Degradation mechanisms microbial

Sutherland JB, E Rafii, AA Kahn, CE Cerniglia (1995) Mechanisms of polycyclic aromatic hydrocarbon degradation. In Microbial transformation and degradation of toxic organic chemicals (Eds LY Young and CE Cerniglia), pp. 269-306. Wiley-Liss, New York. 

As in aquatic applications, weathering and hydrolysis are the dominant degradation mechanisms for terrestrial applications. Polymer articles covered with dirt can be problematic since photodegradation is not available however, the higher humidity levels and microbial activity in the soil when compared to the atmosphere are advantageous for degradation. 

Biological. A proposed microbial degradation mechanism is as follows 4-hydroxy-3-methylbenzyl alcohol to 4-hydroxy-3-methylbenzaldehyde to 3-methyl-4-hydroxybenzoic acid to 4-hydroxyisophthalic acid to protocatechuic acid to p ketoadipic acid (Chapman, 1972). In anaerobic sludge, diethyl phthalate degraded as follows monoethyl phthalate to phthalic acid to protocatechuic acid followed by ring cleavage and mineralization (Shelton et al, 1984). 

Chapman, P. J. (1979). Degradation mechanisms. In Proceedings of the Workshop Microbial Degradation of Pollutants in Marine Environments, ed. A. W. Bourquin P. H. Pritchard, pp. 28-66. Gulf Breeze, FL U.S. Environmental Protection Agency. 

Sutherland, J. B., Rafii, F., Khan, A. A. Cerniglia, C. E. (1995). Mechanisms of polycyclic aromatic hydrocarbon degradation. In Microbial Transformation and Degradation of Toxic Organic Chemicals, ed. L. Y. Young C. E. Cerniglia. New York ... 

Table 10.1 gives an overview of different aliphatic-aromatic copolyesters synthesised as degradable materials during the last few years. Part of the work reported in the literature dealt with hydrolytic degradation mechanisms which do not involve enzymic catalysis (chemical hydrolysis). This kind of degradation is often present in medical applications of polyesters, e.g., as implants in living tissues. Enzymic catalysed hydrolysis, in contrast, is usually connected to microbial degradation in the environment. 

Biomax is, according to the producer, a standard PET with addition of special monomers to allow degradation to take place. Comparable to PLA, the degradation mechanism is described as an initial attack of water to the special monomers which are sensitive to hydrolysis. Oligomers formed by this first abiotic degradation step can be transported into microbial cells and there be metabolised (Biomax is claimed to be (hydro/ biodegradable). 

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