Microplastics are fragments of plastic with a diameter of 5 millimeters or less. Coming from a variety of sources, these plastics adversely affect the aquatic environment by being digested by organisms and by releasing pollutants that attach during the plastic's journey into the ocean. Wastewater Treatment Plants (WWTPs) serve as a pathway for the microplastics to the aquatic environments, accumulating both cosmetic microbead plastics as well as particles from larger plastics, polyethylene being one of the most abundant plastic pollutants.

White rot fungus is a type of wood decay fungus that specifically targets lignin in wood, which is an organic polymer used for structure in plants. The enzymes, mainly Lignin Peroxidase (LiP) and Manganese Peroxidase (MnP), that are able to break down the lignin are also able to be applied to other polymers, such as plastic. In addition, white rot fungus uses these enzymes to produce reactive oxygen species, which are able to oxidatively degrade lignin and other organic polymers.

Fungal bioreactors have been used to treat mainly dye pollutants in WWTPs, but are thought to have greater potential for other pollutants. I am designing a fungal bioreactor using the submerged bed design, which includes a carbon source of cedar wood shavings, an air bubbling system to agitate the contents, a nutrient solution circulating through the reactor, all inoculated with Phanerochaete chrysosporium suspended in liquid medium. To test the polyethylene degrading ability, I will be using fluorescent green 106-125um polyethylene microbeads. Using imageJ software, I will be determining the average of all of the diameters of the microbeads before they are placed in the reactor, and after a week of placement in the reactor, and calculating a percent change.

After one week in the fungal bioreactor, the average diameter of the microplastics decreased by 27%, while the average diameter of the microplastics in the control bioreactor without fungus increased by 3%. Using an unpaired t-test, the change in the average diameter after treatment in the fungal bioreactor was extremely statistically significant, indicating that the fungal bioreactor was successfully able to degrade the microplastics. The results of the unpaired t-test for the control bioreactor was statistically significant, suggesting that the microplastics absorb liquid during their time in the bioreactor.

The small-scale submerged bed fungal bioreactor using Phanerochaete chrysosporium was able to degrade polyethylene microplastics within a timely manner. This white rot fungal bioreactor concept can be scaled up and used in water treatment in order to address the current microplastic problem that our planet faces.