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Biomedical subjects

D F Day

Publications and source records attributed to D F Day.

At least 19 recordsLinked to original sources
PubMed2005

Isomaltooligosaccharide increases cecal Bifidobacterium population in young broiler chickens.

A newly developed compound derived by fermentation, isomaltooligosaccharide (IMO), was hypothesized to enrich cecal bifidobacterial populations and reduce colonization levels of Salmonella in the ceca of broiler chickens. Broiler starter diets were prepared with final IMO concentrations of 1% (wt/wt), 2% (wt/wt), and 4% (wt/wt) and a control diet without IMO supplementation. Chickens were divided into 4 groups and challenged with 10(8) cell of Salmonlella enterica ser. Typhimurium with 200 microg/mL nalidixic acid resistant (S. Typhimurium Nalr) after 7 d of placement. The experiment was done in 3 replications. IMO-supplemented diets resulted in significantly higher cecal bifidobacteria compared with the control diet (P < 0.05). However, there was no significant difference in bifidobacteria counts among the treatment groups. Chickens fed diets with 1% IMO had a significant 2-log reduction in the level of inoculated S. Typhimurium Nalr (P < 0.05) present in, the ceca compared with the control group, but no differences were found between the control group and the groups fed 2 or 4% IMO for S. Typhimurium Nalr. No differences in feed consumption, feed conversion, or feed efficiency compared with the control group were observed; however, the result showed a significant reduction in weight for birds fed 1% IMO diet compared with those fed the control diet.

Animal Nutritional Physiological Phenomena↗
PubMed2004

Efficacy of Leuconostoc mesenteroides (ATCC 13146) isomaltooligosaccharides as a poultry prebiotic.

The complex dietary carbohydrates, called prebiotics, have been used to control Salmonella and improve intestinal bacterial balance in broilers. Leuconostoc mesenteroides (ATCC 13146) isomaltooligosaccharides (IMO) stimulate growth of Bifidobacterium and Lactobacillus and are not used by Salmonella or Escherichia coli. We tested the efficacy of these IMO as a prebiotic. IMO, compared with fructooligosaccharides (FOS) as sole carbon source, promoted growth of chicken cecal isolates and Bifidobacterium. Cecal isolates and Salmonella typhimurium grown in mixed culture on IMO reduced the Salmonella population. Cecal isolates grown on IMO showed higher viable counts and faster growth than Salmonella, indicating a potential value for these oligomers for poultry intestinal microflora modification.

Animals↗
PubMed2002

Glucooligosaccharides from Leuconostoc mesenteroides B-742 (ATCC 13146): a potential prebiotic.

There is an emerging market for functional oligosaccharides for use in foods. Currently, technology for the production of oligosaccharides is limited to extraction from plant sources, acid or enzymatic hydrolysis of polysaccharides or synthesis by transglycosylation reactions. Oligosaccharides can also be produced using a Leuconostoc fermentation and restricting the polymer size by addition of maltose. Maltose limits the dextransucrase reaction, yielding high concentrations of alpha-glucooligosaccharides. Branched oligomers produced by this process were readily catabolized by bifidobacteria and lactobacilli but were not readily utilized by either Salmonella sp. or Escherichia coli, pointing toward their use in intestinal microflora modification.

Bifidobacterium↗
PubMed2001

The release of alginate lyase from growing Pseudomonas syringae pathovar phaseolicola.

Pseudomonas syringae pathovar phaseolicola, which produces alginate during stationary growth phase, displayed elevated extracellular alginate lyase activity during both mid-exponential and late-stationary growth phases of batch growth. Intracellular activity remained below 22% of the total activity during exponential growth, suggesting that alginate lyase has an extracellular function for this organism. Extracellular enzyme activity in continuous cultures, grown in either nutrient broth or glucose-simple salts medium, peaked at 60% of the washout rate, although nutrient broth-grown cultures displayed more than twice the activity per gram of cell mass. These results imply that growth rate, nutritional composition, or both initiate a release of alginate lyase from viable P. syringae pv. phaseolicola, which could modify its entrapping biofilm.

Plant Diseases↗
PubMed2000

Purification and partial characterization of a novel glucanhydrolase from Lipomyces starkeyi KSM 22 and its use for inhibition of insoluble glucan formation.

A novel glucanhydrolase from a mutant of Lipomyces starkeyi ATCC 74054 was purified. The single protein (100 kDa) showed either dextranolytic or amylolytic activity. We referred to the glucanhydrolase as a DXAMase. The DXAMase was produced in a starch medium and it was 3.75-fold more active for hydrolysis of the purified insoluble-glucan of Streptococcus mutans than Penicillium funiculosum dextranase. Aggregation of S. mutans cells with dextran and adherence to glass were eliminated by incubating with the DXAMase. The addition of DXAMase (0.1 IU/ml) to the mutansucrase reaction digest with sucrose reduced the formation of insoluble-glucan about 80%. Also the DXAMase (0.5 IU/ml) removed 80% of the pre-formed sucrose-dependent adherent film. These in vitro properties of L. starkeyi KSM 22 DXAMase are desirable for its application as a dental plaque control agent.

