Hydrolysis surface

Another likely commercial starch is that from amaranth seed, an expanding crop for food use, particularly its flour. Amaranth starch granules (1—3 micrometers dia) have potential for numerous food appHcations, one of which is as a fat replacer because of their small size and especially after minor surface hydrolysis with a-amylase or glucoamylase to produce a fluffy surface (see Fat replacers). 

Fischer-Colbrie, G., Matama, T., Heumann, S. et al. (2007) Surface hydrolysis of polyacrylonitrile with nitrile hydrolysing enzymes from Micrococcus luteus BST20. Journal of Biotechnology, 129, 62-68. 

Surface hydrolysis Surface complexation Surface ligand exchange Hydrogen bond formation... 

Surface complexation models for the oxide-electrolyte interface are reviewed two models for surface hydrolysis reactions are considered (diprotic surface groups and monoprotic surface groups) and four models for the electric double layer (Helmholtz,... 

Gouy-Chapman, Stern, and triple layer). Methods which have been used for determining thermodynamic constants from experimental data for surface hydrolysis reactions are examined critically. One method of linear extrapolation of the logarithm of the activity quotient to zero surface charge is shown to bias the values which are obtained for the intrinsic acidity constants of the diprotic surface groups. The advantages of a simple model based on monoprotic surface groups and a Stern model of the electric double layer are discussed. The model is physically plausible, and mathematically consistent with adsorption and surface potential data. 

Although adsorption of many types of species could be considered, this discussion will focus on surface hydrolysis reactions, that is, adsorption of H+ and OH . Virtually all surface hydrolysis experiments are carried out in the presence of a "background electrolyte," many of which appear to exhibit weak specific chemical interactions (e.g., ion-pair formation) with the surface (10-12). While consideration of these interactions is essential to a complete understanding of the interfacial chemistry, the topic is a subject in itself, and will not be considered in detail here. Treatment of these interactions is readily incorporated within the framework that is presented here. 

Figure 3. Surface hydrolysis and formation of surface hydroxyl groups.

Equations 9-14 provide the framework for combining either of the two surface hydrolysis models that were presented with any of the four electric double layer models to define the interface model completely and to solve for all unknown potentials, charges, and surface concentrations. In the following section some specific limiting cases are considered. 

Two models of surface hydrolysis reactions and four models of the electrical double layer have been discussed. In this section two examples will be discussed the diprotic surface group model with constant capacitance electric double layer model and the monoprotic surface group model with a Stern double layer model. More details on the derivation of equations used in this section are found elsewhere (3JL). ... 

Diprotic Surface Groups. Most of the recent research on surface hydrolysis reactions has been interpreted in terms of the diprotic surface hydrolysis model with either the triple layer model or the constant capacitance model of the electric double layer. The example presented here is cast in terms of the constant capacitance model, but the conclusions which are drawn apply for the triple layer model as well. 

Three methods have been used for interpretation of surface hydrolysis data, the first two of which involve approximations and reduction to linear form Method I assumption that on the acidic... 

Figure 7. Covariability between values of C and Kd yielding best fit of diprotic surface hydrolysis model with constant capacitance model to titration data for TiC>2 in 0.1 M KNOj (Figure 5). The line is consistent with Equation 29. The crosses represent values of C and log found from a nonlinear least squares (NLLS) fit of the model to the data, with the value of capacitance imposed in all cases the fit was quite acceptable. The values of and C found by Method I (Figure 6) also fall near the line consistent with Equation 29. The agreement between these results supports the use of the linearized model (Equation 29) for developing an intuitive feel for surface reactions.

Hydrolases in Polymer Chemistry Part III Synthesis and Limited Surface Hydrolysis of Polyesters and Other Polymers... 

Keywords Cutinase Polyacrylonitrile Polyamide Polyethyleneterphthalate Surface hydrolysis... 

Table 1 Monitoring enzymatic surface hydrolysis of polymers...

Recently, improved hydrophilicity and dyeability with acid and disperse dyes of nylon 6 fibres after treatment with protease (subtilisin) was reported [31]. Similarly, various proteases were used for surface hydrolysis of nylon 6,6 fibres, leading to... 

Generally, enzymatic hydrolysis of nitriles to the corresponding acids can either proceed stepwise, which is the case for catalysis by the nitrile hydratase/amidase enzyme system, or in one step in the case of nitrilases. Both systems have been investigated for surface hydrolysis of PAN [10], Complete hydrolysis with either system was monitored by quantification of ammonia and/or polyacrylic acid formed as a consequence of hydrolysis of nitrile groups [70-72], As a result, considerable increases in colour levels (e.g. 156% for commercial nitrilase) were found upon dyeing [72],... 

Apart from nitrile-hydrolyzing enzymes, some esterases and cutinases have been used for surface hydrolysis of PAN [74], These enzyme were shown to specifically hydrolyse vinyl acetate moieties present as co-monomer in many commercial PAN materials, with no changes in crystallinity as determined by X-ray diffraction [74],... 

Eberl A, Heumann S, Brueckner T et al (2009) Enzymatic surface hydrolysis of poly (ethylene terephthalate) and bis(benzoyloxyethyl) terephthalate by lipase and cutinase in the presence of surface active molecules. J Biotechnol 143 207-212... 

Fischer-Colbrie G, Matama T, Heumann S et al (2007) Surface hydrolysis of polyacrylonitrile with a nitrilase of a new strain of Micrococcus luteus. J Biotechnol 128 849-857... 

Guebitz GM, Cavaco-Paulo A (2008) Enzymes go big surface hydrolysis and functionalisation of synthetic polymers. Trends Biotechnol 26 32-38... 

Almansa E, Heumann S, Eberl A et al (2008) Enzymatic surface hydrolysis of PET enhances bonding in PVC coating. Biocatal Biotrans 26 365-370... 

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