Carbon-chain polymers microbial degradation

In contrast to many other polymers classified as biodegradable, PVA exhibits a backbone solely made up of carbon. The presence of a heteroatom like O or N in the main chain is definitely not a prerequisite for Nature to handle a polymeric structure that does not exist in nature. PVA degradation starts with random oxidations of the polymer backbone in the extracellular or periplasmic space of some microbes. Specific enzymes able to detect such sites of first attack continue in a hydrolytic way, yielding ever smaller polymer fragments that finally can be metabolised by the microbe or the microbial community. 

For that reason microorganisms excrete enzymes into the environment, which can attach to the polymer surface and cleave the polymer chains, as long as the degradation products become short enough to be water soluble (this biological system has been developed by the evolution to use natural polymers or other poorly bio-available substrates for microbes). Then these intermediates can diffuse into the surrounding environment of the plastics, be incorporated into the microbial cells and metabolised there to form biochemical end products such as water and carbon dioxide (and many others). 

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