7. Microbial biodegradation of polyurethane

Polyurethane (PU) is a general term used for a class of polymers derived from the condensation of polyisocyanate and polyol. Polyurethanes are an important and versatile class of manmade polymers used in a wide variety of products in the medical, automotive and industrial fields. Depending on the chemical structures of the polyisocyanates and polyols, PU can adopt various forms ranging from flexible to rigid and from low density to solid elastomer. Over three-fourths of the global consumption of PU is in the form of foams amounting to approximately 5 % of the total amount of plastic produced. Despite its xenobiotic origin, PU has been found susceptible to biodegradation by naturally occurring microorganisms. Microbial degradation of PU is dependent on the many properties of the polymer such as molecular orientation, crystallinity, cross-linking and chemical groups present in the molecular chains which determine the accessibility to degrading-enzyme systems. Several reports have appeared in the literature on the susceptibility of PU by fungal attack. Results varied from fungal isolates utilizing colloidal polyester PU as the sole carbon and energy source and displacing esterase activity to their inability to grow solely on PU and the enzymes having to be induced. The majority Correspondence/Reprint request: Dr. Gary T. Howard, Department of Biological Sciences Southeastern Louisiana University Hammond, Louisiana 70402, USA. E-mail: [email protected]