RESUMEN
Ice cream manufacture commonly results in the accumulation of wasted product that contains valuable food-grade quality components, including fat, carbohydrates, and protein. Methods have been developed for recovering the fat from this waste stream, but this results in the generation of a co-product rich in fermentable carbohydrates. This study aimed to investigate the potential for using this co-product as a fermentation substrate for production of antimicrobial peptides, called bacteriocins, by dairy starter cultures. Results showed that Streptococcus thermophilus B59671 and Lactococcus lactis 11454 produced the broad-spectrum bacteriocins thermophilin 110 and nisin, respectively, when the fermentation substrate was melted ice cream, or a co-product generated by a modified butter churning technique. Bacteriocin production varied depending on the brand and variety of vanilla ice cream used in this study. When an alternate enzyme-assisted fat extraction technique was used, S. thermophilus metabolism was impaired within the resulting co-product, and thermophilin 110 production was not observed. Lactococcus lactis was still able to grow in this co-product, but antimicrobial activity was not observed. Results from this study suggest the co-product generated when using the churning technique is a better choice to use as a base medium for future studies to optimize bacteriocin production.
Asunto(s)
Bacteriocinas , Fermentación , Helados , Lactobacillales , Bacteriocinas/metabolismo , Bacteriocinas/biosíntesis , Lactobacillales/metabolismo , Streptococcus thermophilus/metabolismo , Lactococcus lactis/metabolismoRESUMEN
OBJECTIVE: Thermophilin 110, a bacteriocin produced by Streptococcus thermophilus B59671, inhibited planktonic growth and biofilm formation of Cutibacterium acnes, a commensal skin bacterium associated with the inflammatory disease, acne vulgaris, and more invasive deep tissue infections. RESULTS: Thermophilin 110 prevented planktonic growth of C. acnes at a concentration ≥ 160 AU mL-1; while concentrations ≥ 640 AU mL-1 resulted in a > 5 log reduction in viable planktonic cell counts and inhibited biofilm formation. Arabinoxylan (AX) and sodium alginate (SA) hydrogels were shown to encapsulate thermophilin 110, but as currently formulated, the encapsulated bacteriocin was unable to diffuse out of the gel and inhibit the growth of C. acnes. Hydrogels were also used to encapsulate S. thermophilus B59671, and inhibition zones were observed against C. acnes around intact SA gels, or S. thermophilus colonies that were released from AX gels. CONCLUSIONS: Thermophilin 110 has potential as an antimicrobial for preventing C. acnes infections and further optimization of SA and AX gel formulations could allow them to serve as delivery systems for bacteriocins or bacteriocin-producing probiotics.
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Bacteriocinas , Piel , Alginatos , Bacteriocinas/farmacología , Agregación Celular , HidrogelesRESUMEN
Consumers' growing interest in fermented dairy foods necessitates research on a wide array of lactic acid bacterial strains to be explored and used. This study aimed to investigate the differences in the proteolytic capacity of Lactobacillus helveticus strains B1929 and ATCC 15009 on the fermentation of commercial ultra-pasteurized (UHT) skim milk and reconstituted nonfat dried milk powder (at a comparable protein concentration, 4%). The antihypertensive properties of the fermented milk, measured by angiotensin-I-converting enzyme inhibitory (ACE-I) activity, were compared. The B1929 strain lowered the pH of the milk to 4.13 ± 0.09 at 37°C after 24 h, whereas ATCC 15009 needed 48 h to drop the pH to 4.70 ± 0.18 at 37°C. Two soluble protein fractions, one (CFS1) obtained after fermentation (acidic conditions) and the other (CFS2) after the neutralization (pH 6.70) of the pellet from CFS1 separation, were analyzed for d-/l-lactic acid production, protein concentration, the degree of protein hydrolysis, and ACE-I activity. The CFS1 fractions, dominated by whey proteins, demonstrated a greater degree of protein hydrolysis (7.9%) than CFS2. On the other hand, CFS2, mainly casein proteins, showed a higher level of ACE-I activity (33.8%) than CFS1. Significant differences were also found in the d- and l-lactic acid produced by the UHT milk between the 2 strains. These results attest that milk casein proteins possessed more detectable ACE-I activity than whey fractions, even without a measurable degree of hydrolysis. Findings from this study suggest that careful consideration must be given when selecting the bacterial strain and milk substrate for fermentation.
