Assessing biodegradability of plastics based on poly(vinyl alcohol) and protein wastes

Research was conducted into biodegradability of mixed polymer films based on poly(vinyl alcohol), protein hydrolyzate (collagen hydrolyzate from wastes after chrome tanning) and glycerol in an aqueous aerobic environment. Evaluation. of biodegradation was based on carbon dioxide produced in the gas phase. Pure PVAL was degraded by a current mixed culture for water-treatment (unadapted) only after an approx. 10-day lag phase; during breakdown of mixed film the protein component and glycerol were broken down first and PVAL degradation occurred in the second stage. Biodegradation could be well described by 1st-order formal chemical kinetics. Repeated degradation by an adapted culture proceeded in a single stage with considerably shorter lag phase (< 30 h) at a simultaneously approx. 1.5-fold greater breakdown rate (rate constants). During degradation of substrates containing PVAL, microbiological tests proved an approx. 100-fold increase in numbers of PVAL-degrading bacteria. Added protein hydrolyzate + glycerol in PVAL contributed to increasing biodegradability more than followed from proportional representation of individual components. (C) 2002 Elsevier Science Ltd. All rights reserved.