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At least 1,729 records · Page 96Linked to original sources
PubMed2000

Flavor enhancement of reduced fat cheddar cheese using an integrated culturing system.

Mild cheese flavor in reduced fat Cheddar cheese was enhanced by using an integrated starter culture system. Three cultures, Lactococcus lactis subsp. cremoris SK11, L. lactis subsp. lactis biovar. diacetylactis JVI, and Lactobacillus casei 7A, were carefully selected to obtain a nonbitter, mildly acid, buttery flavored cheese. Cheeses were produced from all possible combinations of these cultures with the constraint that L. lactis subsp. cremoris SK11 was used as the primary acid-producing culture. Cheeses made with SK11 were compared to cheeses produced using an L. lactis subsp. cremoris commercial starter culture. Cheeses were ripened for 150 days and periodically sampled for chemical, microbiological, and sensory analysis. Cheeses produced with L. lactis subsp. cremorisSK11 had substantially lower bitterness intensity than the cheeses produced with commercial starter culture. L. lactis subsp. lactis biovar. diacetylactis JVI significantly increased diacetylacetoin and acetate concentrations. Sensory results indicate that these cheeses had increased buttery (diacetyl) flavor.

Cheese↗
PubMed2004

Lipid-mediated light activation of a mechanosensitive channel of large conductance.

This paper describes the reversible activation of a mechanosensitive channel via a light-sensitive lipid mimic. For these experiments, the mechanosensitive channel of large conductance (MscL) protein from Lactococcus lactis and Escherichia coli was reconstituted in lipid bilayers composed of 80 mol % 1,2-dioleoyl-sn-glycero-3-phosphocholine and 20 mol % di-(5-[[4-(4-butylphenyl)azo]phenoxy]pentyl)phosphate (4-Azo-5P). Light-induced isomerization of the azobenzene moiety of 4-Azo-5P from trans to cis was used to activate MscL.

Azo Compounds↗
PubMed2006

Investigations of the antibacterial properties of ciprofloxacin@SiO2.

The antibacterial activity of ciprofloxacin-encapsulated silica nanoshells synthesized from gold@silica core-shell nanoparticles has been investigated. The minimum inhibitory concentration of the material was found using the agar dilution method, and it showed better antibacterial activity compared to free ciprofloxacin in the case of Escherichia coli DH5, whereas the same activity was found for Lactococcus lactis MG 1363. Hydrophobicity measurements carried out in an octanol-water mixture suggested that ciprofloxacin@SiO2 is distributed almost equally in the aqueous and nonaqueous phases. The kinetics of the uptake of ciprofloxacin@SiO2 was compared with that of free ciprofloxacin. Fluorescence imaging studies carried out using fluorescein isothiocyanate@SiO2 showed that the nanoshells enter the bacterial cell. The uptake of silica shells has been probed by transmission electron microscopy also.

Anti-Bacterial Agents↗
PubMed2006

Decaspirones F-I, bioactive secondary metabolites from the saprophytic fungus Helicoma viridis.

Decaspirones F-H (1-3), three new spirobisnaphthalene derivatives, and one new non-spirobisnaphthalene, decaspirone I (4), have been isolated from cultures of an isolate of the saprophytic fungus Helicoma viridis. The structures of these compounds were determined mainly by analysis of their NMR spectroscopic data. The absolute configuration of decaspirone F (1) was established by X-ray crystallographic analysis of its mono-bromobenzoate derivative. In standard disk assays, compounds 1-4 showed modest activity against Pseudomonas aeruginosa (multiple antibiotic-resistant strain, ATCC 27853), and decaspirone G (2) also displayed activity against Lactococcus lacti (PCM 2379).

Anti-Bacterial Agents↗
PubMed1997

The role of transport processes in survival of lactic acid bacteria. Energy transduction and multidrug resistance.

Lactic acid bacteria play an essential role in many food fermentation processes. They are anaerobic organisms which obtain their metabolic energy by substrate phosphorylation. In addition three secondary energy transducing processes can contribute to the generation of a proton motive force: proton/substrate symport as in lactic acid excretion, electrogenic precursor/product exchange as in malolactic and citrolactic fermentation and histidine/histamine exchange, and electrogenic uniport as in malate and citrate uptake in Leuconostoc oenos. In several of these processes additional H+ consumption occurs during metabolism leading to the generation of a pH gradient, internally alkaline. Lactic acid bacteria have also developed multidrug resistance systems. In Lactococcus lactis three toxin excretion systems have been characterized: cationic toxins can be excreted by a toxin/proton antiport system and by an ABC-transporter. This cationic ABC-transporter has surprisingly high structural and functional analogy with the human MDR1-(P-glycoprotein). For anions an ATP-driven ABC-like excretion systems exist.