Asunto(s)
Lactobacillus helveticus , Leche , Animales , Leche/química , Lactobacillus helveticus/química , Hidrólisis , Polvos/análisis , Caseínas/análisis , Temperatura , Inhibidores de la Enzima Convertidora de Angiotensina/análisis , Proteínas de la Leche/análisis , Fermentación , Proteína de Suero de Leche/análisis , Angiotensinas/análisis , Angiotensinas/metabolismoRESUMEN
BACKGROUND: Probiotics have been reported to reduce total cholesterol levels in vitro, but more evidence is needed to determine the clinical relevance of this activity. Chinese traditional fermented pickles are a good source of lactic acid bacteria. Therefore, pickle samples were collected for screening lactic acid bacteria based on their ability to survive stresses encountered during gastrointestinal passage and cholesterol reducing potency. RESULTS: Seventy five lactic acid bacteria strains were isolated from 22 fermented pickles. From these bacteria, Lactobacillus plantarum E680, showed the highest acid (85.25%) and bile tolerance (80.79%). It was sensitive to five of the eight antibiotics tested, inhibited the growth of four pathogenic bacteria, and reduced the total cholesterol level by 66.84% in broth culture. In vivo testing using hypercholesterolemic mice fed high-fat emulsion, independent of food intake, found that L. plantarum E680 suppressed body weight gain and reduced total cholesterol and low-density lipoprotein cholesterol levels, with no effect on high-density lipoprotein cholesterol. CONCLUSIONS: Chinese traditional fermented pickles are a good source for probiotics. L. plantarum E680, isolated from pickles, was acid and bile tolerant, sensitive to antibiotics, and reduced cholesterol levels both in vitro and in vivo. Based on these results, L. plantarum E680 may have potential as a novel probiotic for the development of cholesterol-lowering functional food.
Asunto(s)
Hipercolesterolemia/tratamiento farmacológico , Lactobacillus plantarum/fisiología , Probióticos , Ácidos/metabolismo , Animales , Antibacterianos/farmacología , Antibiosis , Anticolesterolemiantes/farmacología , Anticolesterolemiantes/uso terapéutico , Ácidos y Sales Biliares/metabolismo , Peso Corporal/efectos de los fármacos , Cucumis sativus , Alimentos Fermentados/microbiología , Hipercolesterolemia/sangre , Hipercolesterolemia/patología , Lactobacillales/efectos de los fármacos , Lactobacillales/aislamiento & purificación , Lactobacillales/fisiología , Lactobacillus plantarum/efectos de los fármacos , Lactobacillus plantarum/aislamiento & purificación , Lípidos/sangre , Ratones , Probióticos/administración & dosificación , Probióticos/farmacologíaRESUMEN
OBJECTIVES: To demonstrate that S. thermophilus ST109 produces an antimicrobial peptide encoded within the bacteriocin-like peptide (blp) gene cluster, and to determine its broad spectrum activity against potential human pathogens. RESULTS: Analysis of the cell free supernatant (CFS) revealed that antimicrobial activity was associated with the presence of a heat-stable peptide of approximately 5-6 kDa; and activity was lost after protease treatment or exposure to α-amylase. Deletion of blpC, which encodes a quorum sensing induction peptide, resulted in a loss of antimicrobial activity showing that thermophilin 109 was encoded within the blp gene cluster of ST109. Sequencing of the ST109 blp gene cluster showed 90% and 99% identity to clusters previously characterized in S. thermophilus strains LMD-9 and ST106, both of which are unable to naturally produce their bacteriocins. Real-time qPCR showed that blpC and blpD were expressed approximately 24 and 100-fold higher in ST109 as compared to strain LMD-9; and broad spectrum activity was demonstrated against lactobacilli, enterococci and the human pathogen Streptococcus pyogenes. CONCLUSIONS: The high level of similarity observed between the ST109 and ST106 blp gene clusters at the nucleic acid level suggests bacteriocin expression may be regulated by factors encoded elsewhere on the chromosome. Activity against E. faecalis and S. pyogenes suggest S. thermophilus ST109 could be used for food safety and probiotic applications.
