Levan formation by Odontomyces viscosus

Immunochemical studies on levans from several strains of Actinomyces viscosus

High molecular-weight levans elaborated by 8 separate strains of Actinomyces viscosus were purified: the inteactions of these levans with concanavalin A and anti-fructan myeloma immunoglobulins UPC-10 and J606 were examined by the quantitative precipitin method. Oligosaccharides released from the levans by partial acid hydrolysis were separated by partition chromatography on paper and characterized in situ by selective spray reagents. The liberated oligomers were compared with oligomers of known structure released from levans of Aerobacter levanicum and Leuconostoc mesenteriodes B512 as well as with plant inulin. The fragmentation analysis indicated a structure for Actinomyces levans comprising chains of beta (2----6)-linked fructofuranosyl units joined through multiple (1,2,6)-linked fructosyl branch units.

Microbial levan

Levans are natural polymers of the sugar fructose found in many plants and microbial products. Like dextrans, they are formed as an undesirable by-product of sugar juice processing. On the other hand, levans, which can only be produced from sucrose, have potential industrial applications as thickeners and encapsulating agents and could provide additional, valuable products from sugarcane juice. A strain of B. polymyxa (NRRL B-18475) produced a high yield of polysaccharide when grown on sucrose solution. Hydrolysis and subsequent analyses showed the product to consist entirely of D-fructose. 13C-NMR and methylation analyses indicated the products to be a beta(2----6)-linked polymer of fructose, with 12% branching. The polysaccharide has a Mr of approximately 2 million and is readily soluble in water. Levan has not been utilized, but if developed, could be useful in food and other industrial applications.

Purification and characterization of levanase from Actinomyces viscosus ATCC 19246

The extracellular levanase of Actinomyces viscosus ATCC 19246 was purified about 3,701-fold in 11% yield from the bacterial culture supernatant by means of ammonium sulfate precipitation, followed by DE52 column chromatography, Sephadex G-100 gel filtration, hydroxylapatite column chromatography, and Bio-Gel A 1.5m gel filtration. The molecular weight of the enzyme was estimated to be 89,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme was optimally reactive at pH 6.0 and at 45 degrees C. The activity was inhibited by MnCl2, BaCl2, FeCl3, ZnCl2, HgCl2, and EDTA at a final concentration of 1 mM. The inhibition by EDTA was recovered by adding CaCl2 or MgCl2. The enzyme specifically hydrolyzed levan, but not sucrose, raffinose, melezitose, inulin, and dextran. These results indicate that the purified enzyme is specific for fructan (i.e., levan), which mainly consists of beta-(2,6) linkages.

Isolation and properties of levanase from Streptococcus salivarius KTA-19

Fructan-hydrolyzing enzyme from Streptococcus salivarius KTA-19 isolated from human dental plaque was investigated. The enzyme was purified by ammonium sulfate precipitation, acetone fractionation, and column chromatography on Bio-Gel and DEAE-cellulose. The purified enzyme showed a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and isoelectric focusing. Its molecular weight was 100,000 as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The enzyme exhibited an optimum pH of 6.5 and decreased its activity from pH 6.0 and especially below pH 5.5. The optimum temperature was 40 to 50 degrees C, and enzyme activity was reduced by 90% at 55 degrees C. Enzyme activity was markedly inhibited by Hg2+, Ag+, Cu2+, and p-chloromercuribenzoate at a concentration of 10(-3) M, but not by other metal ions or chemical effectors. Fructose was the only by-product of the enzyme action on levan. These results indicated that the levanase of S. salivarius KTA-19 is an exo-beta-(2,6)-fructofuranosidase.

Chemical characterization of extracellular polysaccharides produced by Actinomyces viscosus T14V and T14Av

The human isolates Actinomyces viscosus T14V and T14Av produced extracellular polysaccharides in the absence of sucrose. In contrast to strain T14V, strain T14Av produced abundant viscous slime polysaccharide in the culture supernatant fluids when grown in a chemically defined medium containing glucose. After resolution of the T14Av polysaccharides into seven fractions, it was demonstrated that two of these exhibited viscous properties and lacked methylpentose and muramic acid. The major slime polysaccharide purified by gel filtration and ion-exchange column chromatography contained 39% (moles percent carbohydrate) galactose, 37% N-acetylglucosamine, 19% glucose, and 5% mannose. Only trace amounts of protein and phosphorus were detected in this preparation. On the other hand, strain T14V produced negligible slime polysaccharide under the same culture conditions. The major extracellular polysaccharide fraction from this strain contained methylpentoses, hexoses, hexosamines, muramic acid, protein, and phosphorus, suggesting that this fraction might be derived from the cell wall.

