Hunting down plastic-degrading microorganisms

Bacteria that can degrade the common plastic polyethylene terephthalate (PET) have been discovered in industrial waste water¹. The research, published in the journal Microbiology, offers insight into the conditions that lead to biological degradation of industrial equipment, and hope for a potential means of breaking down plastic waste.

PET is a widely used plastic that is clear, strong and lightweight, making it ideal for packaging foods and beverages, construction materials and vehicle parts. Despite being recyclable, however, PET is a significant component of the enormous amounts of plastic pollution found in marine and freshwater ecosystems.

Tamara Nazina and her microbiologist colleagues from the Research Center of Biotechnology of the Russian Academy of Sciences, in collaboration with materials scientists from the All-Russian Scientific Research Institute of Aviation Materials, went in search of water-borne microorganisms that can efficiently degrade PET.

"We used high-throughput gene sequencing and bioinformatics analysis to evaluate the diversity of bacteria on the surface of PET samples exposed to fresh recycled cooling water from a petrochemical plant, and compared it with samples exposed to seawater from the Black Sea and natural fresh water," says Nazina.

Their results showed that bacteria capable of degrading PET samples can be found in industrial waste water. Bioinformatics analysis showed that members of the genera Pseudomonas and Acidovorax growing in industrial waste water have the enzymes required to break down terephthalic acid, an intermediate metabolite of PET degradation. No PET-degrading bacteria were observed in seawater or fresh water.

In agreement with these results, when they examined the PET samples under a scanning electron microscope, they found noticeable degradation on the surface of PET samples incubated in waste water, but not in seawater. The results have important implications for the prevention of biofouling.

“Our findings suggest that waste water from petrochemical plants is a source of potential PET-degrading bacteria,” Nazina explains. “Industrial enterprises should therefore take into account the possibility of damage to plastic parts of equipment and carry out regular antimicrobial treatment.”

Isolating these specialized microbial communities could aid efforts to biologically break down PET. However, as the potential impact of plastic-biodegrading microorganisms on natural waters and surface reservoirs is unknown, the researchers suggest that discharge of recycled water from petrochemical plants should be monitored for such organisms.

“Our research will help not only in the isolation of promising biodegrading microorganisms, but also in the development of new standards for discharge of waste water containing such bacteria to ensure environmental safety,” Nazina concludes.