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Bacteriocinas/genética , Bacteriocinas/farmacología , Familia de Multigenes , Streptococcus thermophilus/metabolismo , Regulación Bacteriana de la Expresión Génica , Humanos , Pruebas de Sensibilidad Microbiana , Peso Molecular , Estabilidad Proteica , Percepción de Quorum , Análisis de Secuencia de ADN , Streptococcus pyogenes/efectos de los fármacos , Streptococcus thermophilus/genéticaRESUMEN
An 8-AA (8mer) fragment (PFPEVFGK) of a known antihypertensive peptide derived from bovine αS1-casein (C12 antihypertensive peptide) was synthesized by microwave-assisted solid-phase peptide synthesis and purified by reverse phase HPLC. Its ability to inhibit angiotensin-converting enzyme (ACE) was assessed and compared with that of the parent 12mer peptide (FFVAPFPEVFGK) to determine the effect of truncating the sequence on overall hypotensive activity. The activity of the truncated 8mer peptide was found to be almost 1.5 times less active than that of the 12mer, with ACE-inhibiting IC50 (half-maximal inhibitory concentration) values of 108 and 69µM, for the 8mer and 12mer, respectively. Although the 8mer peptide is less active than the original 12mer peptide, its overall activity is comparable to activities reported for other small proteins that elicit physiological responses within humans. These results suggest that microbial degradation of the 12mer peptide would not result in a complete loss of antihypertensive activity if used to supplement fermented foods and that the stable 8mer peptide could have potential as a blood pressure-lowering agent for use in functional foods.
Asunto(s)
Inhibidores de la Enzima Convertidora de Angiotensina/química , Antihipertensivos , Secuencia de Aminoácidos , Aminoácidos/farmacología , Animales , Presión Sanguínea/efectos de los fármacos , Bovinos , Péptidos/químicaRESUMEN
The effect of refrigeration on bacterial communities within raw and pasteurized buffalo milk was studied using high-throughput sequencing. High-quality samples of raw buffalo milk were obtained from 3 dairy farms in the Guangxi province in southern China. Five liters of each milk sample were pasteurized (72°C; 15 s); and both raw and pasteurized milks were stored at refrigeration temperature (1-4°C) for various times with their microbial communities characterized using the Illumina Miseq platform (Novogene, Beijing, China). Results showed that both raw and pasteurized milks contained a diverse microbial population and that the populations changed over time during storage. In raw buffalo milk, Lactococcus and Streptococcus dominated the population within the first 24h; however, when stored for up to 72h the dominant bacteria were members of the Pseudomonas and Acinetobacter genera, totaling more than 60% of the community. In pasteurized buffalo milk, the microbial population shifted from a Lactococcus-dominated community (7d), to one containing more than 84% Paenibacillus by 21d of storage. To increase the shelf-life of buffalo milk and its products, raw milk needs to be refrigerated immediately after milking and throughout transport, and should be monitored for the presence of Paenibacillus. Results from this study suggest pasteurization should be performed within 24h of raw milk collection, when the number of psychrotrophic bacteria are low; however, as Paenibacillus spores are resistant to pasteurization, additional antimicrobial treatments may be required to extend shelf-life. The findings from this study are expected to aid in improving the quality and safety of raw and pasteurized buffalo milk.
