Degradation of polyester polyurethane by an indigenously developed consortium of Pseudomonas and Bacillus species isolated from soil

This work investigated the degradation efficiency of bacterial co-culture against polyester polyurethane in comparison to the individual strains. For this purpose, a consortium of two already reported polyester polyurethane (PU) degrading bacterial strains Bacillus subtilis MZA-75 and Pseudomonas aeruginosa MZA-85 was developed. The degradation was analyzed through measurement of weight loss, scanning electron microscopy (SEM), fourier transformed infra-red (FT-IR) spectroscopy and Sturm test (CO2 evolution test). Polyester PU degradation was augmented in the presence of co-culture, as indicated by maximum weight reduction in Polyester PU film pieces within 20 days. SEM micrographs showed surface changes in the polyester PU films in the form of pits or holes that resides bacterial cells. Besides degradation of soft segment, a new peak at 2250 cm−1 appeared in FTIR spectrum, which corresponds to free isocyanates due to breakdown of urethane linkages. The quantity of carbon dioxide evolved in Sturm test was much higher due to high degradation rate in co-culture vessel as compared to control as well as the separate cultures. A sharp increase in extracellular esterase activity of co-culture against polyester PU was observed. Butanediol (BD) and Adipic Acid (AA) were detected as degradation products in relatively higher intensity than those observed in pure culture, through gas chromatography-mass spectrometry (GC-MS). Hence, it is concluded that consortium might be better than pure cultures in polyester PU waste management and used as a tool for recycling purified monomers (biochemical depolymerisation/monomerization).