RESUMO
Lactic acid bacteria are probiotics in the intestines and have been widely used as natural antioxidants in the food industry. In this study, Enterococcus italicus FM5 with strong antioxidant ability was isolated from fresh milk. The safety evaluation showed that E. italicus FM5 was sensitive to ampicillin, chloramphenicol, erythromycin, vancomycin, rifampicin, and tetracycline, and was not hemolytic. Meanwhile, the whole genome information and biofunctional attributes of this strain were determined and analyzed. Subsequently, E. italicus FM5 was co-cultured with traditional yogurt starters (Streptococcus thermophilus and Lactobacillus bulgaricus) to make fermented milk. The results showed that the addition of E. italicus FM5 could improve the oxygen free radical scavenging ability of the fermented milk, and the scavenging rates of DPPH, ABTS, OH-, and O2- radicals reaching up to 95.54 %, 88.35 %, 93.65 %, and 60.29 %, respectively. Furthermore, the addition of E. italicus FM5 reduced the curd time and improved the water holding capacity of the fermented milk. Besides, the growth of Lb. bulgaricus was significantly promoted when co-cultured with E. italicus FM5, thus the survival cells were increased compared with the traditional fermentation processes. Therefore, this study emphasized the potential to manufacture fermented milk by the co-cultivation of E. italicus with traditional yogurt starters.
Assuntos
Antioxidantes , Enterococcus , Fermentação , Leite , Enterococcus/metabolismo , Enterococcus/crescimento & desenvolvimento , Animais , Leite/microbiologia , Antioxidantes/farmacologia , Probióticos , Iogurte/microbiologia , Produtos Fermentados do Leite/microbiologia , Microbiologia de Alimentos , Armazenamento de Alimentos , Streptococcus thermophilus/metabolismo , Streptococcus thermophilus/crescimento & desenvolvimento , Técnicas de Cocultura , Lactobacillus delbrueckii/metabolismo , Lactobacillus delbrueckii/crescimento & desenvolvimento , Antibacterianos/farmacologiaRESUMO
2'-Fucosyllactose (2'-FL) is postulated to provide health benefits and promote the growth of probiotics. This work was undertaken to study the effects of 2'-FL on the viability of starter cultures and Bifidobacterium strains of human origin in yogurt during refrigerated storage. Yogurts were produced containing 2'-FL (0 or 2 g/L) and Bifidobacterium strains of human origin (Bifidobacterium longum subsp. longum BB536 or Bifidobacterium longum subsp. infantis ATCC 15697) at a concentration of at least 109 CFU/mL. All yogurts were stored at 4°C for 5 weeks. Results showed that 2'-FL was stable in yogurts for at least 5 weeks of cold storage, and the addition of 2'-FL did not significantly alter yogurt fermentation parameters, associated metabolites, and the viability of mixed yogurt starter cultures and Bifidobacterium strains (p > 0.05). The addition of bifidobacteria had a negative impact (p < 0.05) on the survival rate of starter cultures, Streptococcus thermophilus and Lactobacillus delbureckii subsp. bulgaricus. Meanwhile, it is difficult to maintain a high survival rate of bifidobacteria in final yogurt products, and the addition of 2'-FL could not enhance the viability of bifidobacteria. B. longum BB536 survived at a level higher than 106 CFU/g for 28 days, while B. infantis ATCC15697 maintained this level for only 7 days. In summary, this study has shown the impact of 2'-FL and bifidobacterial species on yogurt properties, and results suggest that it is promising to use 2'-FL in yogurt products as a prebiotic. PRACTICAL APPLICATION: Yogurt is known for its beneficial effects on human health and nutrition. This study reported the production of symbiotic yogurt containing bifidobacteria and 2'-fucosyllactose (2'-FL) as a functional food for specified health uses. The viability of yogurt starter cultures and probiotic bifidobacterial strains was analyzed in this study. Moreover, this research demonstrated that 2'-FL could be added to yogurt without affecting the characteristics of yogurt significantly.