Dental Materials↗
PubMed1995

Isolation of a dextranase constitutive mutant of Lipomyces starkeyi and its use for the production of clinical size dextran.

A derepressed and partially constitutive mutant for dextranase of Lipomyces starkeyi was selected after ethyl methane sulphonate mutagenesis by zone clearance on blue dextran agar plates. The mutant produced dextranase when grown on glucose, fructose and sucrose as well as on dextran, and more enzyme was produced by the mutant than by the parental strain when grown on 1% dextran. The pH and temperature optima for the mutant dextranase were 5.5 and 55 degrees C, respectively. Dextranase produced on sucrose produced more isomaltose and less glucose after dextran hydrolysis than the equivalent enzyme produced on dextran. The clinical size dextran (average mol. wt of 75,000 +/- 25,000) yield of mixed culture fermentation with the mutant and Leuconostoc mesenteroides was 94% of the total dextran produced.

Dextranase↗
PubMed1995

Bioacetylation of seaweed alginate.

Seaweed alginate was acetylated by intact, resting cells of Pseudomonas syringae ATCC 19304. Maximum acetylation of this polymer occurred at a pH of 6.0 and a temperature of 25 deg C. Aeration and gluconic acid were required for an optimal reaction. A reactor which contained carbon-immobilized cells was constructed to continuously acetylate alginate. The maximal yield of acetylation was about 90%, and the half-life of this system was 6.5 days.

Journal Article↗
PubMed1994

A new process for the production of clinical dextran by mixed-culture fermentation of Lipomyces starkeyi and Leuconostoc mesenteroides.

A mixed-culture fermentation system was designed for the production of size-limited dextrans. This process was simpler and more economical than traditional methods. It required the establishment of microbial consortia of Lipomyces starkeyi ATCC 74054 and Leuconostoc mesenteroides ATCC 10830. Controlling initial conditions, growth, and enzyme production by both organisms controlled the product size. In this process, both strains were grown separately and then mixed. Dextran fermentation was then allowed to proceed. At the desired time (and molecular size), the fermentation was harvested. The optimum pH and temperature for production of clinical dextran (75,000 MW) were 5.2 (+/- 0.1) and 28 (+/- 0.5) degrees C, respectively. Varying the ratio of L. mesenteroides to L. starkeyi in the inoculum did not significantly affect either the final cell ratios or dextran production.

Biotechnology↗
PubMed1993

Increased susceptibility of Pseudomonas aeruginosa to ciprofloxacin in the presence of vancomycin.

Vancomycin in combination with ciprofloxacin exhibited synergy against 7 of 10 strains of Pseudomonas aeruginosa. MICs for the microbial strains used in this study ranged from 0.0325 to 3.0 micrograms/ml for ciprofloxacin and from 23.5 to > 188 micrograms/ml for vancomycin. Combinations of these antibiotics, tested in a checkerboard pattern, gave fractional inhibitory concentrations of 0.5 or less for 7 of the 10 strains tested.

Anti-Infective Agents↗
PubMed1988

Dextransucrase secretion in Leuconostoc mesenteroides depends on the presence of a transmembrane proton gradient.

The relationship between proton motive force and the secretion of dextransucrase in Leuconostoc mesenteroides was investigated. L. mesenteroides was able to maintain a constant proton motive force of -130 mV when grown in batch fermentors at pH values 5.8 to 7.0. The contribution of the membrane potential and the transmembrane pH gradient varied depending on the pH of the growth medium. The differential rate of dextransucrase secretion was relatively constant at 1,040 delta mU/delta mg (dry weight) when cells were grown at pH 6.0 to 6.7. Over this pH range, the internal pH was alkaline with respect to the external pH. When cells were grown at alkaline pH values, dextransucrase secretion was severely inhibited. This inhibition was accompanied by an inversion of the pH gradient as the internal pH became more acidic than the external pH. Addition of nigericin to cells at alkaline pH partially dissipated the inverted pH gradient and produced a fourfold stimulation of dextransucrase secretion. Treatment of cells with the lipophilic cation methyltriphenylphosphonium had no effect on the rate of dextransucrase secretion at pH 5.5 but inhibited secretion by 95% at pH 7.0. The reduced rate of secretion correlated with the dissipation of the proton motive force by this compound. Values of proton motive force greater than -90 mV were required for maximal rates of dextransucrase secretion. The results of this study indicate that dextransucrase secretion in L. mesenteroides is dependent on the presence of a proton gradient across the cytoplasmic membrane that is directed into the cell.

Cell Membrane↗
PubMed1987

Optimization of Protoplast Formation and Regeneration in Leuconostoc mesenteroides.

