Determination of the DS distribution of non-degraded sodium carboxymethyl cellulose by gradient chromatography

Sodium carboxymethyl celluloses as a cryoprotectant for survival improvement of lactic acid bacterial strains subjected to freeze-drying

This study investigated the possibility of sodium carboxymethyl celluloses (Na-CMC) in protecting the viability of lactic acid bacteria (LAB) against freeze-drying stress. 1 % concentration of Na-CMC with a 0.7 substitution degree and viscosity of 1500 to 3100 (MPa.s) was found to protect Lactobacillus delbrueckii subsp. bulgaricus CICC 6098 best, giving a high survival rate of 23.19 ± 0.88 %, high key enzymatic activities, and 28-day storage stability. Additionally, Na-CMC as cryoprotectant provided good protection for other 7 lactic acid bacterial strains subjected to freeze-drying. The highest survival rate was 48.79 ± 0.20 U/mg for β-GAL, 2.75 ± 0.15 U/mg for Na+-K+-ATPase, and 2.73 ± 0.41 U/mg for Ca2+-Mg2+-ATPase as 48.48 ± 0.46 % for freeze-dried Pediococcus pentosaceus CICC 22228. It was Interesting to note that the presence of Na-CMC reduced the freezable water content of the lyophilized powders containing the tested strains through its hydroxyl group, and supplied micro-holes and fibers for protecting the integrated structure of LAB cell membrane and wall against the freezing damage. It is clear that addition of Na-CMC should be promising as a new cryoprotective agent available for processing the lyophilized stater cultures of LAB strains.

Analysis of the Heterogeneities of First and Second Order of Cellulose Derivatives: A Complex Challenge

The complexity of the substituent distribution in polysaccharide derivatives is discussed and defined. The challenges regarding analytical characterization that results from various interrelated categories of distributions, including molecular weight, chemical composition, and microstructure, are outlined. Due to these convoluted levels of complexity, results should always be interpreted with carefulness. Various analytical approaches which have been applied to starch and cellulose derivatives are recapped, including enzymatic, mass spectrometric, and chromatographic methods. The relation of heterogeneities of first and second order among and along the polysaccharide chains is addressed. Finally, examples of own analytical work on cellulose ethers are presented, including the MS analysis of methyl cellulose (MC) blends and fractionation studies of fully esterified MC, especially its 4-methoxybenzoates by gradient HPLC on normal phase. Preparative fractionation according to the degree of substitution (DS) allows follow-up analysis in order to get more detailed information on the substituent distribution in such sub-fractions.

Effect of Synergistic Aging on Bauxite Residue Dust Reduction Performance via the Application of Colloids, an Orthogonal Design-Based Study

The application of polymer colloids is a promising approach for bauxite residue dust pollution control. However, due to the existence of synergistic aging, the efficiency of colloid dynamic viscosity to predict the dust control performance of bauxite residue is unclear. Previous studies were also rarely performed under synergistic aging conditions. Thus, this paper investigates the relationship between colloids’ viscosity and dust control performance under synergistic aging modes. Results illustrated that the binary colloid achieved better dust control performance than unitary colloid for their higher viscosity and penetration resistance. For both unitary and binary colloid, higher viscosity results in better crust strength. A logarithmic relationship was found for viscosity and dust erosion resistance under unitary aging. However, Only the dynamic viscosity of colloids in solid-liquid two-phase conditions, rather than dissolved in deionized water, can effectively predict the dust control performance under synergistic aging conditions.

Which average of copolymer composition does NMR provide?

While in molar mass determinations different averages are clearly distinguished, such differentiation is usually not performed when dealing with the composition of copolymers or polymer blends. The present article shows that the mol ratio calculated by nuclear magnetic resonance (NMR) usually provides neither a weight nor a number average. Only if the composition does not vary with molar mass, or if both copolymer units are of equal molar mass, a weight average mol ratio is obtained from NMR measurements. The frequent assumption that NMR yields a number average composition is incorrect, therefore. However, the mass fraction calculated from NMR corresponds to the weight average mass fraction.

Determination of the distributions of degrees of acetylation of chitosan

Chitosan is often characterized by its average degree of acetylation. To increase chitosan's use in various industries, a more thorough characterization is necessary as the acetylation of chitosan affects properties such as dissolution and mechanical properties of chitosan films. Despite the poor solubility of chitosan, free solution capillary electrophoresis (CE) allows a robust separation of chitosan by the degree of acetylation. The distribution of degrees of acetylation of various chitosan samples was characterized through their distributions of electrophoretic mobilities. These distributions can be obtained easily and with high precision. The heterogeneity of the chitosan chains in terms of acetylation was characterized through the dispersity of the electrophoretic mobility distributions obtained. The relationship between the number-average degree of acetylation obtained by solid-state NMR spectroscopy and the weight-average electrophoretic mobilities was established. The distribution of degrees of acetylation was determined using capillary electrophoresis in the critical conditions (CE-CC).

Application of two-dimensional chromatography to the characterization of macromolecules and biomacromolecules

Modern polymeric materials are heterogeneous with respect to different structural features, for instance molar mass, composition, and architecture. One-dimensional separation methods such as size-exclusion chromatography (SEC) are insufficient to fully resolve the multidimensional distributions of such complex materials. Therefore, two-dimensional separation methods are increasingly employed to characterize macromolecules. The present article describes in detail the advantages and experimental aspects of two-dimensional macromolecular separations. Selected examples will be discussed to explain the strategies used to separate macromolecules with respect to specific structural features.