Assuntos
Bifidobacterium , Fermentação , Armazenamento de Alimentos , Probióticos , Trissacarídeos , Iogurte , Iogurte/microbiologia , Trissacarídeos/farmacologia , Bifidobacterium/crescimento & desenvolvimento , Humanos , Armazenamento de Alimentos/métodos , Refrigeração , Streptococcus thermophilus/crescimento & desenvolvimento , Viabilidade Microbiana , Microbiologia de Alimentos , Contagem de Colônia MicrobianaRESUMO
Enumeration and isolation of Streptococcus salivarius subsp. thermophilus from cheese is challenging, due to the relatively high number of species it may host. We describe medium SPY9.3 for the cultivation of S. salivarius subsp. thermophilus from cheese. The medium and related incubation conditions (SPY) was compared with 2 other protocols, M17 and ST: sensitivity was assessed by parallel cultivation of 55 strains of S. salivarius subsp. thermophilus, and selectivity by (i) parallel cultivation of 60 strains belonging to 20 different non-target species and sub-species and (ii) isolating bacteria from 3 raw-milk cheeses. Colony counts were similar on SPY9.3 and M17 (mean difference 0.07 log(cfu/mL), p > 0.001) and significantly higher on ST than on M17 and SPY9.3 (mean differences 0.42 and 0.48 log(cfu/mL), respectively, p < 0.001). SPY was more specific than ST and M17, with respectively 20%, 40%, and 50% of the investigated non-target species able to grow. S. salivarius subsp. thermophilus, Enterococcus spp., and Staphylococcus aureus were indistinguishable using all 3 protocols. Only SPY avoided growth of Lactobacillus delbrueckii subsp. lactis. Finally, ST and SPY displayed higher recoveries of S. salivarius subsp. thermophilus colonies from cheese than M17 (5.6, 5.5, and 3.0 adjusted log(cfu/mL), respectively) and the lowest proportion of non-specific isolates. The protocol described here and based on SPY9.3 presents a promising alternative to existing protocols for the enumeration and isolation of S salivarius subsp. thermophilus from cheese or other complex fermented products.
Assuntos
Queijo/microbiologia , Meios de Cultura/metabolismo , Microbiologia de Alimentos/métodos , Streptococcus thermophilus/crescimento & desenvolvimento , Streptococcus thermophilus/metabolismo , Animais , Bovinos , Contagem de Colônia Microbiana , Meios de Cultura/química , Microbiologia de Alimentos/instrumentação , Leite/microbiologia , Streptococcus thermophilus/genéticaRESUMO
Lactic acid bacteria fermentation is a safe and green technology that can modify the function of food ingredients (including proteins). In this article, egg yolks were subjected to fermentation with commercial lactic acid bacteria for 0, 3, 6 and 9 h, respectively. After fermentation treatment, the microbial composition has changed obviously (Streptococcus thermophilus increased significantly). The free sulfhydryl group (SH) contents and surface hydrophobicity of egg yolk proteins were significantly reduced. The rheological results indicated that the treated egg yolks possessed a decreased apparent viscosity. Correspondingly, the emulsifying activity of egg yolk was enhanced from 9.07 to 19.55, 23.40 and 24.61 m2/g for 3, 6 and 9 h of fermentation, respectively. And the emulsifying stability reached the maximum after 3 h of fermentation. This study investigated the relationship between structure and properties of yolk proteins, and showed that lactic acid fermentation endued egg yolk with better emulsifying properties.
Assuntos
Proteínas do Ovo/química , Gema de Ovo/química , Gema de Ovo/microbiologia , Lactobacillales/metabolismo , Animais , Proteínas do Ovo/análise , Proteínas do Ovo/metabolismo , Emulsões/química , Fermentação , Microbiologia de Alimentos , Interações Hidrofóbicas e Hidrofílicas , Reologia , Streptococcus thermophilus/crescimento & desenvolvimento , Streptococcus thermophilus/metabolismo , Compostos de Sulfidrila/química , ViscosidadeRESUMO
Camel milk, similar to cow milk, contains all of the essential nutrients as well as potentially health-beneficial compounds with anticarcinogenic, antihypertensive, and antioxidant properties. Camel milk has been used for the treatment of allergies to cow milk, diabetes, and autism. Camel milk helps decrease cholesterol levels in blood and improves metabolism. One of the most desirable food tastes is sweetness. However, the excessive ingestion of sugar negatively affects human health. Monk fruit sweetener is a natural, 0-calorie sweetener with many health-beneficial functions. Monk fruit sweetener helps decrease symptoms of asthma and diabetes, prevents oxidation and cancer, protects the liver, regulates immune function, and lowers glucose levels. Monk fruit sweetener is 100 to 250 times sweeter than sucrose. The objective of this study was to examine the influence of different concentrations of monk fruit sweetener on the physicochemical properties and microbiological counts of drinking yogurt made from camel milk. Camel milk drinking yogurt was produced with 0, 0.42, 1.27, and 2.54 g/L of monk fruit sweetener and stored for 42 d. The physicochemical characteristics and microbiological counts of yogurts were measured at d 1, 7, 14, 21, 28, 35, and 42. For the physicochemical characteristics, pH, titratable acidity, viscosity, and color [lightness-darkness (L*), red-green axis (a*), yellow-blue axis (b*), chroma (C*), and hue angle (h*)] values were evaluated. The counts of Streptococcus thermophilus, Lactobacillus bulgaricus, Lactobacillus acidophilus, coliforms, and yeast and mold were determined. Three replications were conducted. The sweetener addition significantly influenced pH, viscosity, and color (a*, b*, C*, and h*) values. Control samples had significantly higher pH values, lower viscosity, lower b* and C* values, and higher h* values than the samples with 1.27 and 2.54 g/L of monk fruit sweetener. Growth of S. thermophilus, L. bulgaricus, and probiotic culture L. acidophilus was not affected by the incorporation of monk fruit sweetener. Monk fruit sweetener can be added in camel milk yogurts as a health-beneficial 0-calorie sweetener.
