Production of organic flavor compounds by dominant lactic acid bacteria and yeasts from a traditional sorghum malt fermented beverage.

Single and mixed starter cultures of lactic acid bacteria (LAB): MNC20, MNC21, MNC24 and MNC34 and yeasts: MNC20Y and MNC21Y were used to produce , a fermented sorghum beverage. Microbial counts, pH, sugars, organic acids, and volatile compounds in starter culture and spontaneous fermentations were monitored during 48 hrs. Maximum counts of LAB (8.

Textural Properties of Beta-lactoglobulin - Sodium Alginate Mixed Gels at Large Scale Deformation.

The denaturation and gelling properties of mixed systems of β-lactoglobulin and sodium-alginate have been investigated as a function of alginate molecular weight, chemical composition, concentration, pH and ionic strength. Differential scanning calorimetry and small strain oscillatory measurements showed that denaturation temperature were lower than the gelling temperatures under the conditions examined. The denaturation temperatures were dependent on both pH and ionic strength, but unaffected by alginate concentration and type.

The dominant microbial community associated with fermentation of Obushera (sorghum and millet beverages) determined by culture-dependent and culture-independent methods.

Obushera includes four fermented cereal beverages from Uganda namely: Obutoko, Enturire, Ekitiribita and Obuteire, whose microbial diversity has not hitherto been fully investigated. Knowledge of the microbial diversity and dynamics in these products is crucial for understanding their safety and development of appropriate starter cultures for controlled industrial processing. Culture-dependent and culture-independent techniques including denaturating gradient gel electrophoresis (DGGE) and mixed DNA sequencing of polymerase chain reaction (PCR) amplified ribosomal RNA genes were used to study the bacteria and yeast diversity of Obushera.

Influence of cofermentation by amylolytic Lactobacillus plantarum and Lactococcus lactis strains on the fermentation process and rheology of sorghum porridge.

Amylolytic lactic acid bacteria (ALAB) can potentially replace malt in reducing the viscosity of starchy porridges. However, the drawback of using ALAB is their low and delayed amylolytic activity. This necessitates searching for efficient ALAB and strategies to improve their amylolytic activity.

Antibacterial peptides derived from caprine whey proteins, by digestion with human gastrointestinal juice.

Peptides in caprine whey were identified after in vitro digestion with human gastrointestinal enzymes in order to determine their antibacterial effect. The digestion was performed in two continuing steps using human gastric juice (pH 2·5) and human duodenal juice (pH 8) at 37°C. After digestion the hydrolysate was fractionated and 106 peptides were identified.

Flavor release of the tomato flavor enhancer, 2-isobutylthiazole, from whey protein stabilized model dressings.

A tomato flavor enhancer, 2-isobutylthiazole (IBT), was added (5 mg/kg) to dressings emulsified with either a whey protein concentrate-80 (WPC-80), a WPC-80 hydrolysate or β-lactoglobulin at high pressure (70 MPa) at either 20 or 75 °C. The short (2-4 min), high-temperature treatment left the proteins essentially unchanged. IBT addition gave a dominant, green tomato flavor that masked the intrinsic odor of the WPC-80 hydrolysate but enhanced bitter flavor.

The unconventional antimicrobial peptides of the classical propionibacteria.

The classical propionibacteria produce genetically unique antimicrobial peptides, whose biological activities are without equivalents, and to which there are no homologous sequences in public databases. In this review, we summarize the genetics, biochemistry, biosynthesis, and biological activities of three extensively studied antimicrobial peptides from propionibacteria. The propionicin T1 peptide constitutes a bona fide example of an unmodified general secretory pathway (sec)-dependent bacteriocin, which is bactericidal towards all tested species of propionibacteria except Propionibacterium freudenreichii.

Structural characteristic, pH and thermal stabilities of apo and holo forms of caprine and bovine lactoferrins.

