Frederick R. Dintzis

Studies on dilute solutions and dispersion of the polysaccharide from Xanthomonas campestris NRRL B-1459☆

Abstract Some properties of the extracellular polysaccharide produced by the bacterium Xanthomonas campestris NRRL B-1459 were measured in partially purified culture fluids and in liquid systems prepared from thoroughly purified and lyophilized material. High intrinsic viscosities resulted from dispersions and solutions of polysaccharide B-1459 in 0.01 m ammonium acetate and 4 m urea. Heating a dispersion of B-1459 in 4 m urea yielded a true macromolecular solution in which the polysaccharide had an apparent molecular weight of approximately 2 × 10 6 . Lightscattering measurements on culture fluids of B-1459 made 4 m in urea gave molecular weights of 13 × 10 6 and 50 × 10 6 . Various solution-properties and factors that affect the viscosity of dispersions prepared from lyophilized polysaccharide are presented.

High-performance liquid chromatographic method for the determination of phytate

Abstract An improved method for the determination of phytate ( myo -inositol 1,2,3,5 4,6 hexakis (dihydrogen phosphate)) in plants is described. Phytate is extracted with 0.5 n HCl, purified and concentrated on an AG 1-X8 anion-exchange resin, taken to dryness in a vacuum desiccator, and analyzed by reverse-phase liquid chromatography on a μBondapak C 18 column. The refractive index peak due to phytate is well separated from a minor salt peak, and the area under the peak is linearly proportional to the phytate concentration over a wide range. Unlike most conventional methods involving precipitation by FeCl 3 , the simpler and more reliable high-performance liquid chromatographic (hplc) assay avoids the numerous assumptions inherent in the iron precipitation, and accuracy is independent of the phytate content. As little as 0.003% phytate in plants may be quantitated with a coefficient of variation of less than 5%. When several cereal brans are analyzed by both the present method and a colorimetric method, excellent agreement is obtained between the values for phytate content at concentrations greater than 0.2%; lower concentrations can be detected only by the hplc method.

Properties of amylose-iodine complexes prepared in the presence of excess iodine

Abstract A potentiometric-titration procedure, in which samples are always exposed to an excess of I2-KI has been developed for measuring iodine-binding capacity of starches. Binding capacity of amylose under these conditions is ∼30% as opposed to 20% by conventional potentiometric titration. Spectrophotometric absorbance is essentially the same for either method, but is proportional to potentiometric values only in the excess-iodine titration procedure. Effects of variation of concentration of I2, KI, and phosphate buffer and of temperature on the reaction have been examined. Calculations based on concentration of reactants in solution indicate that the binding species varies from I3− at 10−1 m KI to I11− at 5 × 10−4 m KI.

Light-scattering and specific refractive increment behavior of amylose and dextran in methyl sulfoxide-water

Abstract Light-scattering measurements on polysaccharides in methyl sulfoxide or methyl sulfoxide-water are most reliable when made on a dialyzed solution-solvent system and when proper technique is used to remove the “micro gel” that seems unavoidably present when dried polysaccharide is dissolved in solvent. Discrepancies in published molecular weight-intrinsic viscosity relationships for amylose in methyl sulfoxide appear to be caused in part by differences the preparation and treatment of samples and possibly by differences in botanical source. The specific refractive increment of dextran is not a linear function of solvent composition in methyl sulfoxide-water. Measurements at osmotic equilibrium indicate that, over a moderate range of composition in methyl sulfoxide-water, dextran preferentially associates with about 2.5 molecules of water per glucopyranosyl residue of the polymer. Effects of long-term storage, sample treatment, and botanical source upon the specific rotation of amylose are examined.

Energy-Dispersive X-ray analysis of the mineral content of corn bran treated in vitro and by passage through the pig Gastrointestinal tract

Energy-dispersive X-ray (EDX) analysis was tested as a method for examining the mineral contents of corn bran loaded in vitro or passed through the GI tract of pigs. Particles of dry-milled corn pericarp treated in vitro or retrieved from the stomach, ileum, and colon of killed pigs were prepared as microtomed bulk specimens directly embedded in resin. Because of heterogeneity caused by differences in substrate cell density and mineral content, X-ray count averages for a number of different specimens had a coefficient of variation ⩾0.24.Detectable amounts of K, Ca, S, and P, but not Na, Cu, Fe, or Zn were found in specimens of initial bran. Although detectable concentrations of Cu, Fe and Zn could be loaded in vitro, these elements generally were not detected in bran retrieved from the pig GI tract. During GI tract passage, sodium was loaded onto bran mainly in the small intestine and unloaded in the large intestine. Calcium was loaded in the stomach and unloaded mainly in the small intestine. At each GI tract location, content of Na, Ca, K, and P in retrieved bran was greater than in the initial bran. EDX microprobe methods can be applied successfully to plant tissues treated in vitro and in vivo to investigate interactions with minerals in a diet.

In Vivo Mineral Contents of Dietary Fiber Determined by EDX Analysis

EDX measurements of the mineral content of oat hulls in the pig GI tract revealed that the hulls from the rectum contained more Na, P and S than prior to ingestion; while contents of K and Ca were not significantly different than in initial hulls. X-ray measurements indicated that potassium was the only element of the five examined which was unloaded from the initial oat hulls during passage through the GI tract. During this passage, the flows of Na and K into and out of oat hulls were proportional to concentrations of these elements in digesta. Although Ca was loaded onto oat hulls in the stomach, it was unloaded during subsequent passage, even though the concentration of Ca in digesta increased significantly in the large intestine. The behavior of corn pericarp generally was similar to that of oat hulls. We consider it unwise to attempt quantitative comparisons of corn pericarp behavior in our previous work (Dintzis et al., in press) with results in this study. The data bases are very small and feeding situations and diets were not equivalent. However, results from both studies show similar behavior in loading and unloading of Na, Ca, and S from the plant tissues, and possible differences with K and P. The finding that X-ray count values were different for oat hulls and corn pericarp when the tissues were loaded with equal amounts of calcium or potassium serves as a stark warning that additional work is required before measurements of this sort can provide quantitative results and a basis for comparisons between different plant tissues. Nevertheless, EDX analysis has provided information about the loading of Na, K, Ca, S, and P onto plant tissues during passage in the GI tract of growing pigs. The techniques used in this study appear worthy of further effort, for we believe they have the potential to provide significant information about in vivo interactions between plant tissues and minerals in the diet.

Total carbohydrate determination in dimethyl sulfoxide and guanidine hydrochloride as solvents

Abstract An automated total carbohydrate determination method based on phenol-sulfuric acid is presented for use with dimethyl sulfoxide or 4 M guanidine hydrochloride as solvents. The analysis system may be adjusted to yield linear optical density versus concentration plots up to concentrations of 100 μg carbohydrate/ml at concentration gradients of 10 μg/ml between samples. Sampling rates of 20 samples/hr and 30 samples/hr are used for 4 M guanidine hydrochloride and dimethyl sulfoxide, respectively.