5% tetes tebu. Konsentrasi gula total tetes tebu adalah 1090 g/L. Uji gula pereduksi menunjukkan hasil yang positif untuk uji Selliwanof, uji Benedict, dan uji Barfoed. Pertumbuhan optimum L. delbrueckii subsp. bulgaricus terjadi pada suhu 42°C dengan agitasi 150 rpm. Produksi asam laktat dilakukan selama 24 jam. Kadar asam laktat yang dihasilkan sebesar 2.80% dengan biomassa sel kering sebesar 0.002 g/L dan pH media fermentasi sebesar 4.0. Hasil analisis kualitatif kromatografi cair kinerja tinggi juga menunjukkan bahwa produk dari hasil fermentasi adalah asam laktat. Abstract. Lactic acid is needed as an industrial feed. However, by using a microbial production still uses food material as a substrate. Alternative substrates for the production of lactic acid is needed in industry. Molasses are potential substrates due to the richness in carbon. Molasses also widely available and low-cost material. The objective of the research is molasses can be used as a carbon source needed by Lactobacillus delbrueckii subsp. bulgaricus to produce lactic acid. This study consisted of hydrolysis and detoxification of molasses, analysis qualitative test of reducing sugar from molasses, analysis of total sugar by phenol sulfuric acid, determination of bacterial growth, production and extraction of lactic acid, and analysis of lactic acid using high performance liquid chromatography. The results showed that molasses can be used as an alternative carbon source as indicated by growth of bacteria when the media were given 0.5% molasses. Concentration of total sugar molasses was 1090 g/L. The reducing sugar test showed positive results for the Selliwanoff, Benedict, and Barfoed tests. The optimum of L. delbrueckii subsp. bulgaricus growth was at temperature of 42° C and 150 rpm of agitation. Production of lactic acid was conducted in 24 hours. The result of lactic acid from the production was 2.80%. The dry cell biomass was 0.002 g/ L at pH of fermentation media was 4.0. Analysis HPLC also showed that lactic acid was the product of fermentation.

Lactobacillus delbrueckii subsp. bulgaricus is one of the predominant lactic acid bacterial species used as starter cultures in industrial fermented dairy manufacturing, as it strongly affects the quality of the products. Volatile flavor compound profiles and fermentation characteristics are considered to be the most important indicators for starter culture screening. In the present study, volatile compounds in milk fermented by 17 test strains of L. delbrueckii subsp. bulgaricus and a commercial strain used as a control were identified using solid-phase microextraction (SPME) methods coupled with gas chromatography mass spectrometry (GC-MS). In total, 86 volatile flavor compounds were identified in the fermented milk upon completion of fermentation, including 17 carboxylic acids, 14 aldehydes, 13 ketones, 29 alcohols, 8 esters, and 5 aromatic hydrocarbon compounds. Various volatile flavor compounds (acetaldehyde, 3-methyl-butanal, (E)-2-pentenal, hexanal, (E)-2-octenal, nonanal, 2,3-butanedione, acetoin, 2-heptanone, 2-non-anone, formic acid ethenyl ester) were identified due to their higher odor activity values (>1). In addition, of the 17 test strains of L. delbrueckii subsp. bulgaricus, IMAU20312 (B14) and IMAU62081 (B16) strains exhibited good fermentation characteristics in milk compared with the control strain. The combination of the volatile flavor compound profile and fermentation characteristics in this work could be useful when selecting lactic acid bacteria that may serve as important resources in the development of novel fermented milk products.

