Biodegradation of PVA-based formulations

Investigation of the biodegradability of water soluble poly(vinyl alcohol) (PVA) based blown films was carried out under different lab-scale environme ntal conditions. In particular respirometric tests were utilized in order t o evaluate the biodegradability of PVA films in composting, in modified Stu rm test and in soil burial simulation tests. Several microbial inocula pres ent in river water, mature compost, forest and farm soils as well as sewage sludge from municipal and paper mill wastewater treatments plants were uti lized for the relevant tests. A mixed PVA-degrading microbial culture was o btained by a common enrichment procedure by using sewage sludge from paper mill as inoculum; this culture was tentatively utilized for the isolation o f single PVA-degrading microorganisms. As a first result we can stress that significant biodegradation extent in fairly low incubation time can be obt ained only in the presence of acclimated microbial populations such as thos e deriving from paper mill sewage sludge, in liquid cultures. Nevertheless separation of single degrading microbial species was impossible most likely due to the establishment of symbiotic or commensal interactions between th e single components of the PVA-degrading mixed cultures. On the other hand, limited mineralization rates were recorded in solid cultures in the presen ce of soil or compost. Finally, a mechanism of degradation of polymer chain s unlike random or unzipping was suggested in the presence of either PVA-de grading mixed culture and its filtrate by means of viscometric determinatio ns of molecular weight within the time.