Enrichment and isolation of microbial strains degrading bioplastic polyvinyl alcohol and time course study of their degradation potential

Abstract

Polyvinyl alcohol (PVA) degrading bacterial strains were isolated from various environmental sites rich
in plastic wastes by using the enrichment culture technique. Among the various isolated strains, the
selected potent PVA degrading bacterial strains were tentatively characterized as Bacillus and Pseudomonas sp. The time course of the PVA degradation potential of the characterized strains in growth media containing PVA as a major carbon source was evaluated using the spectropho-tometric assay method. This was done by determining the residual PVA remaining in the culture media, increase in cell growth and change in pH of the media over a period of twenty days. The ultimate biodegradation (mineralization) of PVA to its mineral constituents CO₂ and H₂O was determined by the CO₂ evolution test. The strain characterized as Bacillus sp. showed 65% of PVA degradation as determined by spectrophotometric assay and 45.4% of mineralization of PVA over a period of 20 days. The strain characterized as Pseudomonas sp. showed 42% of PVA degradation as determined by spectrophotometric assay and 28.9% of mineralization of PVA over a period of 20 days.

Key words: Polyvinyl alcohol (PVA) degrading bacteria, isolation, ultimate biodegradation, mineralization.