Asunto(s)
Leche/microbiología , Refrigeración , Animales , Búfalos , China , Microbiología de Alimentos , TemperaturaRESUMEN
OBJECTIVE: To improve the process for the production of milk-derived antihypertensive peptides, including a 12-residue peptide (FFVAPFPECVGK) from αS1-casein. RESULTS: A synthetic gene encoding this peptide was cloned within the pediocin operon, replacing the nucleic acid sequence encoding the mature pediocin peptide (papA) and resulting in a translational fusion between the pediocin leader peptide and the 12-residue hypotensive (C-12) peptide. The recombinant operon was subsequently cloned immediately downstream of the nisA promoter to allow for inducible gene expression within Streptococcus thermophilus ST128, Lactococcus lactis subsp. lactis ML3 and Lactobacillus casei C2. RT-PCR was used to confirm recombinant gene expression in complex medium; and SDS-PAGE analysis showed that the pediocin secretion machinery, encoded by papC and papD, allowed for secretion of the recombinant peptide from both L. lactis ML3 and L. casei C2 in a chemically defined medium. CONCLUSION: The use of a nisin as a "food-grade" inducer molecule, and generally-regarded-as-safe LAB species suggests that this system could be used for the production of functional food ingredients.
Asunto(s)
Antihipertensivos/metabolismo , Caseínas/metabolismo , Lactobacillaceae/genética , Nisina/metabolismo , Fragmentos de Péptidos/metabolismo , Proteínas Recombinantes/metabolismo , Secuencia de Aminoácidos , Animales , Antihipertensivos/química , Secuencia de Bases , Caseínas/genética , Bovinos , Clonación Molecular , Lactobacillaceae/metabolismo , Datos de Secuencia Molecular , Fragmentos de Péptidos/química , Fragmentos de Péptidos/genética , Plásmidos/genética , Proteínas Recombinantes/química , Proteínas Recombinantes/genéticaRESUMEN
Native microflora in raw milk cheeses, including the Mexican variety Queso Chihuahua, contribute to flavor development through degradation of milk proteins. The effects of proteolysis were studied in four different brands of Mexican Queso Chihuahua made from raw milk. All of the cheeses were analyzed for chemical and sensory characteristics. Sensory testing revealed that the fresh cheeses elicited flavors of young, basic cheeses, with slight bitter notes. Analysis by gel electrophoresis and reverse phase-high performance liquid chromatography (RP-HPLC) revealed that the Queseria Blumen (X) and Queseria Super Fino (Z) cheeses show little protein degradation over time while the Queseria America (W) and Queseria Lago Grande (Y) samples are degraded extensively when aged at 4 °C for 8 weeks. Analysis of the mixture of water-soluble cheese proteins by mass spectrometry revealed the presence of short, hydrophobic peptides in quantities correlating with bitterness. All cheese samples contained enterococcal strains known to produce enterocins. The W and Y cheese samples had the highest number of bacteria and exhibited greater protein degradation than that observed for the X and Z cheeses.
RESUMEN
Streptococcus thermophilus strain B59671 naturally produces thermophilin 110, a broad-spectrum bacteriocin encoded within the bacteriocin-like peptide (blp) gene cluster, and thermophilin 13 from a separate chromosomal locus. Analysis of the blp gene cluster revealed two genes, blpU and blpK, as potentially encoding bacteriocins. Deletion of blpK from the B59671 chromosome did not result in a loss of antimicrobial activity against either S. thermophilus ST113 or Pediococcus acidilactici F. A deletion mutant of blpU could not be generated in B59671, but the mature BlpU peptide obtained through overexpression in E. coli BL21 or chemical synthesis inhibited the growth of S. thermophilus strains, Streptococcus mutans UA159, P. acidilactici F, and Listeria innocua GV9 L-S, evidencing as a broad-spectrum bacteriocin that does not require modification for activity. This study also showed that the transcription of blpU was approximately 16-fold higher in B59671 than in an induced culture of S. thermophilus LMD-9, which produces a blp-encoded bacteriocin. The increased expression of BlpU in B59671 may explain the unique antimicrobial spectrum associated with this strain. Additionally, it was shown that a blpC deletion mutant of B59671, which prevents expression of BlpU and BlpK, inhibited the growth of other S. thermophilus strains and Bacillus cereus, suggesting that thermophilin 13 produced by B59671 possessed both intra- and interspecies antimicrobial activity. While this study confirmed that BlpU can function as an independent antimicrobial peptide, further studies are required to determine if BlpK can function independently as a broad-spectrum antimicrobial.