ATP-Binding Cassette Transporters↗
PubMed2002

The extent to which ATP demand controls the glycolytic flux depends strongly on the organism and conditions for growth.

Using molecular genetics we have introduced uncoupled ATPase activity in two different bacterial species, Escherichia coli and Lactococcus lactis, and determined the elasticities of the growth rate and glycolytic flux towards the intracellular [ATP]/[ADP] ratio. During balanced growth in batch cultures of E. coli the ATP demand was found to have almost full control on the glycolytic flux (FCC=0.96) and the flux could be stimulated by 70%. In contrast to this, in L. lactis the control by ATP demand on the glycolytic flux was close to zero. However, when we used non-growing cells of L. lactis (which have a low glycolytic flux) the ATP demand had a high flux control and the flux could be stimulated more than two fold. We suggest that the extent to which ATP demand controls the glycolytic flux depends on how much excess capacity of glycolysis is present in the cells.

Adenosine Diphosphate↗
PubMed2003

Pediocin production by recombinant lactic acid bacteria.

Production of the anti-listerial bacteriocin, pediocin, by lactic acid bacteria (LAB) transformed with the cloning vector pPC418 (Ped+, 9.1 kb) was influenced by composition of media and incubation temperature. Maximum pediocin production, tested against Listeria innocua, by electrotransformants of Lactococcus lactis ssp. lactis was measured in tryptone/lactose/yeast extract medium after 24 h growth at 30 degrees C, while incubation at 40 degrees C was optimum for Ped+ transformants of Streptococcus thermophilus and Enterococcus faecalis. The amount of pediocin produced by S. thermophilus in skim milk and cheese whey supplemented with 0.5% yeast extract was estimated as 51,000 units ml(-1) and 25,000 units ml(-1), respectively. Pediocin production remained essentially unchanged in reconstituted skim milk or whey media diluted up to 10-fold. The results demonstrate the capacity of recombinant strains of LAB to produce pediocin in a variety of growth media including skim milk and inexpensive cheese whey-based media, requiring minimum nutritional supplementation.

Animals↗
PubMed2003

Lactic acid production using two food processing wastes, canned pineapple syrup and grape invertase, as substrate and enzyme.

Canned pineapple syrup, a food processing waste, was utilized as a substrate for lactic acid production by Lactococcus lactis. To improve the utilization of sucrose from the syrup, grape invertase from grape juice derived from wine production was used for sucrose hydrolysis. The highest lactic acid concentrations achieved were 20 and 92 g l-1 from 20 and 100 g total sugars l-1, respectively, without a lag period for sucrose consumption.

Ananas↗
PubMed2003

Lactic acid bacteria: inhibition of angiotensin converting enzyme in vitro and in vivo.

A total of 26 strains of wild-type lactic acid bacteria, mainly belonging to Lactococcus lactis and Lactobacillus helveticus, were assayed in vitro for their ability to produce a milk fermentate with inhibitory activity towards angiotensin converting enzyme (ACE). It was clear that the test strains in this study, in general, produce inhibitory substances in varying amounts. Using a spectrophotometric assay based on amino group derivatization with ortho-phthaldialdehyde as a measure of relative peptide content, it was shown that there is a significant correlation between peptide formation and ACE inhibition, indicating that peptide measurement constitutes a convenient selection method. The effect of active fermentates on in vivo ACE activity was demonstrated in normotensive rats. The pressor effect of angiotensin I (0.3 microg/kg) upon intravenous injection was significantly lower when rats were pre-fed with milks fermented using two strains of Lactobacillus helveticus. An increased response to bradykinin (10 microg/kg, intravenously injected) was observed using one of these fermented milks. It is concluded that Lactobacillus helveticus produces substances which in vivo can give rise to an inhibition of ACE. The inhibition in vivo was low compared to what can be achieved with classical ACE inhibitors. The clinical relevance of this finding is discussed. This work is the first in which an effect of fermented milk on ACE in vivo has been demonstrated, measured as decreased ability to convert angiotensin I to angiotensin II.

Angiotensin I↗
PubMed2003

Application of statistically-based experimental designs for the optimization of nisin production from whey.

