A novel poly(vinyl alcohol) (PVA) degradation pathway was demonstrated such that the hydroxy group of PVA was first dehydrogenated into the corresponding carbonyl group to form the beta-hydroxy ketone moiety which was followed by the aldolase-type cleavage to produce the methyl ketone and the aldehyde terminals by the PVA-assimilating strain, Alcaligenes faecalis KK314. Both the biodegradation steps of dehydrogenation and subsequent aldolase-type cleavage were catalyzed by the same protein having 67 kDa as the holoenzyme and apoenzyme of PVA dehydrogenase, respectively.