RESUMEN
Streptococcus thermophilus B59671 produces a bacteriocin with anti-pediococcal activity, but genes required for its production are not characterized. Genome sequencing of S. thermophilus has identified a genetic locus encoding a quorum sensing (QS) system that regulates production of class II bacteriocins. However, in strains possessing this gene cluster, production of bacteriocin like peptides (Blp) was only observed when excess pheromone was provided. PCR analysis revealed this strain possessed blpC, which encodes the 30-mer QS pheromone. To investigate if BlpC regulates bacteriocin production in S. thermophilus B59671, an integrative vector was used to replace blpC with a gene encoding for kanamycin resistance and the resulting mutant did not inhibit the growth of Pediococcus acidilactici. Constitutive expression of blpC from a shuttle vector restored the bacteriocin production, confirming the blp gene cluster is essential for bacteriocin activity in S. thermophilus B59671.
Asunto(s)
Bacteriocinas/metabolismo , Regulación Bacteriana de la Expresión Génica , Streptococcus thermophilus/genética , Streptococcus thermophilus/metabolismo , Eliminación de Gen , Prueba de Complementación Genética , Vectores Genéticos , Familia de Multigenes , Pediococcus/efectos de los fármacos , Feromonas/genética , Feromonas/metabolismoRESUMEN
Bacteriocin production in Streptococcus thermophilus is regulated by cell density-dependent signaling molecules, including BlpC, which regulates transcription from within the bacteriocin-like peptide (blp) gene cluster. In some strains, such as S. thermophilus ST106, this signaling system does not function properly, and BlpC must be supplied exogenously to induce bacteriocin production. In other strains, such as S. thermophilus B59671, bacteriocin (thermophilin 110 in strain B59671) production occurs naturally. Here, transcriptomic analyses were used to compare global gene expression within ST106 in the presence or absence of synthetic BlpC and within B59671 to determine if BlpC regulates the expression of genes outside the blp cluster. Real-time semi-quantitative PCR was used to find genes differentially expressed in the absence of chromosomal blpC in the B59671 background. Growth curve experiments and bacteriocin activity assays were performed with knockout mutants and BlpC supplementation to identify effects on growth and bacteriocin production. In addition to the genes involved in bacteriocin production, BlpC affected the expression of several transcription regulators outside the blp gene cluster, including a putative YtrA-subfamily transcriptional repressor. In strain B59671, BlpC not only regulated the expression of thermophilin 110 but also suppressed the production of another bacteriocin, thermophilin 13, and induced the same YtrA-subfamily transcriptional repressor identified in ST106. Additionally, it was shown that the broad-spectrum antimicrobial activity associated with strain B59671 was due to the production of thermophilin 110, while thermophilin 13 appears to be a redundant system for suppressing intraspecies growth. BlpC production or induction negatively affected the growth of strains B59671 and ST106, revealing selective pressure to not produce bacteriocins that may explain bacteriocin production phenotype differences between S. thermophilus strains. This study identifies additional genes regulated by BlpC and assists in defining conditions to optimize the production of bacteriocins for applications in agriculture or human and animal health.
