Fungi show promise against microplastics in water

"Fungi have unique environmental applications due to their diversity and robustness," Susie Dai says. (Credit: Getty Images)

A new study identifies a potential way to remove microplastics from water with fungi.

“Although fungal pelletization has been studied for algae harvesting and wastewater treatment in the past decade, to the best of our knowledge, it has not yet been applied for the removal of microplastics from an aqueous environment,” says Susie Dai, an associate professor in the plant pathology and microbiology department at Texas A&M University. “This study examines their use for that purpose.”

Microplastics, tiny plastic particles resulting from commercial product development and the breakdown of larger plastics, have gained increasing attention in recent years due to their potential harm to the ecosystem. With the continual increase of global plastic production, pollution from this persistent waste contaminant group derived from synthetic polymers presents a significant environmental challenge.

While the health risks posed by submicrometer microplastics to humans are not yet fully understood, those studying them generally believe the overall risk associated with submicrometer microplastics—those less than a micron in a specified measurement—is higher than that of larger plastics. They hypothesize this is due in large measure to their greater potential for long-range transport and ability to more easily penetrate the cells of living organisms.

“Previous studies have indicated that submicrometer microplastics can easily travel considerable distances in the environment, infiltrating plant root cell walls,” says study leader and postdoctoral scientist Huaimin Wang. “They have even been shown to have been transported into plant fruiting bodies and human placenta.”

Besides microplastics generated from direct human activity such as cosmetic and industrial production, nanoplastics—synthetic polymer particulates ranging from 1 nanometer to 1 micrometer in diameter—can also be generated from the fragmentation or degradation of larger plastics.

A significant portion of microplastics generated from human activities end up in sewage and wastewater treatment plants. While these plants can remove the vast majority of them, many of the submicrometer particles are unfiltered.

“The microplastics and nanoplastics removed after activated sludge treatment can be further removed by additional conventional methods such as coagulation, disk filters, and membrane filtration,” Dai says. “But enriched microplastics still pose a waste-management challenge.”

Unfortunately, she says, some disposal methods like landfill interment or incineration are not environmentally favorable for reintroducing these back into the natural carbon cycle.

For the study, three fungal strain candidates were chosen based on their speed of growth, dye degradation, spore production, and pellet formation. Two were newly isolated white rot fungi strains.

The study yielded encouraging findings on removing polystyrene and polymethyl methacrylate microplastics and nanoplastics—ranging from 200 nanometers to 5 micrometers in the aquatic environment—using these isolated fungal strains.

“These types of microplastics and nanoplastics are among the most common,” Dai says.

The three strains showed a high rate of microplastic removal and exhibited potential microplastic assimilation. “The microplastics attach to the surface of the fungal biomass, which makes it easier to remove them from water as part of the pellet,” Dai explains.

Wang says that due to the unique capacity of the selected white rot fungal strains to form pellets, they should be suitable for remediating microplastics. “They may also have the potential for use in upgrading wastewater treatment plants and as a cost-effective means to further remove microplastics and minimize the pollution by plastics in natural water bodies,” he says.

The current study using fungus to remove microplastics is compatible with Dai’s previous research using fungus to remediate PFAS or “forever chemicals” in the environment.

“Fungi have unique environmental applications due to their diversity and robustness,” Dai says. “They have also been useful in our ability to develop a novel bioremediation technology for these chemicals, which can threaten human health and ecosystem sustainability.”

PFAS are used in many applications ranging from food wrappers and packaging, to dental floss, fire-fighting foam, nonstick cookware, textiles, and electronics.

Dai’s new technology uses a plant-derived material to absorb the PFAS and dispose of them by means of microbial fungi that literally eat them.

The United States Department of Agriculture Forest Service’s Northern Research Station also participated in the study, which appears in Bioresource Technology Reports.

Source: Texas A&M University