Background: Aerobic growth provides benefits in biomass yield and stress tolerance of Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus). Catabolite control protein A (CcpA) is a master regulator involved in the aerobic and anaerobic growth, metabolic production and stress response in L. bulgaricus, but its potential molecular mechanisms remains unclear. The aim of this study is to elucidate the role of CcpA in L. bulgaricus in aerobic growth at the proteomic perspective. Results: The differential proteomic analysis was performed on the L. bulgaricus ATCC11842 and its ccpA inactivated mutant strain using iTRAQ technology. A total of 132 differentially expressed proteins were obtained, among which 58 were up-regulated and 74 were down-regulated. These proteins were mainly involved in the cellular stress response, carbohydrate and energy metabolism, amino acid transport and protein synthesis, genetic information processing. Moreover, inactivation of ccpA negatively affected the expression of key enzymes involved in glycolysis pathway, while it enhanced the expression of proteins related to the pyruvate pathway, supporting the conclusion that CcpA mediated the shift from homolactic fermentation to mixed acid fermentation in L. bulgaricus. Conclusions: Overall, these results showed that the role of CcpA in L. bulgaricus as a pleiotropic regulator in aerobic metabolism and stress response. This proteomic analysis also provide new insights into the CcpA-mediated regulatory network of L. bulgaricus and potential strategies to improve the production of starter and probiotic cultures based on the metabolic engineering of global regulators. [ABSTRACT FROM AUTHOR]

Lactobacillus delbrueckii subsp. bulgaricus is one of the predominant lactic acid bacterial species used as starter cultures in industrial fermented dairy manufacturing, as it strongly affects the quality of the products. Volatile flavor compound profiles and fermentation characteristics are considered to be the most important indicators for starter culture screening. In the present study, volatile compounds in milk fermented by 17 test strains of L. delbrueckii subsp. bulgaricus and a commercial strain used as a control were identified using solid-phase microextraction (SPME) methods coupled with gas chromatography mass spectrometry (GC-MS). In total, 86 volatile flavor compounds were identified in the fermented milk upon completion of fermentation, including 17 carboxylic acids, 14 aldehydes, 13 ketones, 29 alcohols, 8 esters, and 5 aromatic hydrocarbon compounds. Various volatile flavor compounds (acetaldehyde, 3-methyl-butanal, (E)-2-pentenal, hexanal, (E)-2-octenal, nonanal, 2,3-butanedione, acetoin, 2-heptanone, 2-non-anone, formic acid ethenyl ester) were identified due to their higher odor activity values (>1). In addition, of the 17 test strains of L. delbrueck ii subsp. bulgaricus , IMAU20312 (B14) and IMAU62081 (B16) strains exhibited good fermentation characteristics in milk compared with the control strain. The combination of the volatile flavor compound profile and fermentation characteristics in this work could be useful when selecting lactic acid bacteria that may serve as important resources in the development of novel fermented milk products. [ABSTRACT FROM AUTHOR]

Summary: Lactobacillus delbrueckii subsp. bulgaricus CH9‐3 proteinase is an enzyme that plays an important role in yogurt fermentation, by which its use is linked to gel properties of yogurt. In this work, a modified glucono‐δ‐lactone (GDL) acidification model was used to simulate the fermentation of yogurt and study the effect of CH9‐3 proteinase on GDL‐acidified milk gel. The results showed that the proteinase significantly improved the quality of milk gel by increasing its firmness, consistency, and viscosity index, while decreasing its syneresis. Furthermore, the proteinase could accelerate the formation of milk gel as indicated by the decrease in surface charge of milk gel. The findings demonstrate that CH9‐3 proteinase has a positive effect on the properties of milk gel, and thus may have promising applications in the yogurt making industry. [ABSTRACT FROM AUTHOR]