Statistically-based experimental designs were applied for the optimization of nisin production by Lactococcus lactis in a whey-based medium. Yeast extract, KH2PO4, and MgSO4 were identified to have significant effects on nisin biosynthesis by a Plackett-Burman design. These three significant factors were subsequently optimized using central composite design, and the optimal conditions were determined to be 12.067 g l(-1) for yeast extract, 0.569 g l(-1) for KH2PO4, and 0.572 g l(-1) for MgSO4. The validity of the optimal conditions was verified by a separate experiment.

Animals↗
PubMed2003

L-Lactic acid production from raw cassava starch in a circulating loop bioreactor with cells immobilized in loofa (Luffa cylindrica).

L-Lactic acid was produced from raw cassava starch, by simultaneous enzyme production, starch saccharification and fermentation in a circulating loop bioreactor with Aspergillus awamori and Lactococcus lactis spp. lactis immobilized in loofa sponge. A. awamori was immobilized directly in cylindrical loofa sponge while the L. lactis was immobilized in a loofa sponge alginate gel cube. In the loofa sponge alginate gel cube, the sponge serves as skeletal support for the gel with the cells. The alginate gel formed a hard outer layer covering the soft porous gel inside. By controlling the rate and frequency of broth circulation between the riser and downcomer columns, the riser could be maintained under aerobic condition while the downcomer was under anaerobic condition. Repeated fed-batch L-lactic acid production was performed for more than 400 h and the average lactic acid yield and productivity from raw cassava starch were 0.76 g lactic acid g(-1) starch and 1.6 g lactic acid l(-1) h(-1), respectively.

Aspergillus↗
PubMed2003

Strong associations between gene function and codon usage.

The association between codon usage and gene function was analyzed in the complete genomes of Eschericia coli, Bacillus subtilis, Lactococcus lactis and Campylobacter jejuni, using the functional annotation provided by NCBI. Two distinctly different ways of quantifying codon usage were used in the analysis. By using contingency tables it was found that for most amino acids a highly significant association with gene function exists for all species, indicating that codon usage at the level of individual amino acids is generally closely coordinated with gene function. By computing the effective number of codons in the annotated genes and comparing the median values in groups of different gene functions it was shown for all species that codon bias gene by gene also differs.

Amino Acids↗
PubMed2000

Retrotransposition of a bacterial group II intron.

Self-splicing group II introns may be the evolutionary progenitors of eukaryotic spliceosomal introns, but the route by which they invade new chromosomal sites is unknown. To address the mechanism by which group II introns are disseminated, we have studied the bacterial L1.LtrB intron from Lactococcus lactis. The protein product of this intron, LtrA, possesses maturase, reverse transcriptase and endonuclease enzymatic activities. Together with the intron, LtrA forms a ribonucleoprotein (RNP) complex which mediates a process known as retrohoming. In retrohoming, the intron reverse splices into a cognate intronless DNA site. Integration of a DNA copy of the intron is recombinase independent but requires all three activities of LtrA. Here we report the first experimental demonstration of a group II intron invading ectopic chromosomal sites, which occurs by a distinct retrotransposition mechanism. This retrotransposition process is endonuclease-independent and recombinase-dependent, and is likely to involve reverse splicing of the intron RNA into cellular RNA targets. These retrotranspositions suggest a mechanism by which splicesomal introns may have become widely dispersed.

Bacterial Proteins↗
PubMed2003

An ABC transporter with a secondary-active multidrug translocator domain.

Multidrug resistance, by which cells become resistant to multiple unrelated pharmaceuticals, is due to the extrusion of drugs from the cell's interior by active transporters such as the human multidrug resistance P-glycoprotein. Two major classes of transporters mediate this extrusion. Primary-active transporters are dependent on ATP hydrolysis, whereas secondary-active transporters are driven by electrochemical ion gradients that exist across the plasma membrane. The ATP-binding cassette (ABC) transporter LmrA is a primary drug transporter in Lactococcus lactis that can functionally substitute for P-glycoprotein in lung fibroblast cells. Here we have engineered a truncated LmrA protein that lacks the ATP-binding domain. Surprisingly, this truncated protein mediates a proton-ethidium symport reaction without the requirement for ATP. In other words, it functions as a secondary-active multidrug uptake system. These findings suggest that the evolutionary precursor of LmrA was a secondary-active substrate translocator that acquired an ATP-binding domain to enable primary-active multidrug efflux in L. lactis.