RESUMEN
Enterococci constitute a significant component of the lactic acid bacteria normally present in the intestinal microflora and include strains that produce bacteriocins. The genetic determinants for durancin GL in Enterococcus durans 41D were identified on the 8347 bp plasmid pDGL1 by plasmid curing experiments. pDGL1 contained nine putative ORFs, with ORF1 and ORF2 encoding plasmid replication proteins, and ORF3 and ORF6 showing high similarity to genes encoding mobilization proteins. The predicted protein encoded by ORF4 showed 74â% identity to BacA, a bacteriocin produced by Enterococcus faecalis. The deduced DurA protein contained the conserved motif YYGNG, suggesting that durancin GL is a typical subclass IIa bacteriocin. ORF5 was shown to share 85â% identity to the immunity protein BacB of Enterococcus faecalis. ORF9 displayed 87â% sequence identity to a conserved hypothetical protein of unknown function. To further clarify the minimum requirement for durancin GL production, a 547 bp fragment containing the durAB gene was fitted with the Streptococcus thermophilus P(2201) promoter and then subcloned and heterologously expressed in S. thermophilus ST128. The result demonstrated that the cloned fragment contained all the genetic components required for durancin GL production.
Asunto(s)
Bacteriocinas/genética , Enterococcus/genética , Plásmidos/genética , Secuencia de Aminoácidos , Bacteriocinas/biosíntesis , Bacteriocinas/química , Secuencia de Bases , Queso/microbiología , Enterococcus/química , Enterococcus/aislamiento & purificación , Enterococcus/metabolismo , Datos de Secuencia Molecular , Sistemas de Lectura Abierta , Plásmidos/química , Plásmidos/metabolismo , Alineación de SecuenciaRESUMEN
The integrative vector, pINTRS, was used to transfer glutamate decarboxylase (GAD) activity to Streptococcus thermophilus ST128 thereby allowing for the production of γ-aminobutyric acid (GABA). In pINTRS, the gene encoding glutamate decarboxylase, gadB, was flanked by DNA fragments homologous to a S. thermophilus pseudogene to allow for integration at a non-essential locus on the chromosome. Screening techniques confirmed the insertion of gadB with either its endogenous promoter or the S. thermophilus P2201 promoter, resulting in the generation of recombinant strains, ST128/gadB or ST128/P2201-gadB. Following the integration event unwanted plasmid DNA, specifically the erythromycin resistance gene, was eliminated from the recombinant strains. Based on the production of GABA, activities of GAD for ST128/gadB and ST128/P2201-gadB were 30.6 ± 6 and 27.9 ± 7.2 µM/mg dry cell wt, respectively.
Asunto(s)
Glutamato Descarboxilasa/genética , Glutamato Descarboxilasa/metabolismo , Ingeniería Metabólica , Recombinación Genética , Streptococcus thermophilus/genética , Streptococcus thermophilus/metabolismo , Ácido gamma-Aminobutírico/metabolismo , Vectores Genéticos , Mutagénesis Insercional , Plásmidos , Regiones Promotoras Genéticas , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismoRESUMEN
Electrospinning has been proposed as a method to encapsulate and preserve bioactive compounds in nanofibrous mats to ensure their delivery and associated health benefits when consumed directly or added to a food formulation. In previous work, we demonstrated the production of edible fibers to form mats of both calcium (CaCAS) and sodium (NaCAS) caseinate-pullulan (PUL), with the polysaccharide PUL added as a carrier to facilitate molecular entanglement for fiber formation. In this study, we determined the viability of the probiotic bacteria, Lactobacillus rhamnosus GG (LGG), used as a model bacterium, in mats of CaCAS-PUL and NaCAS-PUL. Electrospinning of aqueous solutions at room temperature (21 ± 1°C) of 15% (wt/wt) CaCAS and NaCAS mixed with 15% (wt/wt) PUL, with a 1:1 ratio of CAS:PUL, resulted in fibrous mats with average fiber diameter sizes of 233 ± 20 and 244 ± 21 nm, respectively, as determined by scanning electron microscopy. Addition of LGG in the amounts of 9.3 and 9.0 log10 cfu/mL to the CaCAS-PUL and NaCAS-PUL solutions before electrospinning resulted in average fiber diameter sizes of 212 ± 14 and 286 ± 16 nm, respectively. The LGG was found to be distributed within the CaCAS-PUL and NaCAS-PUL fibers. The addition of LGG increased the shear viscosity and conductivity of the CaCAS-PUL solution, enhancing molecular entanglement and resulting in thinner fibers. For NaCAS, LGG increased the conductivity but reduced shear viscosity. Adjustment of the NaCAS-PUL composition would be needed to optimize conditions for thinner fibers. The numbers of viable LGG recovered from the CaCAS-PUL and NaCAS-PUL nanofibrous mats after electrospinning were 9.5 and 9.6 log10 cfu/g, respectively, proving that the electrospinning conditions used were capable of supporting probiotic encapsulation. These results demonstrate that food-grade electrospun fibrous mats can be used to develop functional foods with delivery of probiotics to improve human or animal health.