Conditions are reported for efficient protoplast formation and regeneration in four strains of Leuconostoc mesenteroides. Protoplasts were produced from each strain at frequencies greater than 99%, although the rate of their production was variable from strain to strain. Bovine serum albumin and Mg were required for maximal regeneration, while the presence of Ca was inhibitory. Regeneration frequencies of 16% could be obtained with strain ATCC 10830. This frequency was four- to eightfold higher than the frequencies of the other strains examined.

Journal Article↗
PubMed1984

The cell wall-associated inulinase of Kluyveromyces fragilis.

The yeast Kluyveromyces fragilis (ATCC 12424) was grown on a 2% inulin-1% yeast extract medium for 36 h and subsequently fixed with 0.5% glutaraldehyde. The glutaraldehyde treatment did not affect the beta-fructofuranosidase (inulinase, EC 3.2.1.7) activity of the cells but it did make the cells resistant to chemical and physical treatments that normally release beta-fructofuranosidase from untreated cells. The enzyme in the treated cells exhibited Km values for sucrose and raffinose identical to those obtained for the free enzyme. The cell wall of the treated cells exhibited the same diffusion properties for sucrose, raffinose, and inulin as those observed for untreated cells. The beta-fructofuranosidase was not bound covalently to the cell by the glutaraldehyde treatment. The results support the permeability barrier model for the enzyme retention in the yeast cell wall.

Ascomycota↗
PubMed1984

A simple inulin assay for renal clearance determination using an immobilized beta-fructofuranosidase.

Current hospital practice for testing renal function is to use the creatinine clearance test. Inulin clearance, an inherently more accurate procedure, currently is only carried out by specialized laboratories because there is not a simple biochemical assay for inulin, that is, an assay that could be carried out by any laboratory without special facilities. We have developed a simple enzymatic assay system for measuring inulin in plasma and urine. The procedure uses a beta-fructofuranosidase immobilized on Concanavalin A to convert inulin to fructose. Fructose is then measured by measuring the NADH----NAD conversion produced when fructose is converted to sorbitol by the enzyme sorbitol dehydrogenase. Kinetic parameters, binding capacities, and operating conditions for the immobilized beta-fructofuranosidase were determined as well as general operating parameters for the complete assay system. This system offers the potential for replacing the creatinine clearance test as the assay of choice for renal function.

Enzymes, Immobilized↗
PubMed1983

Purification and properties of the beta-fructofuranosidase from Kluyveromyces fragilis.

The beta-fructofuranosidase from Kluyveromyces fragilis was purified to one band on electrophoresis by 3 different methods. Two of the preparations were found to be impure by isoelectric focusing. This demonstrates the need for more than one criteria of homogeneity when purifying this enzyme. The enzyme was found to be a glycoprotein, stable at 50 degrees C, with a pH optimum of 4.5. The cations Hg2+, Ag+, Cu2+ and Cd2+ exhibited a marked inhibition of the enzyme. Competitive inhibition was observed with the fructose analog 2,5-anhydro-D-mannitol suggesting that the enzyme is inhibited by the furanose form of fructose.

Ascomycota↗
PubMed1983

Effects of cultural conditions on protease production by Aeromonas hydrophila.

Production of extracellular proteolytic activity by Aeromonas hydrophila was influenced by temperature, pH, and aeration. Conditions which produced maximal growth also resulted in maximal protease production. Enzyme production appeared to be modulated by an inducer catabolite repression system whereby NH4+ and glucose repressed enzyme production and complex nitrogen and nonglucose, carbon energy sources promoted it. Under nutritional stress, protease production was high, despite poor growth.

Aerobiosis↗
PubMed1982

Purification and Properties of beta-Glucosidase from Aspergillus terreus.

A beta-glucosidase (EC 3.2.1.21) from the fungus Aspergillus terreus was purified to homogeneity as indicated by disc acrylamide gel electrophoresis. Optimal activity was observed at pH 4.8 and 50 degrees C. The beta-glucosidase had K(m) values of 0.78 and 0.40 mM for p-nitrophenyl-beta-d-glucopyranoside and cellobiose, respectively. Glucose was a competitive inhibitor, with a K(i) of 3.5 mM when p-nitrophenyl-beta-d-glucopyranoside was used as the substrate. The specific activity of the enzyme was found to be 210 IU and 215 U per mg of protein on p-nitrophenyl-beta-d-glucopyranoside and cellobiose substrates, respectively. Cations, proteases, and enzyme inhibitors had little or no effect on the enzyme activity. The beta-glucosidase was found to be a glycoprotein containing 65% carbohydrate by weight. It had a Stokes radius of 5.9 nm and an approximate molecular weight of 275,000. The affinity and specific activity that the isolated beta-glucosidase exhibited for cellobiose compared favorably with the values obtained for beta-glucosidases from other organisms being studied for use in industrial cellulose saccharification.

Journal Article↗