Molecular design of biodegradable functional polymers, 5: Enzymatic degradation of polycarboxylates containing vinyl alcohol blocks as biodegradable segment

Poly(sodium carboxylate)s containing vinyl alcohol blocks were prepared, and their microbial degradability and the poly(vinyl alcohol) (PVA) dehydrogenase activity as a function of vinyl alcohol block length in the polymer chain were analyzed. A clear relationship between the biochemical oxygen demand (BOD) biodegradability using the activated sludge and the relative activity of PVA dehydrogenase of a PVA-assimilating strain, Alcaligenes faecalis KK314, was observed. A vinyl alcohol block length of about 7 monomer units corresponds to the minimum chain length of the vinyl alcohol block length which acts as a biodegradable segment in the poly[(disodium fumarate)-co-(vinyl alcohol)]. The enzymatic cleavability of polycarboxylates containing vinyl alcohol blocks was estimated using the cell-free extracts of a PVA-assimilating microbial strain, A. faecalis KK314, as the PVA-cleaving enzyme source for both PVA dehydrogenase and hydrolase. The molecular weight of the polycarboxylates was reduced depending on the vinyl alcohol block length, and a similar molecular weight reduction tendency was observed with respect to the BOD values and PVA dehydrogenase activities.