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Listeria monocytogenes is a significant foodborne health hazard in many products and may survive and grow when making fermented meat sausages. The objective of this study was to investigate the competition between lactic acid bacteria (LAB) and L. monocytogenes during simultaneous fermentation and drying (SFD) of meat sausages. Sausages made from irradiated ground beef (90% lean), salt, sugar, and sodium nitrite were inoculated with a 4-stain cocktail of LAB (2 Lactobacillus plantarum and 2 Lb. brevis strains) and a 5-strain cocktail of L. monocytogenes, individually or in combination, and incubated (30 °C, relative humidity 76%) for 5 days to undergo SFD. The changes in the populations of LAB and L. monocytogenes were monitored to determine the growth kinetics and examine the competitive growth between the two. L. monocytogenes grew in the sausage samples unhindered without LAB but was suppressed by LAB during SFD. The interaction between LAB and L. monocytogenes could be described by a modified Lotka-Volterra equation. The decreases of pH and aw in sausages could be related to the SFD time using segmented linear models. The competition model could accurately predict the growth of LAB and L. monocytogenes during SFD and may be used to improve the safety of semi-dry and dry fermented meat sausages.
Asunto(s)
Lactobacillales , Listeria monocytogenes , Animales , Bovinos , Fermentación , Microbiología de Alimentos , CarneRESUMEN
Numerous health benefits have been reported from the consumption of cranberry-derived products, and recent studies have identified bioactive polysaccharides and oligosaccharides from cranberry pomace. This study aimed to further characterize xyloglucan and pectic oligosaccharide structures from pectinase-treated cranberry pomace and measure the growth and short-chain fatty acid production of 86 Lactobacillus strains using a cranberry oligosaccharide fraction as the carbon source. In addition to arabino-xyloglucan structures, cranberry oligosaccharides included pectic rhamnogalacturonan I which was methyl-esterified, acetylated and contained arabino-galacto-oligosaccharide side chains and a 4,5-unsaturated function at the non-reducing end. When grown on cranberry oligosaccharides, ten Lactobacillus strains reached a final culture density (ΔOD) ≥ 0.50 after 24 h incubation at 32 °C, which was comparable to L. plantarum ATCC BAA 793. All strains produced lactic, acetic, and propionic acids, and all but three strains produced butyric acid. This study demonstrated that the ability to metabolize cranberry oligosaccharides is Lactobacillus strain specific, with some strains having the potential to be probiotics, and for the first time showed these ten strains were capable of growth on this carbon source. The novel cranberry pectic and arabino-xyloglucan oligosaccharide structures reported here combined with the Lactobacillus strains that can metabolize cranberry oligosaccharides and produce short-chain fatty acids, have excellent potential as health-promoting synbiotics.
