Isolation of mesophilic bacterium for biodegradation of polypropylene

• A mesophilic polypropylene degrading strain was isolated and identified as Stenotrophomonas panacihumi PA3-2.
• S. panacihumi PA3-2 biodegraded not only Low molecular polypropylene but also high molecular polypropylene.
• S. panacihumi PA 3-2 biodegraded polyethylene, even though it was isolated as polypropylene degrading strain.

A mesophilic bacterium capable of polypropylene (PP) biodegradation was isolated from soil using a culture medium containing low molecular weight polypropylene (LMWPP) as a carbon source. The biodegradation of LMWPP and high molecular weight polypropylene (HMWPP), by the isolated bacterium, was measured under compost conditions. As produced PP has a broad molecular weight distribution so that it contains molecules with a wide spectrum of chain length, ranging from extremely low molecular weight to very high molecular weight. As the extremely low molecular weight fraction of PP may produce misleading results on biodegradability of PP, Soxhlet extraction using toluene was performed to obtain HMWPP, by dissolving out the extremely low molecular weight fractions from PP as produced from a commercial scale polymerization reactor. Previous research on PP biodegradation used PP compounded with pro-oxidants or with natural polymers, such as starch, or pretreated commercial-grade PP containing various additives, such as heat and light stabilizers. In contrast, the present study employed PP without any additives, to examine the true biodegradability of neat PP, excluding any effects of the additives.