Apo and holo forms of lactoferrin (LF) from caprine and bovine species have been characterized and compared with regard to the structural stability determined by thermal denaturation temperature values (T (m)), at pH 2.0-8.0.

Construction of a reporter vector system for in vivo analysis of promoter activity in Propionibacterium freudenreichii.

A beta-galactosidase reporter system for the analysis of promoter elements in Propionibacterium freudenreichii was designed. The pTD210 in vivo reporter vector was constructed using a promoterless lacZ gene from Bifidobacterium longum cloned into the pAMT1 plasmid. The utility of the pTD210 reporter vector was demonstrated by an investigation of six predicted promoters in P.

Propionibacterium jensenii produces the polyene pigment granadaene and has hemolytic properties similar to those of Streptococcus agalactiae.

The red polyene pigment granadaene was purified and identified from Propionibacterium jensenii. Granadaene has previously been identified only in Streptococcus agalactiae, where the pigment correlates with the hemolytic activity of the bacterium. A connection between hemolytic activity and the production of the red pigment has also been observed in P.

Autolysis of propionibacteria: detection of autolytic enzymes by renaturing SDS-PAGE and additional buffer studies.

Five strains of propionibacteria with 70-90% autolysis in sodium lactate broth (SLB) were studied by renaturing sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Several lytic bands ranging in size between 25 and 143 kDa were detected by using propionibacteria cells or cell walls as substrate in the gel. Four Propionibacterium freudenreichii strains showed similar autolytic-enzyme profiles, consisting of two autolytic bands, one with molecular mass 162 kDa and one in the range 123-143 kDa.

Use of DNA quantification to measure growth and autolysis of Lactococcus and Propionibacterium spp. in mixed populations.

Autolysis is self-degradation of the bacterial cell wall that results in the release of enzymes and DNA. Autolysis of starter bacteria, such as lactococci and propionibacteria, is essential for cheese ripening, but our understanding of this important process is limited. This is mainly because the current tools for measuring autolysis cannot readily be used for analysis of bacteria in mixed populations.

In vitro studies of the digestion of caprine whey proteins by human gastric and duodenal juice and the effects on selected microorganisms.

The in vitro digestion of caprine whey proteins was investigated by a two-step degradation assay, using human gastric juice (HGJ) at pH 2.5 and human duodenal juice (HDJ) at pH 7.5.

Total bacterial and species-specific 16S rDNA micro-array quantification of complex samples.

Aims: We describe a novel DNA-micro-array-based method that targets 16S rDNA to quantify changes in both the total bacterial DNA and the species-specific DNA composition.

Methods And Results: Quantifications were achieved by combining competitive PCR for quantifying total bacterial DNA with quantification of species-specific DNA composition based on signature 16S rDNA sequences. We constructed 11 different probes, which were evaluated on 21 different strains, in addition to complex samples.

Influence of controlled lactic fermentation on growth and sporulation of Bacillus cereus in milk.

The growth and sporulation of Bacillus cereus NVH 45 in a fermentor with controlled pH or simulated pH conditions were investigated. The study was carried out in a fermentor to measure the influence of a rapid and a slow lactic acid production on the inhibition of B. cereus in a controlled environment during the initial part of fermentation and to observe if other factors than lactic acid influenced the inhibition.

Production of antimicrobial metabolites by strains of Lactobacillus or Lactococcus co-cultured with Bacillus cereus in milk.

During co-culture of Lactobacillus (five strains) or Lactococcus (two strains) with Bacillus cereus, organic acids and other potentially antimicrobial metabolites are produced. Lactic acid was produced at very different rates by the lactic acid bacteria (LAB) and the final concentrations varied much, however, the crucial point of rapid pH reduction during the initial hours of fermentation coincides with lactic acid production. Moderate amounts of acetic acid were produced during fermentation and the final concentrations were much smaller compared to lactic acid.

Prevalence of the genes encoding propionicin T1 and protease-activated antimicrobial peptide and their expression in classical propionibacteria.