Assuntos
Lactobacillus acidophilus/crescimento & desenvolvimento , Lactobacillus delbrueckii/crescimento & desenvolvimento , Leite/química , Probióticos , Streptococcus thermophilus/crescimento & desenvolvimento , Edulcorantes/química , Iogurte/microbiologia , Animais , Antioxidantes/análise , Camelus , Fenômenos Químicos , Feminino , Fermentação , Frutas/química , Iogurte/análiseRESUMO
This study investigated the bioconversion and bioaccessibility of soy isoflavones produced in sogurt fermented with S. thermophilus and L. bulgaricus during in vitro digestion. The highest survivability of S. thermophilus (6.49 log cfu/mL) and L. bulgaricus (6.48 log cfu/mL) was in oral phase. In gastric phase, the total aglycones of sogurt (26.73 g/L) increased up to 20 times than control (1.21 g/L), with a significant increase in daidzein (17.05 g/L) and genistein (9.68 g/L). Addition of 8U of ß-glucosidase into soymilk significantly increased the conversion of isoflavone in ENTII (daidzein: 0.46 g/L; genistein: 0.18 g/L) than in ENTI (daidzein: 0.33 g/L; genistein: 0.20 g/L). The particle size analysis and confocal micrographs of digesta also suggest the size of fat and protein in gastric phase to be smaller than in intestinal phase. The results indicate the prospective to develop soy-based fermented products capable of releasing high isoflavone in the digestive system.
Assuntos
Isoflavonas/metabolismo , Iogurte/análise , Cromatografia Líquida de Alta Pressão , Cromatografia de Fase Reversa , Digestão , Genisteína/metabolismo , Isoflavonas/análise , Lactobacillus delbrueckii/crescimento & desenvolvimento , Lactobacillus delbrueckii/metabolismo , Leite de Soja/metabolismo , Streptococcus thermophilus/crescimento & desenvolvimento , Streptococcus thermophilus/metabolismo , beta-Glucosidase/metabolismoRESUMO
Societal demand for plant-based foods is increasing. In this context, soya products fermented using lactic acid bacteria (LAB) are appealing because of their potential health and nutritional benefits. The thermophilic LAB Streptococcus thermophilus is an essential starter species in the dairy industry. However, while its physiology is well characterized, little is known about its general metabolic activity or its techno-functional properties when it is grown in soya milk. In this study, S. thermophilus LMD-9 growth, sugar production, and lactic acid production in soya milk versus cow's milk were measured. Additionally, the main metabolic pathways used by the bacterium when growing in soya milk were characterized using a proteomic approach. Streptococcus thermophilus LMD-9 growth decreased soya milk pH, from 7.5 to 4.9, in 5 h. During fermentation, acidification thus occurred in tandem with lactate production and increasing population size (final population: 1.0 × 109 CFU/ml). As growth proceeded, sucrose was consumed, and fructose was produced. The proteomic analysis (LC-MS/MS) of the strain's cytosolic and cell envelope-associated proteins revealed that proteins related to amino acid transport and nitrogen metabolism were the most common among the 328 proteins identified (63/328 = 19.2% of total proteins). The cell-wall protease PrtS was present, and an LMD-9 deletion mutant was constructed by interrupting the prtS gene (STER_RS04165 locus). Acidification levels, growth levels, and final population size were lower in the soya milk cultures when the ΔprtS strain versus the wild-type (wt) strain was used. The SDS-PAGE profile of the soluble proteins in the supernatant indicated that soya milk proteins were less hydrolyzed by the ΔprtS strain than by the wt strain. It was discovered that S. thermophilus can grow in soya milk by consuming sucrose, can hydrolyze soya proteins, and can produce acidification levels comparable to those in cow's milk. This study comprehensively examined the proteomics of S. thermophilus grown in soya milk and demonstrated that the cell-wall protease PrtS is involved in the LAB's growth in soya milk and in the proteolysis of soya proteins, which are two novel findings. These results clarify how S. thermophilus adapts to soya milk and can help inform efforts to develop new fermented plant-based foods with better-characterized biochemical and microbiological traits.
