Experimental and Computational Insights into Polyurethane Plastic Waste Conversion to Microbial Bioplastic

In this study, a seven-factor Hoke experimental design and the response surface methodology were used to optimize the fermentation conditions for the maximum polyhydroxyalkanoates (PHA) yield using polyurethane plastic waste (PUPW) as a source of carbon and energy for the microbial growth and biobased polyester production. The highest PHA yield (0.80 g/L ± 0.01) was obtained under a pH of 8; a temperature of 35 °C; a NaCl concentration of 5%; a PUPW concentration of 1%; an inoculum size of 15%, a monoculture of Pseudomonas rhizophila S211; and an incubation time of 6 days. The response values predicted by the Hoke design model at each combination of factor levels aligned with the experimental results, and the analysis of variance demonstrated the predictability and accuracy of the postulated model. In addition to the experimental evidences, P. rhizophila genome was explored to predict the PUPW-degrading enzymes and the associated protein secretion systems. Moreover, physicochemical properties, phylogenetic analysis, and 3D structure of S211 LipA2 polyurethanase were elucidated through an in-silico approach. Taken all together, integrated experimental tests and computational modeling suggest that P. rhizophila S211 has the necessary enzymatic machinery to effectively convert the non-biodegradable PUPW into PHA bioplastics.