The purpose of this study was to investigate the frequency of production of the bacteriocin propionicin T1 and the protease-activated antimicrobial peptide (PAMP) and their corresponding genes in 64 isolates of classical propionibacteria. This study revealed that these genes are widespread in Propionibacterium jensenii and Propionibacterium thoenii but absent from the remaining species of classical propionibacteria that were studied. The pro-PAMP-encoding gene (pamA) was found in 63% of the P.

Inhibition of Bacillus cereus by strains of Lactobacillus and Lactococcus in milk.

The growth and death or survival of Bacillus cereus in sterile skimmed milk fermented with 18 different lactic acid bacteria (LAB) were investigated. B. cereus alone in milk reached about 10(7)-10(8) colony-forming units (cfu)/ml.

Cooperation between Lactococcus lactis and nonstarter lactobacilli in the formation of cheese aroma from amino acids.

In Gouda and Cheddar type cheeses the amino acid conversion to aroma compounds, which is a major process for aroma formation, is essentially due to lactic acid bacteria (LAB). In order to evaluate the respective role of starter and nonstarter LAB and their interactions in cheese flavor formation, we compared the catabolism of phenylalanine, leucine, and methionine by single strains and strain mixtures of Lactococcus lactis subsp. cremoris NCDO763 and three mesophilic lactobacilli.

Isolation, characterisation and identification of lactic acid bacteria from bushera: a Ugandan traditional fermented beverage.

One hundred and thirteen strains of lactic acid bacteria (LAB) were selected from 351 isolates from 15 samples of traditionally fermented household bushera from Uganda and also from laboratory-prepared bushera. Isolates were phenotypically characterised by their ability to ferment 49 carbohydrates using API 50 CHL kits and additional biochemical tests. Coliforms, yeasts and LAB were enumerated in bushera.

An antimicrobial peptide is produced by extracellular processing of a protein from Propionibacterium jensenii.

A protease-activated antimicrobial peptide (PAMP) and its inactive precursor were purified from the culture supernatant of Propionibacterium jensenii LMG 3032 and characterized at the molecular level. PAMP is a 64-amino-acid cationic peptide of 6,383 Da with physicochemical features similar to those of bacteriocins from gram-positive bacteria. This peptide displayed bactericidal activity against several propionibacteria and lactobacilli.

Growth and toxin profiles of Bacillus cereus isolated from different food sources.

Eleven strains of Bacillus cereus isolated from milk and meat products have been used to study growth and sporulation profiles in detail. Polymerase chain reaction (PCR) using primers detecting cold shock protein A gene signatures (cspA), showed that none of the strains were the newly suggested species in the B. cereus group, B.

Mineral-binding milk proteins and peptides; occurrence, biochemical and technological characteristics.

Minerals and trace elements in cow's milk occur as inorganic ions and salts or form complexes with proteins and peptides, carbohydrates, fats and small molecules. The main mineral binder or chelators of calcium are the caseins, alphas1-casein, alphas2-casein, beta-casein and kappa-casein, but also whey proteins and lactoferrin bind specific minerals like calcium, magnesium, zinc, iron, sodium and potassium. Less documented is the binding of trace elements.

Biochemical and genetic characterization of propionicin T1, a new bacteriocin from Propionibacterium thoenii.

A collection of propionibacteria was screened for bacteriocin production. A new bacteriocin named propionicin T1 was isolated from two strains of Propionibacterium thoenii. This bacteriocin shows no sequence similarity to other bacteriocins.

Autolysis of lactococci: detection of lytic enzymes by polyacrylamide gel electrophoresis and characterization in buffer systems.

Lactococcal strains were screened for bacteriolytic activity against Micrococcus luteus cells, lactococcal cells, and cell walls. Thirty strains were screened for bacteriolytic activity against cells and cell walls incorporated into agar medium. Enzymes from all strains hydrolyzed the substrates; however, the activity against Micrococcus cells was much higher than against Lactococcus cells or cell walls.