ATP-Binding Cassette Transporters↗
PubMed1996

Development of an expression strategy using a lytic phage to trigger explosive plasmid amplification and gene expression.

A novel plasmid-based expression strategy, exploiting two features of lytic bacteriophages, was developed in Lactococcus lactis. Components of this system include a phage origin of replication and phage expression signals, which were induced to high efficiency upon phage infection of the host. Phage-specific expression signals were cloned from phi 31 in a promoter-screening strategy using the lacZ gene from Streptococcus thermophilus. One clone exhibited a significant induction in beta-galactosidase production and concomitant increase in lacZ mRNA during the phi 31 infection cycle of the host. Molecular characterization of the cloned insert revealed 888 bp positioned near the phi 31 cos site. Primer extension analysis showed that transcription was induced approximately 20 min following phi 31 infection at four points, apparently organized in two sets of tandem promoters on the cloned phage insert. One of these middle phage promoters also showed a basal level of activity prior to phage infection. The phi 31 promoter lacZ cassette was cloned into a low-copy-number vector plasmid containing the phi 31 origin of replication (ori31) and the resulting low-copy-number plasmid exhibited negligible beta-galactosidase production in L. lactis. However, > 2,000 units were detected following a deliberate infection with phi 31. A control expression plasmid without ori31 could only be induced to 85 units. The combination of these phage-inducible expression signals together with ori31 functioned synergistically to drive rapid and high efficiency expression of a heterologous gene in L. lactis.

Amino Acid Sequence↗
PubMed1997

Engineering pathways for malate degradation in Saccharomyces cerevisiae.

Deacidification of grape musts is crucial for the production of well-balanced wines, especially in colder regions of the world. The major acids in wine are tartaric and malic acid. Saccharomyces cerevisiae cannot degrade malic acid efficiently due to the lack of a malate transporter and the low substrate affinity of its malic enzyme. We have introduced efficient pathways for malate degradation in S. cerevisiae by cloning and expressing the Schizosaccharomyces pombe malate permease (mae1) gene with either the S. pombe malic enzyme (mae2) or Lactococcus lactis malolactic (mleS) gene in this yeast. Under aerobic conditions, the recombinant strain expressing the mae1 and mae2 genes efficiently degraded 8 g/L of malate in a glycerol-ethanol medium within 7 days. The recombinant malolactic strain of S. cerevisiae (mae1 and mleS genes) fermented 4.5 g/L of malate in a synthetic grape must within 4 days.

Bacterial Proteins↗
PubMed1994

A novel approach for high level production of a recombinant human parathyroid hormone fragment in Escherichia coli.

We describe a novel approach to the production in E. coli of a peptide fragment derived from the human parathyroid hormone (hPTH). The first 38 amino acids of hPTH were fused at the amino terminus to a derivative of the bacteriophage T4-encoded gp55 protein, and were expressed in the E. coli cytoplasm in inclusion bodies at levels exceeding 50% of the total cell protein. Solubilization and subsequent incubation of the inclusion bodies in dilute hydrochloric acid facilitated the cleavage of an acid-labile aspartyl-prolyl peptide bond engineered into the fusion protein, thus releasing the hormone fragment directly from the inclusion body preparation. The amino-terminal prolyl-prolyl dipeptide-extension was subsequently removed by treatment with Lactococcus lactis dipeptidyl peptidase IV which was overexpressed in E. coli and purified to near homogeneity from the cytosol of the recombinant bacteria. In pilot-scale fermentations, more than 80 mg of pure hPTH(1-38) were isolated per liter of bacterial culture, with an overall yield of 35%. This process is suitable for scale-up, is cost effective, and by employing recombinant dipeptidyl peptidase IV, should be widely and directly applicable to the manufacturing of peptides of pharmaceutical interest.

Amino Acid Sequence↗
PubMed1997

Design of thermolabile bacteriophage repressor mutants by comparative molecular modeling.

Comparative molecular modeling was performed with repressor protein Rro of the temperate Lactococcus lactis bacteriophage r1t using the known 3D-structures of related repressors in order to obtain thermolabile derivatives of Rro. Rro residues presumed to stabilize a nonhomologous but structurally conserved hydrophobic pocket, which was shown to be important for thermostability of the Escherichia coli bacteriophage lambda repressor CI, were randomized. Of the derivatives that exhibited various temperature-sensitive phenotypes, one was shown to hold promise for both fundamental and industrial applications that require the controlled production of (heterologous) proteins in L. lactis.

Amino Acid Sequence↗