Biodegradation of poly(vinyl alcohol) based blown films under different environmental conditions

The biodegradability of water soluble poly(vinyl alcohol)(PVA) blown films was investigated under different environmental and test conditions. In particular respirometric determinations were utilized in order to evaluate the biodegradability of polymer films in composting, soil burial and aquatic degradation tests. Several microbial inocula derived from mature compost, forest and loamy soils as well as sewage sludges from municipal and paper mill waste-water treatments plants were matched with the PVA-based blown films. A fairly active PVA-degrading bacterial mixed culture was obtained by starting from sewage sludge of a paper mill as inoculum. Limited rates and extents of mineralization were recorded in solid cultures in the presence of either soil or compost samples, whereas significant biodegradation level within fairly short incubation time were obtained in liquid cultures in the presence of acclimated microbial populations. Experimental difficulties encountered in trials aimed at isolating single degrading microbial species definitely indicated the existence of strong symbiotic or commensal interactions between the single components of the PVA-degrading mixed culture. A PVA degradation mechanism different from random scission or unzipping of carbon backbone has been suggested on the basis of viscometric behavior of PVA solution in the presence of mixed culture and its filtrate. (C) 1999 Elsevier Science Ltd. All rights reserved.