Chemistry: molecular biology and microbiology – Measuring or testing process involving enzymes or... – Involving hydrolase
Patent
1998-11-05
2000-06-06
Nutter, Nathan M.
Chemistry: molecular biology and microbiology
Measuring or testing process involving enzymes or...
Involving hydrolase
435 19, 435 23, 435262, 435832, 435836, 521 52, 521 77, C12Q 134, C12Q 144, C12Q 137
Patent
active
060717114
DESCRIPTION:
BRIEF SUMMARY
The invention relates to the complete degradation of moulded bodies, flat-shaped formations or foams consisting of polyester amides by means of enzymes.
Completely biologically degradable and compostable materials are gaining in importance. A great many polymers of this kind have been developed in recent years with the aim of providing a plastics material which can be recycled through composting. Various orders and standards which regulate the admissibility of such materials for composting or can prove that they can be safely composted (e.g. DIN standard 54 900) have at the same time been published. In this connection the term biological degradation always implies that in the presence of microorganisms the materials which are thus described are completely metabolised by the latter to form carbon dioxide and biomass.
It is known that polyester amides can undergo biological degradation (J. Appl. Polym. Sci., 1979, 1701-1711, U.S. Pat. Nos. 4,343,931, 4,529,792, JP 79 119 593, JP 79 119 594). Polyester amides which can be easily produced and are also completely biologically degradable are known from EP-A 641 817.
In the case of some plastics it is known that it is not just the growth of microorganisms on the polymer which proves that they are degradable, but that this can also be detected by means of enzymes. In this connection the test material is incubated with suitable enzymes and the degradation products are analysed (JP 56 022 324, DE-OS 2 632 007, Polymer Degradation and Stability, 1992, 241-248).
It has been found that polyester amides can be degraded by means of enzymes. However the discovered effect goes far beyond an enzymatic degradation to prove a basic biological degradability. It has surprisingly been found that selected enzymes are able to completely hydrolyse polyester amides. In this case the molecular weight of the polymer is reduced to such an extent that products made from it are completely decomposed. The enzymatic degradation takes place without any expensive buffering of the enzyme-containing solution. If, however, pure polyester is incubated with the enzymes which degrade it, the liberation of acid groups causes significant acidification. If the pH value is not maintained constant by buffering or adding lye, degradation soon stops, as most esterases and lipases cease to be active at low pH values.
The present invention provides a method for the enzymatic degradation of polyester amides, wherein the polyester amides are mixed with enzymes selected from the esterase, lipase and protease group in an aqueous solution, which may be buffered.
All enzymes which can break the ester and amide bonds in the polymer may basically be used to degrade the polyester amides.
The degradation takes place in an aqueous solution, which may be buffered. The pH value may lie between 3 and 11, preferably between 5 and 9, with a value between 7 and 8 being particularly preferred.
The following buffers, for example, may be used according to the invention: citrate, acetate, phosphate, formate, carbonate, trishydroxymethylamino methane, triethanolamine, imidazole, oxalate, tartrate, fumarate, maleinate, phthalate, succinate, ethylenediamine and mixtures of a plurality of these. Acetate, phosphate and citrate are preferably used as buffers.
The temperature at which the enzymatic degradation takes place may lie between 10 and 90.degree. C., preferably between 20 and 70.degree. C., with a temperature between 30 and 50.degree. C. being particularly preferred.
The method may be carried out in different ways:
The polymer is added to the aqueous enzyme-containing solution. The biologically degradable polymer may be added as a film, a sheet or in granular form. Moulded bodies may be added as a whole or comminuted. Coated or glued materials or materials in the case of which coatings have been applied or adhesive joints produced with polymers, such as, e.g. paper or board and coated paper or board, may be added to the enzyme-containing solution as a whole or in comminuted form.
The aqueous enzyme-containing solution may al
Bayer AG
Nutter Nathan M.
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