Assuntos
Proteínas de Bactérias/metabolismo , Serina Endopeptidases/metabolismo , Leite de Soja/metabolismo , Streptococcus thermophilus/crescimento & desenvolvimento , Streptococcus thermophilus/metabolismo , Animais , Fermentação , Ácido Láctico/análise , Ácido Láctico/metabolismo , Redes e Vias Metabólicas , Leite/química , Leite/metabolismo , Leite/microbiologia , Proteínas do Leite/metabolismo , Nitrogênio/metabolismo , Proteômica , Leite de Soja/química , Proteínas de Soja/metabolismo , Streptococcus thermophilus/enzimologia , Sacarose/metabolismo , Açúcares/análise , Açúcares/metabolismoRESUMO
In streptococci, intracellular quorum sensing pathways are based on quorum-sensing systems that are responsible for peptide secretion, maturation, and reimport. These peptides then interact with Rgg or ComR transcriptional regulators in the Rap, Rgg, NprR, PlcR, and PrgX (RRNPP) family, whose members are found in Gram-positive bacteria. Short hydrophobic peptides (SHP) interact with Rgg whereas ComS peptides interact with ComR regulators. To date, in Streptococcus thermophilus, peptide secretion, maturation, and extracellular fate have received little attention, even though this species has several (at least five) genes encoding Rgg regulators and one encoding a ComR regulator. We studied pheromone export in this species, focusing our attention on PptAB, which is an exporter of signaling peptides previously identified in Enterococcus faecalis, pathogenic streptococci and Staphylococcus aureus. In the S. thermophilus strain LMD-9, we showed that PptAB controlled three regulation systems, two SHP/Rgg systems (SHP/Rgg1358 and SHP/Rgg1299), and the ComS/ComR system, while using transcriptional fusions and that PptAB helped to produce and export at least three different mature SHPs (SHP1358, SHP1299, and SHP279) peptides while using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Using a deep sequencing approach (RNAseq), we showed that the exporter PptAB, the membrane protease Eep, and the oligopeptide importer Ami controlled the transcription of the genes that were located downstream from the five non-truncated rgg genes as well as few distal genes. This led us to propose that the five non-truncated shp/rgg loci were functional. Only three shp genes were expressed in our experimental condition. Thus, this transcriptome analysis also highlighted the complex interconnected network that exists between SHP/Rgg systems, where a few homologous signaling peptides likely interact with different regulators.
Assuntos
Transportadores de Cassetes de Ligação de ATP/metabolismo , Proteínas de Bactérias/metabolismo , Fragmentos de Peptídeos/metabolismo , Proteoma/análise , Percepção de Quorum , Streptococcus thermophilus/metabolismo , Transcriptoma , Transportadores de Cassetes de Ligação de ATP/genética , Proteínas de Bactérias/genética , Cromatografia Líquida , Regulação Bacteriana da Expressão Gênica , Streptococcus thermophilus/genética , Streptococcus thermophilus/crescimento & desenvolvimento , Espectrometria de Massas em TandemRESUMO
A plain symbiotic almond yogurt-like product was formulated and developed using a plant-based starter YF-L02 (Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus supplemented with Lactobacillus acidophilus, Lactobacillus paracasei, and Bifidobacterium animalis) and inulin; 0.6% polymerized whey protein (PWP), 0.3% pectin, and 0.05% xanthan gum were optimized for the formula of the almond yogurt alternative. Two groups with/without calcium citrate and vitamin D2 were prepared and analyzed for chemical composition, changes in pH, viscosity, and probiotic survivability during storage at 4 °C for 10 weeks. The results showed that (1) over 10 weeks storage, the differences in the pH, viscosity, and probiotic survivability between the control and the fortified samples were not significant (P > 0.05); (2) the pH of both yogurt samples decreased 0.2 units while their viscosity slightly increased during storage; (3) the populations of L. paracasei and B. animalis remained above 106 cfu/g during the storage, whereas the population of L. acidophilus decreased dramatically during the first 4 weeks, especially the control group; (4) the microstructure was examined by scanning electron microscopy, revealing a compact and denser gel structure formed by 0.6% PWP with the presence of 0.3% pectin and 0.05% xanthan gum. In conclusion, PWP might be a proper gelation agent for the formulation of symbiotic almond yogurt alternative. PRACTICAL APPLICATION: In this study, polymerized whey protein was used as a gelation agent to formulate symbiotic almond yogurt alternatives with comparable physical texture and probiotic survivability to dairy yogurt during storage. This technology may be used for the development of plant-based fermented foods.