The proteinase-encoding prtB gene of Lactobacillus (Lb.) delbrueckii (d.) subsp. bulgaricus 92059 was cloned and sequenced. Two soluble, secreted, C-terminally His-tagged derivatives were constructed and expressed in Lactococcus lactis by means of the NICE® Expression System. In both obtained derivatives PrtBb and PrtB2, the C-terminal, cell wall-binding domain was deleted. In addition, in derivative PrtB2, the C-terminal part of the B domain was deleted and the signal sequence was replaced by a lactococcal export signal. The affinity-purified derivatives were both proteolytically active. Peptide hydrolysates produced from casein with each of the derivatives showed identical peptide composition, as determined by liquid chromatography–mass spectrometry. Comparison of the peptides generated to those generated with living Lb. d. subsp. bulgaricus 92059 cells (Kliche et al. Appl Microbiol Biotechnol 101:7621–7633, 2017) showed that β-casein was the casein fraction most susceptible to hydrolysis and that some significant differences were observed between the products obtained by either the derivatives or living Lb. d. subsp. bulgaricus 92059 cells. When tested for biological activity, the hydrolysate obtained with PrtBb showed 50% inhibition of angiotensin-converting enzyme at a concentration of 0.5 mg/ml and immunomodulation/anti-inflammation in an in vitro assay of TNF-α induced NFκB activation at concentrations of 5 and 2.5 mg/ml, respectively. The enzymatically obtained hydrolysate did not show any pro-inflammatory or cytotoxic activity. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the proliferation effect of fractionated lotus seed resistant starch (LRS3-20%, LRS3-30%) and the structural changes following fermentation. Fractionated lotus seed resistant starch, especially LRS3-20%, promoted the proliferation of these probiotics, and Bifidobacterium longum produced large quantities of acetic acid, while Lactobacillus delbrueckii subsp. bulgaricus produced lactic acid. Additionally, the probiotics with lotus seed resistant starch (LRS3) and LRS3-20% survived more successfully in simulated gastrointestinal solutions compared to glucose, LRS3-30% and high amylose maize starch, but LRS3 and LRS3-20% differed in their abilities to enhance the tolerance to acidic buffer, bile acid and simulated gastric juice. Furthermore, after fermentation, fractionated lotus seed resistant starch displayed a loose, rough surface. The crystalline and double helical structure increased as the amount of amorphous and sub-crystalline structure reduced following fermentation. Interestingly, structural changes were correlated with the original structures and utilisation by the probiotics. [ABSTRACT FROM AUTHOR]

Lactobacillus delbrueckii subsp. bulgaricus is currently one of the most valuable lactic acid bacteria (LAB) and widely used in global dairy industry. The acid tolerance and adaptation ability of LAB is the key point of their survival and proliferation during fermentation process and in gastrointestinal tract of human body. Two component system (TCS) is one of the most important mechanisms to allow bacteria to sense and respond to changes of environmental conditions. TCS typically consists of a histidine protein kinase (HPK) and a corresponding response regulator (RR). Our previous study indicated a TCS (JN675228/JN675229) was involved in acid adaptation in L. bulgaricus. To reveal the role of JN675228 (HPK1)/JN675229 (RR1) in acid adaptation, the target genes of JN675228 (HPK1)/JN675229 (RR1) were identified by means of a proteomic approach complemented with transcription data in the present study. The results indicated that HPK1/RR1 regulated the acid adaptation ability of bacteria by means of many pathways, including the proton pump related protein, classical stress shock proteins, carbohydrate metabolism, nucleotide biosynthesis, DNA repair, transcription and translation, peptide transport and degradation, and cell wall biosynthesis, etc. To our knowledge, this is the first report with the effect of acid adaptation-related TCS HPK1/RR1 on its target genes. This study will offer experimental basis for clarifying the acid adaptation regulation mechanism of L. bulgaricus, and provide a theoretical basis for this bacterium in industry application. [ABSTRACT FROM AUTHOR]

The aim of the study was to investigate the usability of wheat straw in the production of L-lactic acid via fermentation applying by newly isolated lactic acid bacteria (LAB) strains belonging to the genus Lactobacillus and its combinations. Biotreatment of wheat straw was carried out through a three-step procedure consisting of: (i) physical pre-treatment, (ii) enzymatic hydrolysis and (iii) fermentation with LAB strains under laboratory conditions. Lactic acid production, residual sugar, cell biomass, pH medium and the influence of ions such as magnesium, calcium and sodium on efficiency of enzymatic hydrolysis of wheat straw were the main features examined. Moreover, optimal parameters for enzymatic hydrolysis were selected. Increased lactic acid production was observed, when mixed LAB cultures were used in comparison to individual ones. The results confirmed that tested wheat straw could be used for lactic acid and L-lactic acid production using selected enzymes and combined LAB strains. [ABSTRACT FROM AUTHOR]

