Acid Hydrolysis, enzymatic

Figure 10. Data on the heterogeneous acid hydrolysis, enzymatic hydrolysis, and photochemical decomposition of regenerated cellulose. (Reproduced with permission from Ref. 16. Copyright 1966 TAPPI.)...

Technically, acid hydrolysis is often preferred (except for acid-labile hormones), because the process offers simplicity and speed and usually results in complete hydrolysis regardless of the nature of conjugates. Enzymatic hydrolysis requires special attention to factors such as optimal concentration and type of enzyme, pH, temperature, and duration of incubation. In addition, the possible presence of enzyme inhibitors, which vary in amount and nature with different specimens, may affect the completeness of hydrolysis. In spite of potential problems, enzymatic hydrolysis is used for plasma analysis of steroids that are labile in strong acid solution (e.g., pregnanetriol and corticosteroids), and because it prevents interference from substances that are produced by acid hydrolysis. Enzymatic hydrolysis, for example, has been used successfully to determme the urine concentration of estrone and the plasma concentration of estrone sulfate in postmenopausal women. 

Comparing variable Dilute-acid hydrolysis Enzymatic hydrolysis... 

In comparison with acid hydrolysis, enzymatic hydrolysis is a preferable approach to convert biomass substrate into fermentable sugars. Cellulose and hemicellulose can be hydrolyzed by an enzyme complex generated from fungi or other microorganisms. Fig. 9.2 shows the changes in appearance of (a) the cellulosic fiber before pretreatment (b) an easily hydrolyzable parenchyma cell attached with the fiber (c) the broken stmcture of the biomass after pretreatment and (d) the remaining solids of the substrate after hydrolysis. 

There are mainly three methods used for isolating CNWs from raw cellulosic materials, including acid hydrolysis, enzymatic hydrolysis and 2,2,6,6-tetramethylpiperidine-l-oxyl radical (TEMPO) mediated oxidation. In cellulosic materials, it is only pure in cotton fibers, whereas cellulose in wood and other plants always exists in combination with other materials such as lignin and hemicelluloses. 

Technology Description Hydrolysis is the process of breaking a bond in a molecule (which is ordinarily not water-soluble) so that it will go into ionic solution with water. Hydrolysis can be achieved by the addition of chemicals (e.g., acid hydrolysis), by irradiation (e.g., photolysis) or by biological action (e.g., enzymatic bond cleavage). The cloven molecule can then be further treated by other means to reduce toxicity. 

It is well known that the 1-phosphates of the ketoses, L-fuculose (51) and L-rhamnulose (52) have considerable biochemical interest. Their chemical synthesis has not been described as far as is known to the writer, but the rate of acid hydrolysis of L-fuculose 1-phosphate, obtained by enzymatic synthesis, has been determined by Heath and Ghalambor (20) and that of L-rhamnulose 1-phosphate by H. Sawada (48) and by Chiu and Feingold (II). They found that the rate of... 

Partial hydrolysis of a peptide can be carried out either chemically with aqueous acid or enzymatically. Acidic hydrolysis is unselective and leads to a more or less random mixture of small fragments, but enzymatic hydrolysis is quite specific. The enzyme trypsin, for instance, catalyzes hydrolysis of peptides only at the carboxyl side of the basic amino acids arginine and lysine chymotrypsin cleaves only at the carboxyl side of the aryl-substituted amino acids phenylalanine, tyrosine, and tryptophan. 

Hie ester linkage of aliphatic and aliphatic-aromatic copolyesters can easily be cleaved by hydrolysis under alkaline, acid, or enzymatic catalysis. This feature makes polyesters very attractive for two related, but quite different, applications (i) bioresorbable, bioabsorbable, or bioerodible polymers and (ii) environmentally degradable and recyclable polymers. 

The degradation of agrochemicals during storage may result from a variety of factors such as acidic and alkaline hydrolysis, enzymatic action, etc. It is recommended that a preliminary stability study be performed for the chemical in the environmental sample. If the chemical is stable under acidic conditions, for example, samples can be stored after acidification with hydrochloric or phosphoric acid. 

A specific approach for the measurement of base damage to DNA involves the hydrolysis of DNA into monomeric units. Acidic hydrolysis leads to the release of bases while enzymatic treatment yields nucleosides. The resulting mixture of lesions together with the overwhelming presence of normal bases or nucleosides is resolved by chromatography. The targeted damage is then quantified by use of specific detection systems. 

Identification of flavonoids Quantification of individual flavonoids depends heavily on the availability of standard references. Only a limited number of common flavonoids are commercially available as standards. Standard references for flavonoid glycosides are particularly difficult to find thus direct quantification of the native glycosides is nearly impossible. Analysis of the aglycones after acid or enzymatic hydrolysis is therefore common practice. When standard flavonoids are not available, or when unknown compounds are encountered in a particular fruit or vegetable, use of a DAD... 

In a note on the decomposition of cellulose by a mixed culture of Vibrio perimastrix, Perlin and Michaelis84 reported about 5.6% of filter paper was fermented in 8 days. The agreement between this percentage and the percentages of accessible cellulose in native cellulose as found by hydrolysis may be fortuitous. However, there is enough similarity in acid and enzymatic hydrolysis to warrant further work along this line. 

Smirnova et al. [5] have described a simple non-enzymatic method of quantitative determination of adenosine triphosphate in activated sludge from aeration tanks. Extraction of the nucleotides in boiling distilled water was followed by removal of the protein impurities by acidification. Barium salts of di- and triphosphates of the nucleotides were precipitated and the precipitate was washed and dissolved in acid to convert the barium salts to sodium salts. The quantity of adenosine triphosphate was determined quantitatively by inorganic phosphorus in the liquid over the precipitate before and after acid hydrolysis, and by ultraviolet absorption spectra. The method was tested in activated sludge from operational sewage works. There was good agreement between the adenosine triphosphate content determined spectrophotometrically and by phosphorus, despite the presence of small quantities of secondary impurities. 

The amidocarbonylation of aldehydes provides highly efficient access to N-acyl a-amino acid derivatives by the reaction of the ubiquitous and cheap starting materials aldehyde, amide, and carbon monoxide under transition metal-catalysis [1,2]. Wakamatsu serendipitously discovered this reaction when observing the formation of amino acid derivatives as by-products in the cobalt-catalyzed oxo reaction of acrylonitrile [3-5]. The reaction was further elaborated to an efficient cobalt- or palladium-catalyzed one-step synthesis of racemic N-acyl a-amino acids [6-8] (Scheme 1). Besides the range of direct applications, such as pharmaceuticals and detergents, racemic N-acetyl a-amino acids are important intermediates in the synthesis of enantiomeri-cally pure a-amino acids via enzymatic hydrolysis [9]. 

By forming intramolecular and intermolecular hydrogen bonds between OH groups within the same cellulose chain and the surrounding cellulose chains, the chains tend to be arranged in parallel and form a crystalline supermolecular stracture. Then, bundles of linear cellulose chains (in the longitudinal direction) form a microfibril which is oriented in the cell wall structure. Cellulose is insoluble in most solvents and has a low accessibility to acid and enzymatic hydrolysis (Demirbas, 2008b). 

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