Assuntos
Lactobacillus acidophilus/crescimento & desenvolvimento , Lactobacillus delbrueckii/crescimento & desenvolvimento , Probióticos/química , Prunus dulcis/química , Streptococcus thermophilus/crescimento & desenvolvimento , Proteínas do Soro do Leite/química , Iogurte/análise , Fermentação , Géis/química , Géis/metabolismo , Inulina/química , Inulina/metabolismo , Lactobacillus acidophilus/metabolismo , Lactobacillus delbrueckii/metabolismo , Viabilidade Microbiana , Pectinas/química , Pectinas/metabolismo , Polimerização , Prunus dulcis/metabolismo , Prunus dulcis/microbiologia , Streptococcus thermophilus/metabolismo , Viscosidade , Proteínas do Soro do Leite/metabolismo , Iogurte/microbiologiaRESUMO
ß-galactosidases, commonly referred to as lactases, are used for producing lactose-free dairy products. Lactases are usually purified from microbial sources, which is a costly process. Here, we explored the potential that lies in using whole cells of a food-grade dairy lactic acid bacterium, Streptococcus thermophilus, as a substitute for purified lactase. We found that S. thermophilus cells, when treated with the antimicrobial peptide nisin, were able to hydrolyze lactose efficiently. The rate of hydrolysis increased with temperature; however, above 50 °C, stability was compromised. Different S. thermophilus strains were tested, and the best candidate was able to hydrolyze 80% of the lactose in a 50 g/L solution in 4 h at 50 °C, using only 0.1 g/L cells (dry weight basis). We demonstrated that it was possible to grow the cell catalyst on dairy waste, and furthermore, that a cell-free supernatant of a culture of a nisin-producing Lactococcus lactis strain could be used instead of purified nisin, which reduced cost of use significantly. Finally, we tested the cell catalysts in milk, where lactose also was efficiently hydrolyzed. The method presented is natural and low-cost, and allows for production of clean-label and lactose-free dairy products without using commercial enzymes from recombinant microorganisms. KEY POINTS: ⢠Nisin-permeabilized Streptococcus thermophilus cells can hydrolyze lactose efficiently. ⢠A low-cost and more sustainable alternative to purified lactase enzymes. ⢠Reduction of overall sugar content. ⢠Clean-label production of lactose-free dairy products.
Assuntos
Lactase/metabolismo , Lactobacillales/metabolismo , Animais , Permeabilidade da Membrana Celular/efeitos dos fármacos , Meios de Cultura , Hidrólise , Lactobacillales/crescimento & desenvolvimento , Lactococcus lactis/crescimento & desenvolvimento , Lactococcus lactis/metabolismo , Lactose/análise , Lactose/metabolismo , Leite/química , Leite/microbiologia , Nisina/metabolismo , Nisina/farmacologia , Streptococcus thermophilus/efeitos dos fármacos , Streptococcus thermophilus/crescimento & desenvolvimento , Streptococcus thermophilus/metabolismo , TemperaturaRESUMO
In this study, we modified reinforced clostridial medium (RCM) to selectively enumerate and isolate Lactobacillus delbrueckii ssp. bulgaricus, a probiotic and important starter culture in the dairy industry. The disparity in the reported carbohydrate fermentation pattern of L. delbrueckii ssp. bulgaricus was used to develop a growth medium not only selective for L. delbrueckii ssp. bulgaricus but significantly inhibitory to the growth of other lactic acid bacteria. A recently modified RCM (mRCM) was optimized for this study by the addition of 0.5% fructose, 0.5% dextrose, 1% maltose, and 0.25% sodium pyruvate while replacing lactose as a carbohydrate source. The cell recovery and bacterial counts of L. delbrueckii ssp. bulgaricus in tested products (pure L. delbrueckii ssp. bulgaricus strains, starter culture, probiotic supplements, and yogurt) using our mRCM with sodium pyruvate (mRCM-PYR) were significantly higher than in the recently modified RCM and the common de Man, Rogosa, and Sharpe (MRS) culture medium. The growth of other lactic acid bacteria (Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus rhamnosus, and Lactobacillus reuteri) and Bifidobacteria was retarded in this modified medium compared with their growth in MRS and mRCM. This result is a significant improvement in the enumeration and differentiation of L. delbrueckii ssp. bulgaricus in mRCM-PYR compared with the results in MRS and mRCM where the high background growth of similar species interferes with the accuracy of bacterial population counts. Our results thus suggest that mRCM-PYR could be recommended as a reliable alternative growth medium for the selective enumeration and isolation of L. delbrueckii ssp. bulgaricus in a mixed culture.
Assuntos
Clostridium , Meios de Cultura , Lactobacillus delbrueckii/isolamento & purificação , Animais , Bifidobacterium/crescimento & desenvolvimento , Fermentação , Lactobacillales/crescimento & desenvolvimento , Lactobacillus acidophilus/crescimento & desenvolvimento , Lactobacillus delbrueckii/crescimento & desenvolvimento , Limosilactobacillus reuteri/crescimento & desenvolvimento , Lacticaseibacillus rhamnosus/crescimento & desenvolvimento , Probióticos , Streptococcus thermophilus/crescimento & desenvolvimento , IogurteRESUMO
BACKGROUND: This study aimed to evaluate the protective effect of different biopolymer systems on the viability of two probiotics (Lactobacillus rhamnosus and Streptococcus thermophilus) during storage and in vitro digestion. Methylcellulose (MC), sodium alginate (SA), and whey protein (WP)-based structures were designed and characterized in terms of pH, rheological properties, and visual appearance. RESULTS: The results highlighted that the WP-system ensured probiotic protection during both storage and in vitro digestion. This result was attributed to a combined effect of the physical barrier offered by the protein gel network and whey proteins as a nutrient for microbes. On the other hand, surprisingly, the viscous methylcellulose-based system was able to guarantee good microbial viability during storage. However, this was not confirmed during in vitro digestion. The opposite results were obtained for sodium alginate beads. CONCLUSION: The results suggest that the capacity of a polymeric structure to protect probiotic bacteria is a combination of structural organization and system formulation. © 2020 Society of Chemical Industry.
