Biodegradation of aromatic-aliphatic copolyesters and polyesteramides by esterase activity-producing microorganisms

• Polyesteramide- and aromatic-aliphatic copolyester polymers were synthesized.
• Their biodegradability by esterase/lipase- producing microorganisms was investigated.
• Weak polymer mass reductions were detected, paralleled by an increase of toxicity.
• Electron microscopy showed breaks in aromatic-aliphatic copolyester caused by fungi.
• No breaks resulting from biodegradation were observed in polyesteramide polymers.

Biodegradability of polyesteramides prepared by anionic ring-opening copolymerization of ε-caprolactone and ε-caprolactam and of aromatic-aliphatic co-polyesters (PETP/LA) synthesized by solvolysis of poly(ethyleneterephthalate) with water solutions of lactic acid by microorganisms producing extracellular esterase and lipase was investigated. The bacterium Pseudomonas aeruginosa, yeast Candida guilliermondii and micromycete Aspergillus fumigatus exhibiting strong esterase and lipase activities on agar plates with artificial nitrophenyl substrates were selected to be used in six-week degradation experiments at 28°C. PETP/LA samples exhibited mass reductions of up to 5-10% in both the presence of the three microorganisms and in abiotic controls where the polymers were exposed only to Nutrient Broth or malt extract-glucose medium. Scanning electron microscopy revealed breaks in PETP/LA fibres when polymers were exposed to A. fumigatus and C. guilliermondii, attributable to microbial action. Polyesteramides were resistant to biodegradation. Degradation of both polymer types resulted in a 5-10-fold increase of toxicity of culture supernatans measured with Vibrio fischeri bioluminescence test and Sinapis alba germination plant test, as compared to the biotic and abiotic controls. No genetic toxicity was detected with Salmonella typhimurium His- test. The study suggests that ecotoxicity of compounds produced by biodegradation of polymers should be monitored.

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