Background. The efficacy of Lactobacillus delbrueckii subsp. bulgaricus as starter cultures for the dairy industry depends largely on the number of viable and active cells. Freeze-drying is the most convenient and successful method to preserve the bacterial cells. However, not all strains survived during freeze-drying. Methods. The effects of six substances including NaCl, sorbitol, mannitol, mannose, sodium glutamate, betaine added to the MRS medium on the growth and freeze-drying survival rate and viable counts of Lb. delbrueckii subsp. bulgaricus were studied through a single-factor test and Plackett-Burman design. Subsequently, the optimum freeze-drying conditions of Lb. delbrueckii subsp. bulgaricus were determined. Results. Lb. delbrueckii subsp. bulgaricus survival rates were up to the maximum of 42.7%, 45.4%, 23.6%, while the concentrations of NaCl, sorbitol, sodium glutamate were 0.6%, 0.15%, 0.09%, respectively. In the optimum concentration, the viable counts in broth is 6.1, 6.9, 5.13 (×108 CFU/mL), respectively; the viable counts in freeze-drying power are 3.09, 5.2, 2.7 (×1010 CFU/g), respectively. Conclusion. Three antifreeze factors including NaCl, sorbitol, sodium glutamate have a positive effect on the growth and freeze-drying of Lb. delbrueckii subsp. bulgaricus. The results are beneficial for developing Lb. delbrueckii subsp. bulgaricus. [ABSTRACT FROM AUTHOR]

Lead (Pb) is a toxic contaminating heavy metal that can cause a variety of hazardous effects to both humans and animals. In the present study, Lactobacillus delbrueckii subsp. bulgaricus KLDS1.0207 (L. bulgaricus KLDS1.0207), which has a remarkable Pb binding capacity and Pb tolerance, was selected for further study. It was observed that the thermodynamic and kinetic model of L. bulgaricus KLDS1.0207 Pb binding respectively fit with the Langmuir-Freundlich model and the pseudo second-order kinetic model. Scanning electron microscopy and energy dispersive spectroscopy analysis disclosed that the cell surfaces were covered with Pb and that carbon and oxygen elements were chiefly involved in Pb binding. Combined with Fourier transform infrared spectroscopy analysis, it was revealed that the carboxyl, phosphoryl, hydroxyl, amino and amide groups were the main functional groups involved in the Pb adsorption. The protective effects of L. bulgaricus KLDS1.0207 against acute Pb toxicity in mice was evaluated by prevention and therapy groups, the results in vivo showed that L. bulgaricus KLDS1.0207 treatment could reduce mortality rates, effectively increase Pb levels in the feces, alleviate tissue Pb enrichment, improve the antioxidant index in the liver and kidney, and relieve renal pathological damage. Our findings show that L. bulgaricus KLDS1.0207 can be used as a potential probiotic against acute Pb toxicity. [ABSTRACT FROM AUTHOR]

The rheological and physical characteristics of non-fat set yogurt produced using co-cultures of ropy EPS-producingStreptococcus thermophilusS3.3 andLactobacillus delbrueckiisubsp.bulgaricusLTM and ofStreptococcus thermophilusS3.3 andLactobacillus delbrueckiisubsp.bulgaricusH+-ATPase-defective mutant L6 under different conditions were studied. Yogurts produced with mutant L6 had a higher pH and water-holding capacity and better textural properties compared to those produced with the LTM strain. The highest storage modulus (G′) and thixotropic loops were found for yogurt made with L6 at 42°C on day 21 of cold storage. This yogurt contained a network of thick, continuous protein aggregates and large void spaces. [ABSTRACT FROM AUTHOR]