Degradation, enzymatic

Biodegradable Plastics A degradable plastic in which the degradation results from the action of naturally occurring microorganisms such as bacteria, fungi, and algae. 

Degradable A material is called degradable with respect to specific environmental conditions if it undergoes the degradation to a specific extent within a given time measured by specific standard test methods. 

On the other hand, in ASTM D6400-04, compostabe plastic is defined as follow  

Compostable Plastic A plastic that undergoes degradation by biological processes during composting to yield carbon dioxide, water, inorganic compounds, and biomass at a rate consistent with other known compostable materials and leaves no visually distinguishable or toxic residues. 

Biodegradable plastics are expected to be used in the following areas (1) where plastics can be used in the natural 

STAGE I Water and lysozyme permeate into the chitosan structme followed by induction of swelling. Ihe degradation starts when the lysozyme cleaves -(1 4) glycosidic bonds to produce low-MW chitosan, chito-oligomers, and N-acetyl-D-glucosamine residues. Ihe low-MW fragments remain in the bulk till they reach a smaller size to get dissolved in the medium. 

STAGE II Ihe swelling reaches to its maximum and the degradation proceeds as the chitosan structure continues to decrease in MW. At this point, minute fragments are released into the surrounding medium resulting in a weight loss. 

The transient nature of the pharmacological actions of the enkephalins was noted early in opioid peptide studies, a fact that was soon correlated with 

The resistance of enkephalins to enzyme attack may be increased by substituting D-amino acids for glycine at the 2-position, by converting terminal C02H to an amide function, and by other modifications (see later). 

Recent work on enzymes of this kind is included in reports of the 1982 and 1983 International Narcotics Research Conference. 189  

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Solutions of methylceUuloses are pseudoplastic below the gel point and approach Newtonian flow behavior at low shear rates. Above the gel point, solutions are very thixotropic because of the formation of three-dimensional gel stmcture. Solutions are stable between pH 3 and 11 pH extremes wiU cause irreversible degradation. The high substitution levels of most methylceUuloses result in relatively good resistance to enzymatic degradation (16). 

At temperatures above Tm, chemical and enzymatic degradation of microbial exopolysaccharides is enhanced. The apparent enhanced stability of microbial exopolysaccharides in their ordered confirmation is thought to be due to the glycosidic bonds in the backbone of the polymer which raises the activation energy. This restricted movement would also restrict access of enzymes and chemicals to the backbone. 

Nonvolatile Inhibitors. Glycosides A number of toxic constituents are known to be released by the enzymatic degradation of various glycosides. Some of the volatile components have been mentioned previously—i.e., isothiocyanates from mustard oil glycosides and hydrogen cyanide from cyanogenic glycosides. 

Nagata M, Kiyotsukuri T, Ibuki H, Tsutsumi N, and Sakai W. Synthesis and enzymatic degradation of regular network aliphatic polyesters. React Fund Polym, 1996, 30, 165-171. 

Nagata M, Machida T, Sakai W, and Tsutsumi N. Synthesis characterization and enzymatic degradation of network aliphatic copolyesters. J Polym Sci A Polym Chem, 1999, 37, 2005-2011. 

Brooks, G.T. (1972). Pathways of enzymatic degradation of pesticides. Environmental Quality and Safety 1, 106-163. 

Borgatti M., Romanelli A., Saviano M., Pedone C., Lampronti 1., Breda L., Nastruzzi C., Bianchi N., Mischiati C., Gambari R. Resistance of decoy PNA-DNA chimeras to enzymatic degradation in cellular extracts and serum. Oncol. Res. 2003 13 279-287. 

Evidence of enzymatic degradation in vivo was first observed with a random copolymer of e-caprolactone and e-decalactone (93). 

This finding makes a significant contribution of enzymatic degradation to the overall degradation process highly unlikely. 

Enzymatic Degradation and Detoxification of Diethyl Phthalate by Fusarium oxysporum f. sp.pisi Cutinase... 

The purified fungal cutinase fiom F. oxysporum f. sp. pisi was kindly provided by Prof. C.M.J. Sagt in Utrecht University. The commercial product of esterase firom Candida cylindracea was purchased fi om Boehringer Mannheim (Germany). The enzymatic degradation of DEP... 

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