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Dental caries continues to occur in both children and adults worldwide resulting in significant economic burden, and consumers have expressed interest in natural products that can prevent these recurrent infections. In this study, S. thermophilus B59671, which produces thermophilin 110, was shown to inhibit the growth of S. mutans UA159. A thermophilin concentration ≥ 80 AU ml-1 prevented the growth of S. mutans UA159 in batch culture, while ≥ 160 AU ml-1 was required to prevent biofilm growth. Co-culturing S. thermophilus B59671 and S. mutans UA159 also resulted in impaired biofilm growth. Thermophillin 110 was also shown inhibit additional S. mutans strains and commensal oral streptococci at higher concentrations (640-1280 AU ml-1). These results suggest that thermophilin 110 could be used as a natural antimicrobial in oral care products and support the need for additional studies to assess the probiotic potential of S. thermophilus B59671.
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Novel probiotic strains that can ferment prebiotics are important for functional foods. The utilization of prebiotics is strain specific, so we screened 86 Lactobacillus strains and compared them to Bifidobacterium breve 2141 for the ability to grow and produce SCFA when 1% inulin or fructo-oligosaccharides (FOS) were provided as the carbon source in batch fermentations. When grown anaerobically at 32 °C, ten Lactobacillus strains grew on both prebiotic substrates (OD600 ≥ 1.2); while Lactobacillus coryniformis subsp. torquens B4390 grew only in the presence of inulin. When the growth temperature was increased to 37 °C to simulate the human body temperature, four of these strains were no longer able to grow on either prebiotic. Additionally, L. casei strains 4646 and B441, and L. helveticus strains B1842 and B1929 did not require anaerobic conditions for growth on both prebiotics. Short-chain fatty acid analysis was performed on cell-free supernatants. The concentration of lactic acid produced by the ten Lactobacillus strains in the presence of prebiotics ranged from 73-205 mM. L. helveticus B1929 produced the highest concentration of acetic acid ~19 mM, while L. paraplantarum B23115 and L. paracasei ssp. paracasei B4564 produced the highest concentrations of propionic (1.8-4.0 mM) and butyric (0.9 and 1.1 mM) acids from prebiotic fermentation. L. mali B4563, L. paraplantarum B23115 and L. paracasei ssp. paracasei B4564 were identified as butyrate producers for the first time. These strains hold potential as synbiotics with FOS or inulin in the development of functional foods, including infant formula.
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Yak yogurt, one of the naturally fermented dairy products prepared by local herdsmen in the Qinghai-Tibet Plateau, contains a diverse array of microorganisms. We isolated and identified a novel Streptococcus thermophilus strain, ZJUIDS-2-01, from the traditional yak yogurt. We further purified and carried out detailed structural, physiochemical, and bioactivity studies of an exopolysaccharide (EPS-3A) produced by S. thermophilus ZJUIDS-2-01. The weight-average molecular weight (Mw) of EPS-3A was estimated to be 1.38 × 106 Da by High-Performance Gel Permeation Chromatography (HPGPC). The monosaccharide analysis established its composition to be glucose, galactose, N-acetyl-D-galactosamine, and rhamnose in a ratio of 5.2:2.5:6.4:1.0. The molecular structure of EPS-3A was determined by the combination of permethylation analysis, FT-IR, and NMR spectroscopic techniques. The ζ-potential measurements indicated that EPS-3A had a pKa value of ~4.40. The DSC yielded a melting point (Tm) of 80.4 °C and enthalpy change (ΔH) of 578 J/g for EPS-3A, comparable to those of the xanthan gum (XG), a commercial EPS. EPS-3A exhibited better O/W emulsion stability and flocculating capacity than XG. Furthermore, it also demonstrated similar antioxidant activity to XG and promising in vitro antibacterial properties. This work evidenced that EPS-3A derived from S. thermophilus ZJUIDS-2-01 holds the potential for food and industrial applications.