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 part icular respirometric determinations were utilized in order to evaluate the biodegradability of polymer films in composting, soil burial and aquatic de gradation tests. Several microbial inocula derived from mature compost, for est 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 star ting from sewage sludge of a paper mill as inoculum. Limited rates and exte nts of mineralization were recorded in solid cultures in the presence of ei ther soil or compost samples, whereas significant biodegradation level with in fairly short incubation time were obtained in liquid cultures in the pre sence of acclimated microbial populations. Experimental difficulties encoun tered in trials aimed at isolating single degrading microbial species defin itely indicated the existence of strong symbiotic or commensal interactions between the single components of the PVA-degrading mixed culture. A PVA de gradation mechanism different from random scission or unzipping of carbon b ackbone has been suggested on the basis of viscometric behavior of PVA solu tion in the presence of mixed culture and its filtrate. (C) 1999 Elsevier S cience Ltd. All rights reserved.