Assuntos
Biopolímeros/química , Lacticaseibacillus rhamnosus/crescimento & desenvolvimento , Probióticos/química , Streptococcus thermophilus/crescimento & desenvolvimento , Alginatos/química , Digestão , Lacticaseibacillus rhamnosus/química , Viabilidade Microbiana , Modelos Biológicos , Streptococcus thermophilus/química , Proteínas do Soro do LeiteRESUMO
In the dairy industry, exopolysaccharides (EPS) produced in situ from lactic acid bacteria are of great interest because of their contribution to product texture. Some EPS cause ropiness which might be linked to specific physical and chemical EPS properties. EPS show a broad variety of chemical structures and, because analysis is rather complex, it is still a major challenge to establish structure-function relationships. The aim of this study was to produce EPS with different degree of ropiness, perform in-depth structural elucidations and relate this information to their behaviour in aqueous solutions. After cultivation of Streptococcus thermophilus DGCC7919 and Lactococcus lactis LL-2A and subsequent EPS isolation, both EPS showed similar macromolecular properties, but pronounced differences in monosaccharide composition and glycosidic linkages. Our data suggests that mainly the side chains in the EPS from LL-2A might be responsible for a higher ropiness than that observed for EPS from DGCC7919.
Assuntos
Polissacarídeos Bacterianos/química , Reatores Biológicos , Sequência de Carboidratos , Fermentação , Glucose/metabolismo , Lactococcus lactis/química , Lactococcus lactis/crescimento & desenvolvimento , Lactococcus lactis/metabolismo , Lactose/metabolismo , Polissacarídeos Bacterianos/biossíntese , Streptococcus thermophilus/química , Streptococcus thermophilus/crescimento & desenvolvimento , Streptococcus thermophilus/metabolismoRESUMO
Thermophilic and mesophilic lactic acid bacteria (LAB), such as Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus helveticus, and Lactococcus lactis, play a crucial role in the technological and sensory quality of Mozzarella cheese. In this study, the safety (genes encoding virulence factors and antibiotic resistance) and acidifying activity of autochthonous S. thermophilus cultures were evaluated in order to choose the most suitable strain for industrial application. The safe and good acidifying culture was tested in two buffalo Mozzarella cheese batches: Mozzarella cheeses produced with autochthonous culture (SJRP107) and commercial culture (STM5). The cultivable LAB was evaluated by culture-dependent method (plate counting) and the quantification of S. thermophilus cultures (commercial and autochthonous) were evaluated by culture-independent method RealT-qPCR (real-time quantitative polymerase chain reaction). The texture, physicochemical and proteolytic properties of the Mozzarella cheeses were similar for both batches. The nonstarter LAB count was higher during manufacture than in the storage, and the RealT-qPCR indicated the presence of S. thermophilus culture until the end of storage. S. thermophilus SJRP107 presented high potential for safety application in the production of Mozzarella cheese. Furthermore, considering the culture characteristics and their relationship with product quality, further studies could be helpful to determine their effect on the sensory characteristics of the cheese.
Assuntos
Queijo/microbiologia , Leite/microbiologia , Streptococcus thermophilus/crescimento & desenvolvimento , Streptococcus thermophilus/metabolismo , Animais , Búfalos , Queijo/análise , Qualidade de Produtos para o Consumidor , Fermentação , Microbiologia de Alimentos , Humanos , Streptococcus thermophilus/genética , Streptococcus thermophilus/isolamento & purificação , PaladarRESUMO
Streptococcus thermophilus ASCC 1275 has two chain length determining genes - epsC and epsD- in its eps gene cluster, and produces two times more EPS in sucrose medium than that in glucose and lactose. Hence, we investigated the influence of sugars (glucose, sucrose and lactose), at log phase (5 h) and stationary phase (10 h), on the global proteomics of S. thermophilus 1275 to understand the differentially expressed proteins (DEPs) during EPS production using isobaric tags for relative and absolute quantitation (iTRAQ)-based proteomic analysis. Among 98 DEPs in sucrose medium, most of them were mapped into EPS biosynthesis pathway and other related metabolisms. There was an upregulation of several proteins involved in sugar transport (phosphoenolpyruvate (PEP) phosphotransferase system), EPS assembly (epsG1D) and amino acid metabolism (methionine, cysteine/arginine metabolism) in sucrose medium. This study showed that increased EPS production in S. thermophilus 1275 requires a well-co-ordinated regulation of pathway involved in both EPS assembly and amino acid metabolism along with the availability of sugars. Thus, it provided valuable insights into the biosynthesis and regulation of EPS in S. thermophilus 1275, and potential gene targets for understanding high-EPS strains.
