Biodegradation of polyvinyl alcohol by thai indigenous mixed microbial culture

Abstract

PVA is biodegradable plastic and a water-soluble synthetic polymer that plays a significant role in industry. A large amount of PVA in wastewater causes heavy environmental pollution in terms of accumulation, disposal, and long-term degradation; therefore it must be removed from wastewater before the water is discharged. In this study, NS3 mixed microbial culture, capable of completely degrading 5 g.L-1 polyvinyl alcohol (PVA), was isolated from landfill soil using the enrichment culture method. It completely degraded PVA at an initial concentration in the range 1-5 g.L-1 over 5-20 days of incubation with continuous shaking at 30 °C. Moreover, mixed microbial cultures were found to remove PVA at a high range concentration of 10-25 g.L-1. Urea and glucose added to the medium inhibited PVA degradation by increasing the pH to a strongly alkaline level, which would cause cell viability and enzyme stability. The FT-IR spectra and SEM imaging revealed the mechanisms and the physical degradation of PVA films, respectively. PVA uptake in bacterial cells produced a dent in the cell surface, which represented the consumption of PVA by bacterial cell. The PVA-degrading mixed microbial culture is the first reported in Thailand and can be beneficial in PVA wastewater treatment.