Minimum nutritional requirements for cellular growth and extracellular slime polysaccharide production by the human dental plaque bacterial mutant Actinomyces viscosus T14Av

The requirements were examined in chemically-defined media. Magnesium sulphate, potassium phosphate and adenine were essential for cellular growth and sodium bicarbonate and inositol further stimulated growth. The addition of sodium phosphate to this medium stimulated both cellular growth and slime production. In contrast, ammonium sulphate inhibited slime production. Biotin and thiamine stimulated cellular growth and nicotinic acid was essential for slime production. Glutamine, alanine and cystine were essential for cellular growth. A minimal medium which supported both good cellular growth and slime production for strain T14Av contained adenine, sodium bicarbonate, MgSO4, inositol, glucose, KH2PO4, Na2HPO4, biotin, thiamine, nicotinic acid, arginine, glutamine, alanine and cystine.

Extracellular beta-D-fructofuranosidase elaborated by Streptococcus salivarius strain 51: preparation, and mode of action on a levan and on homologues of inulobiose

Streptococcus salivarius strain 51 produces an extracellular beta-D-fructofuranosidase when grown in a levan-containing medium. The enzyme hydrolyses levan, and inulo-biose, -tetraose, -pentaose, and -hexaose, but has negligible effects on inulin, inulotriose, and inuloheptaose. The branching in S. salivarius strain 51 levan is through a single (2 yields 1)-beta-D linkage.

Degradation of sucrose by whole cells and plaque of Actinomyces naeslundii

Whole cells of Actinomyces naeslundii ATCC 12104, either in a dispersed form or in the form of plaque, enzymatically degraded sucrose to glucose and fructose. Washed whole cells expressed beta-fructofuranosidase specificity and hydrolyzed sucrose to essentially equimolar quantities of glucose and fructose. The cells readily hydrolyzed sucrose, raffinose, and Actinomyces viscosus or Aerobacter levanicum levan, but did not degrade melezitose, maltose, alpha-methyl-d-glucoside, melibiose, glucose-1-phosphate, or dextran T-500. Sucrose degradation occurred at a temperature optimum of 37 to 45 C and at a pH optimum of 5.7 to 6.0. The K(m) for sucrose was 0.05 M. Sucrose or raffinose in the growth medium resulted in cells with a specific activity that was fivefold greater than that of cells grown in medium supplemented with either glucose, fructose, maltose, lactose, or glucose and fructose, or grown in unsupplemented medium. Addition of sucrose to log-phase cells growing in glucose also increased the specific activity. Degradation of sucrose by whole cells in the form of plaque also occurred, but 6% less free fructose than free glucose was recovered. Sucrose-dependent synthesis of extracellular levan or glucan by whole cells or plaque could not be demonstrated. The ability of A. naeslundii to degrade sucrose and levan may be related to the pathogenic potential of this bacterium in plaque-associated oral diseases.

Extracellular polysaccharides of Actinomyces viscosus

Polysaccharide(s) have been isolated from supernatants of broth cultures of Actinomyces viscosus, strain T6. The organism produces significant quantities (2 mg/mg of cell [dry weight], 108 mg/liter) of this polysaccharide in the absence of sucrose. Chemical analysis indicated that N-acetylglucosamine (62%) was the major component; galactose (7%), glucose (4%), uronic acid (3%), and smaller amounts of glycerol, rhamnose, arabinose, and xylose were also present. The polysaccharide(s) is only slightly soluble in aqueous solutions. Although further purification of the polysaccharides will be necessary before definitive chemical and structural studies, the formation of extracellular polysaccharides is significant because it offers a possible explanation for plaque formation by these organisms.