Assuntos
Proteínas de Bactérias/metabolismo , Polissacarídeos Bacterianos/biossíntese , Streptococcus thermophilus/metabolismo , Aminoácidos/metabolismo , Proteínas de Bactérias/genética , Transporte Biológico , Polissacarídeos Bacterianos/genética , Proteômica/métodos , Reprodutibilidade dos Testes , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Streptococcus thermophilus/crescimento & desenvolvimento , Açúcares/metabolismoRESUMO
This work was carried out to pursue a double objective: to improve the hygienic safety of cheeses produced from raw ewes' milk; and to produce a new typology of raw ewes' milk through the application of "Grana" technology for which the name "Gran Ovino" was chosen. With this in mind, raw milk from an individual farm was transformed under controlled conditions at a dairy pilot plant. The production technology included the partial skimming of the evening and morning milk mixture by cream surfacing and the addition of a natural whey starter cultures (NWSC) prepared with four selected Streptococcus thermophilus strains (PON6, PON244, PON261 e PON413). Ten microbial groups were investigated by plate counts from raw milk until ripened cheeses. Lactic acid bacteria (LAB) were in the range 104-105â¯CFU/ml before NWSC addition. After curdling, this group increased by 3 log cycles and was counted at 106â¯CFU/g after curd cooking. A rapid pH drop (to 6.05) was registered after almost 3â¯h from NWSC addition. The levels of members of the Enterobacteriaceae family were at about 103â¯CFU/ml in raw milk and decreased after curd cooking to 1 log cycle. A similar behavior was shown by the other undesired microbial groups and a complete disappearance of staphylococci was registered. The microbiological counts of 9-month ripened cheeses showed the dominance of LAB and undetectable levels of the undesired bacteria. MiSeq Illumina was applied to better investigate the bacterial composition of ripened cheeses and this technique evidenced that the majority of OTUs belonged to Lactobacillus and Streptococcus genera. The final cheeses were characterized by 67.65% dry matter of which 41.85% of fats and 47.02% of proteins. The main cheese fatty acids were palmitic, oleic and myristic acids and the saturated fatty acids/unsaturated fatty acids ratio was 2.17. Forty-one volatile compounds, including acids, esters, ketones, alcohols, aldehydes, phenols and one terpene were emitted from the cheese. Sensory evaluation showed a general appreciation for the new cheese product by judges.
Assuntos
Queijo/microbiologia , Tecnologia de Alimentos/métodos , Leite/microbiologia , Animais , Queijo/análise , Ácidos Graxos/análise , Feminino , Lactobacillus/crescimento & desenvolvimento , Ovinos , Streptococcus/crescimento & desenvolvimento , Streptococcus thermophilus/crescimento & desenvolvimento , Streptococcus thermophilus/metabolismo , Compostos Orgânicos Voláteis/análiseRESUMO
BACKGROUND: Recently, interest in the development of functional foods enriched with bioactive components has increased. Dairy products supplemented with tea extracts known for their health-promoting properties are good examples of such products. However, most of the scientific studies and applications focus on green tea. The present study was established to estimate the effect of Pu-erh tea supplementation on the viability of starter microorganisms and selected physico-chemical and sensory properties of probiotic ABT-yoghurt. METHODS: ABT-yoghurts (Lactobacillus acidophilus La-5, Bifidobacterium animalis ssp. lactis BB-12, Streptococcus thermophilus) were produced from cow’s milk with 0%, 5%, 10% or 15% (v/v) of Pu-erh tea infusion added before the fermentation stage. The products obtained were subjected to the following analyses one day after production (colour profile) and after 7, 14 and 21 days of cold storage: ferric reducing antioxidant power (FRAP) and anti-radical power (ARP) measured against DPPH radical, titratable acidity, pH, texture parameters (back extrusion test), viability of starter cultures and sensory quality (hedonic scale experiment). RESULTS: Pu-erh tea supplementation significantly enhanced the antioxidant potential of probiotic yoghurts as a 3–6.5-fold increase in FRAP and a 10–24-fold increase in ARP values were observed in comparison to plain ABT-yoghurt. Pu-erh tea slightly enhanced the viability of L. acidophilus and reduced the pH of probiotic yoghurts. Higher concentrations of Pu-erh tea caused decreased firmness and consistency while cohesiveness and index of viscosity remained unaffected upon supplementation. The addition of Pu-erh tea infusion modified the colour and sensory properties of the probiotic yoghurts but the sensory quality of the tea yoghurts was rated lower when compared to the plain one. Among all tea yoghurts, the one with 15% Pu-erh tea additive received the highest scores in sensory assessment. CONCLUSIONS: Pu-erh tea may be successfully applied as a functional additive to probiotic yoghurts, signifi- cantly enhancing the antioxidant properties of fermented milk and ensuring a high rate of starter bacteria viability during storage. However, the level of fortification must be carefully chosen as some doses negatively influence texture parameters and sensory quality.
