Aerobic Biodegradation of Aromatic Aliphatic Copolyester Induced by Bacteria Obtained from Different Environments

In this study the biodegradation characteristics of aromatic aliphatic copolyester Ecoflex was assayed with five different bacterial strains isolated from different kinds of environments and living at diverse optimum of temperature. The biodegradation properties of selected strains (Brevibacterium luteolum, Bacillus thuringiensis, Aeromonas media, Geobacillus kaustophilus and Serratia sp.) were assessed through several plate assays oriented to their proteolytic, lipolytic, esterolytic and cellulolytic abilities; catalase activities were measured too. In addition the bacterial hydrolytic abilities for polyhydroxybutyrate, polylactic acid and polybutyrate adipate terephthalate were obtained using specific culture media including also a specific Ecoflex agar. The biodegradation dynamics of selected strains were evaluated mainly by the incubation of Ecoflex foils with a specific bacterium during a period from 3 days until 16 weeks and the change of the degradability of the Ecoflex surface in nitrogen has been assessed by nonisothermal chemiluminescence measurements from 40 to 250 A degrees C. Scanning electron microscope observation of inoculated foils was applied too. The comparison of the results showed the complexity of biodegradation phenomena. The concentration of oxygenated products measured by reached the maximum after 2 weeks of cultivation for strains G. kaustophilus and B. thurigiensis, after 4 weeks of cultivation for strain B. luteolum, and 8 weeks of cultivation for strains Serratia sp. and A. media. Each strain evidenced its own hydrolytic optimum at different periods, but almost all tested strains demonstrated a decline of hydrolysis up to 16 weeks of incubation. This study demonstrated that nonisothermal chemiluminescence examining momentaneous oxidation state of the polymer surface is a valuable technique to follow the biodegradation dynamics on polymeric film, while the Ecoflex agar is able to select useful polymer-degrading bacteria.