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9 recordsLinked to original sources
PubMed1979

Preparation of high-fructose syrup from the tubers of the Jerusalem artichoke (Helianthus tuberosus L.

Fructose has recently received much attention due to renewed interest in natural sweeteners. In addition, fructose has some advantages to sucrose in sweetness, solubility, viscosity, and dental health characteristics. Fructose is deposited as storage fructans of the inulin (beta-1,2) type in tubers and rhizomes of the Compositae family. The utilization of the Jerusalem artichoke (Helianthus tuberosus) tuber as a source of fructose syrup is discussed. This plant has the potential to produce more sugar per acre than corn or sugar beets. In addition, the artichoke has higher frost resistance and lower heat unit requirements than corn and is somewhat more tolerant to low moisture conditions than sugar beets. A high quality fructose syrup can be produced from artichoke tubers. The extraction step was found to be particularly important since development of adverse colors and flavors must be prevented. The fructans may be acid or enzyme hydrolyzed but the latter method gave a higher quality syrup. Ion-exchange resins and activated charcoal were effective in removing coloring and flavoring materials, and also reduced other noncarbohydrate constituents. Since the enzymatic hydrolysis of the fructans is an attractive alternative to acid hydrolysis, a process was developed for producing and purifying a special beta-fructofuranosidase (inulase) from Saccharomyces fragilis. Inulase has a much higher specificity for fructans than commerically available beta-fructofuranosidase (invertase).

Carbohydrates↗
PubMed1977

Role of epitope density in the induction of immunity and tolerance with thymus-independent antigens. IV. Selective tolerance and IgE response by DNP-levan conjugates.

Tolerance induction of IgE antibody-forming cells by dinitrophenylated levan (DNP-LE) conjugates was investigated in CBA mice. Antibody production was measured by passive coutaneous anaphylaxis on rat skin. Specific antibody neutralization was obtained with conjugates of different substitution degrees. Specific inhibition of IgE antibody production was obtained only with highly substituted conjugates. However, the epitope density required for inducing tolerance to antibody synthesis of the IgE class was lower than for other classes of immunoglobulins. The tolerance induced by DNP-LE was shown to affect only the anti-DNP B cells of IgE class without T cell participation. These results demonstrate that B cell precursors of all Ig classes are susceptible to tolerance induction and not to triggering by T-independent antigens.

Animals↗
PubMed1979

A novel biological function of macrophages associated with antigen discrimination properties.

The ability of fresh or cultured subpopulation of adherent peritoneal exudate cells to perform discrete biological functions commonly associated with macrophages, namely antibody dependent cytotoxicity (ADCC) and phagocytosis, has been compared with the ability of the same cells to present TNP coupled to carbohydrate or protein carriers for a subsequent antibody response, or semi-allogeneic cells for T cell cytotoxic responses, in tissue culture. Data are presented to show that ADCC reactivity rapidly disappears on cultures of peritoneal cells, though phagocytic activity is more persistent throughout the 14 days of culture. When ADCC activity reappeared it was no longer restricted to those fractions active initially. Antigen handling of different TNP-protein conjugates was pronounced throughout the culture period and was not easily explained in terms of the ADCC/phagocytic activity of the macrophage subpopulation concerned. In contrast, however, antigen handling of carbohydrate antigens for presentation to T or B lymphocytes by the different macrophage populations varied during the culture period in fashions which were in some degree correlated with the phagocytic activity of the various cells but were also a function of the antigen under consideration. These data are interpreted in terms of a novel role for the macrophage in discrimination of carbohydrate antigens for presentation to lymphocytes.

Animals↗
PubMed1978

Degradation of levan by Actinomyces viscosus.

Actinomyces viscosus ATCC 15987 was examined for its ability to hydrolyze its own levan. Washed whole cells and an ammonium sulfate fraction from cell-free culture fluids were shown to possess levan hydrolase activity. Analyses of reaction mixtures by gel filtration and thin-layer chromatography demonstrated that the product of levan hydrolysis was free fructose. The cell-associated and extracellular enzyme preparations also hydrolyzed inulin and the levans synthesized by Aerobacter levanicum and Bacillus subtilis. Growth of A. viscosus in media supplemented with 0.1% A. viscosus levan resulted in a 33-fold increase and a 7-fold increase in the specific activities of the respective extracellular and cell-associated enzymes when compared with those from 55 mM glucose cultures. Growth in the presence of 29.2 mM sucrose resulted in a 28-fold increase and a 5-fold increase in the specific activities of the respective enzymes when compared with those from the glucose cultures. The extracellular enzyme exhibited high activity over a wide pH range, with 87 and 89% of its pH 6.0 optimum activity at pH 5.0 and 7.0, respectively. The cell-associated enzyme also exhibited optimum activity at pH 6.0, but this was decreased to 10 and 20% at pH 5.0 and 7.0, respectively. Analysis for the presence of extracellular levan during growth of A. viscosus in sucrose broths demonstrated that peak levan concentrations occurred during the mid-exponential to late-exponential phase of growth followed by a rapid decline in extracellular levan as a result of levan hydrolase activity.