Assuntos
Antioxidantes/farmacologia , Camellia sinensis , Fermentação , Manipulação de Alimentos/métodos , Probióticos , Chá , Iogurte/análise , Animais , Bifidobacterium animalis/crescimento & desenvolvimento , Bovinos , Suplementos Nutricionais , Feminino , Alimento Funcional , Humanos , Concentração de Íons de Hidrogênio , Lactobacillus acidophilus/crescimento & desenvolvimento , Viabilidade Microbiana , Leite/microbiologia , Extratos Vegetais/farmacologia , Reologia , Streptococcus thermophilus/crescimento & desenvolvimento , Paladar , Viscosidade , Iogurte/microbiologiaRESUMO
Understanding global changes of physiological processes at the molecular level during the growth of Streptococcus thermophilus is essential for the rational design of cultivation media and the optimization of bioprocesses. Transcriptomics and proteomics were combined to investigate the global changes at the transcript and protein level during the growth of S. thermophilus. The expression of 1396 genes (FDR ≤ 0.001) and 876 proteins (P < 0.05) changed significantly over time. The most remarkable growth phase dependent changes occurred in the late-lag phase and were related to heterofermentation, glycolysis, peptidoglycan biosynthesis, conversion between amino acids and stress response. The present results could provide theoretical guidance for high-cell-density culture, help design cultivation media, and help attain a high biomass of S. thermophilus.
Assuntos
Proteínas de Bactérias/genética , Streptococcus thermophilus/genética , Streptococcus thermophilus/metabolismo , Transcriptoma , Aminoácidos/metabolismo , Proteínas de Bactérias/metabolismo , Técnicas de Cultura Celular por Lotes , Fermentação , Perfilação da Expressão Gênica , Concentração de Íons de Hidrogênio , Proteômica , Streptococcus thermophilus/crescimento & desenvolvimentoRESUMO
Preparation of selenium-enriched probiotics and Se-enrichment of probiotic-fermented blended juices were performed and optimized using orthogonal test. Se content had a significant 13.0-fold increase by the addition of 1% Se-enriched Streptococcus thermophilus starters in juice fermentation. Chemical properties of fermented blended juices were determined. Reducing sugar content decreased significantly after fermentation, and the same downtrend was observed for free amino acids and organic acids, with lactic acid being an exception. Meanwhile, dynamic variation analysis of flavor components during the fermentation, and characteristic aroma-active compounds before and after fermentation were demonstrated by GC-MS and GC-O. Eleven aroma-active substances were identified from juices without fermentation, while 7 characteristic compounds were detected in fermented juices. Furthermore, potential correlations between chemical and flavor characteristics were explored based on multivariate statistical analysis. These results indicate that a potential Se-enriched fermented beverage was established, and the fermentation process led to differences in the chemical substrates and impact odorants.
Assuntos
Aromatizantes/análise , Sucos de Frutas e Vegetais/análise , Cromatografia Gasosa-Espectrometria de Massas , Selênio/química , Streptococcus thermophilus/crescimento & desenvolvimento , Aminoácidos/análise , Reatores Biológicos , Citrus sinensis/química , Citrus sinensis/metabolismo , Daucus carota/química , Daucus carota/metabolismo , Análise dos Mínimos Quadrados , Malus/química , Malus/metabolismo , Odorantes/análise , Análise de Componente Principal , Ziziphus/química , Ziziphus/metabolismoRESUMO
The current study investigates whether probiotic fermented milk (PFM) and yogurt consumption (YC) are related to both the ingested bacteria taxa and the overall gut microbiota (GM) composition in healthy adults. PFM and YC habits were analyzed in 260 subjects (51% male) by specific questionnaires, and the following groups were considered: (1) PFM groups: nonconsumers (PFM-NC, n = 175) and consumers (PFM, n = 85), divided as follows: Bifidobacterium-containing PFM (Bif-PFM; n = 33), Lactobacillus-containing PFM (Lb-PFM; n = 14), and mixed Bifidobacterium and Lactobacillus-containing PFM (Mixed-PFM; n = 38); (2) PFM-NC were classified as: yogurt nonconsumers (Y-NC; n = 40) and yogurt consumers (n = 135). GM was analyzed through 16S rRNA sequencing. PFM consumers showed higher Bifidobacteria taxa levels compared to NC, from phylum through to species. Specifically, Bif-PFM consumption was related to higher B. animalis levels (p < 0.001), whereas Lb-PFM consumption was associated to higher levels of Bifidobacterium (p < 0.045) and B. longum (p = 0.011). YC was related to higher levels of the yogurt starter Streptococcus thermophilus (p < 0.001). Lactobacilli and the overall GM were not related either to YC or PFM consumption. According to these results, healthy adults might benefit from PFM intake by increasing Bifidobacterium levels.