Levan hydrolyzed

However, some carbohydrates with a terminal D-fructofuranose residue are not suitable substrates for levan formation, e. g., methyl /3-d-fructofuranoside and inulin,64 even in the presence of enzymes98 which hydrolyze these substrates. 

Two methylations of levan by means of dimethyl sulfate and potassium hydroxide (not sodium hydroxide) followed by one inethylation with methyl iodide and silver oxide yielded trimethyllevan in 88% yield. This was purified by solvent fractionation over-all yield 75%, m. p. 145-146°, OCHs 45.9%. Trimethyllevan, hydrolyzed by heating at 95° for twenty-four hours with a dilute solution of sulfuric acid gave a 98.5% yield of a crystalline trimethyl-D-fructose. The trimethyl-D-fructose was proved940 to be 1,3,4-trimethyl-D-fructofuranose since oxidation with nitric acid gave a 97% yield of a dimethyl-2-keto-D-gluco-saccharic acid which was identified as the crystalline diamide (95% yield). 

The specificity of levansucrase98 is dependent not only on the d-fructoside but also on the aldoside residue of the substrate. Neither inulin nor methyl D-fructofuranoside was hydrolyzed by levansucrase, and even when these two substrates were hydrolyzed by inulase (prepared from inulin-fermenting Torula yeast) or by yeast invertase respectively, no levan formation occurred with levansucrase. However, neither methyl D-fructofuranoside nor inulin inhibited levan formation from sucrose by levansucrase. No levan was formed from potassium D-glucose... 

Indirect evidence of the reversal of enzymic synthesis of levan has recently been obtained.10Ba Enzyme preparations from B. subtilis were shown to contain an enzyme capable of hydrolyzing levan (in addition to the levan-synthesizing enzyme) in a system composed of D-glucose, levan, yeast invertase (to hydrolyze sucrose formed) and the B. subtilis enzyme preparation. 

Polymers of D-fructose are important carbohydrate reserves in a number of plants. Inulins and levans are two major types that differ in structure. D-Fructans require only relatively mild conditions for their hydrolysis, for example, levan was qualitatively hydrolyzed by hot, dilute, aqueous oxalic acid. Permethylated fructans could be hydrolyzed with 2 M CF3CO2H for 30 min at 60°. Fructan oligosaccharides were hydrolyzed in dilute sulfuric acid (pH 2) at 70 (see Ref. 53) or 95° (0.1 M). D-Fructans from timothy haplocorm (where they comprise 63% of the water-soluble carbohydrates) could be hydrolyzed with 0.01 M hydrochloric acid at 98°. 

In water, inulin undergoes reversion from a more soluble to a less soluble form, in the manner of retrograding starch (Whistler and Smart, 1953) it is slightly soluble in organic solvents. Fructans are easily hydrolyzed by acid. Levan is the branched isomer of inulin. 

The solution properties of native S. salivarius levan, including fractionated moieties, were reported in earlier papers by Stivala and co-workers (11, 20, 21, 22, 2. A number of physicochemical parameters of native S. subtvlis levan, Including the products from mild acid hydrolyses of molecular weights ranging from 100 X 10 to a low of several thousands, were reported by Dedonder and Sllcewlcz (2k). This paper will review our earlier work on the solution properties of S. saZivco ius levan and extend our recent work (25) on the solution properties of fractionated moieties of the acid hydrolyzed levan. 

Hydrolyses Native levan was hydrolyzed at pH 2 at 35°C according to procedures described In earlier papers (18, 25). 

II. Solution Parameters of Hydrolyzed Levan. The hydrolysis of native levan effected a reduction in from 43 x 10 to... 

X 10 dal tons. The fractionation of the partially hydrolyzed levan yielded 32 fractions varying in from 8 x I06 down to 10 (25, 27). Double logarithmic plots of (nl vs. and S vs. each yielded two linear segments intersecting at n- 10. The exponents of the former were 0.05 and 0.67 for in the range of 8 X 10 to 2 X 1o5 and 9 x 10 to 10, respectively, whereas those of the latter were 0.67 and 0.43, respectively. Examination of the values of these exponents suggested that the levan hydrolysates of > 105 are best characterized by spheres and those of 105 exhibit random coil behavior (25, 27). Cal-... 

Figure 2. Log-log plot of intrinsic viscosity va. M for hydrolyzed levan fractions...

It is noteworthy to mention, in support of the observation in Figure 2 on S. salivarius levan, the work of Dedonder and Slizewicz (24). These investigators examined the fractions of the partially acid hydrolyzed B. subtilis levan. They reported that a significant change in the structure of this levan occurs following hydrolysis. 

Zweig, J.E. "The Physico-Chemical Characterization of Acid Hydrolyzed S. sativarius Levan" 1977 Ph.D. Dissertation Stevens Institute of Technology, Hoboken, N.J. 

The elucidation of a levan polysaccharide produced by a novel halophilic isolate from soil samples taken from Camalti Saltern area in Turkey, Halomonas smyrniensis was achieved thanks to the glycosyl analysis. In particular, the microbial EPS was hydrolyzed with trifluoroacetic acid (0.5M TFA at temperature of 120°C for 1.5h) and subsequently analyzed by HPAE-PAD (High-Performance Anion-Exchange Chromatography Pulsed Amperometric Detection), a high-performance anion-exchange... 

Levanpolyase. Levans are hydrolyzed by specific bacterial enzymes to ohgofructosides that are further metabolized by conventional fructo-sidases. These latter will not attack intact levans, however. 

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