Actinomyces↗
PubMed2026

Periplasmic SacB as a robust counter-selection tool for genome engineering in the polyploid bacterium Zymomonas mobilis.

UNLABELLED: The alpha-proteobacterium Zymomonas mobilis exhibits exceptional ethanologenic physiology, which makes it a traditional alcoholic beverage producer and a promising chassis for biofuel production. Although genetic tools for this organism have expanded in recent years, a fundamental aspect of its chromosome organization remains to be understood. In particular, Z. mobilis has been suggested to exhibit polyploidy, but this feature is not fully confirmed because of discrepancies among studies reporting the copy number of chromosomes. Here, we tagged the chromosome-partitioning protein ParB with a fluorescent marker to visualize its cellular localization and estimate chromosome copy number in individual cells. Imaging showed that Z. mobilis exhibits several distinctive ParB foci throughout the cytoplasm and an accumulated focus at the pole, indicating that a single Z. mobilis cell contains >5 copies of the chromosome at the oriC regions. We then sought to establish an efficient counter-selection system, which is crucial for engineering multiple copies of the chromosome. We assessed the efficacy of levan-sucrase (SacB) toxicity in Z. mobilis. We found that, despite Z. mobilis secreting a native extracellular sucrase SacB, heterologous periplasmically localized Bacillus subtilis SacB rendered Z. mobilis cells sensitive to sucrose. We successfully used this effect for counter-selection when deleting and inserting targeted DNA sequences into the Z. mobilis genome. Together, this work provides important insights and tools for advancing Z. mobilis genetics and its biotechnological applications. IMPORTANCE: Zymomonas mobilis is a promising industrial bacterium with the capacity to convert sugars into ethanol at nearly maximum theoretical yield. With its expanding use in industrial applications, it is crucial to clarify if individual Z. mobilis cells carry multiple copies of the chromosome, as this has important implications for genome engineering. Two previous studies have used quantitative PCR to address this question, but their reported chromosome copy numbers varied widely from 20 to 100. Here, we used a cell biological approach to estimate the copy number and confirmed that a single Z. mobilis cell possesses multiple copies. In addition, we show that a SacB-based counter-selection works in Z. mobilis, enabling efficient and complete mutation of all chromosome copies.

Zymomonas↗
PubMed1979

The use of hapten-polysaccharide conjugates for the induction of B-cell tolerance involving IgE responses. III. Specific tolerance induced by sulphonamide-substituted levan in the guinea pig.

Inbred strain 2 and (strain 2 x strain 13)F1 guinea pigs were made allergic by intraperitoneal injections of sulphonamide-chicken gamma-globulin (CGG) conjugates. Two sulphonamides were used: 4-sulphanilamide benzoic acid (4-SABA) and sulphamethoxazole (SMX). 4-SABA was coupled to CGG through its carboxylic group and SMX was coupled following diazotization of its sulphanilamide group. The anti-4-SABA and anti-SMX reaginic antibodies formed did not show any cross-reactivity with each other. Injection of 4-SABA coupled to native levan effectively suppressed the allergic responses of these guinea pigs when given either prior to or after immunization with 4-SABA-CGG. This treatment is specific as it did not affect anti-SMX or anti-CGG reaginic responses. Guinea pigs seem more sensitive to the regime used for tolerance induction than correspondingly sensitized mice in that less tolerogen is required on a body weight basis.

Animals↗
PubMed1977

Effects of prolonged administration of high molecular levan on arterial blood gases, oxygen transport and acid base balance in rabbits.

The effect of daily intraperitoneal injections of 100 mg of high molecular levan for 4-6 weeks on a number of physiological parameters was studied in rabbits. The parameters studied included whole blood pH, blood gases and acid-base balance. Control rabbits were similarly treated with physiological saline. In five rabbits T-50 was determined after levan treatment. None of the studied parameters was significantly affected by the levan treatment.

Acid-Base Equilibrium↗
PubMed1979

Idiotypic specificities and cross-reactivities of rabbit antibodies to human antidextran.

Idiotypic antibodies were prepared by immunizing two groups of rabbits with dextran-antidextran specific precipitates and purified antidextran obtained subsequently from the same human donor. Half of the animals were made tolerant to pooled human IgG. Tests showed that sera from tolerant rabbits reacted better with the antidextran preparation used to immunize the other group of animals than with the antidextran that formed part of their immunogen. Non-tolerant animals did not recognize this serological difference. Sera from animals immunized with the antidextran preparation donated later reacted better with this material irrespective of their tolerance to human IgG.

Animals↗