When cleaning up an ocean oil spill, it's best to use a material that separates the oil from the seawater. Scientists have created a new type of organic membrane extracted from the oyster mushroom. First, there are now "Janus membranes", which are hydrophilic on one side (absorbing water) and hydrophobic on the other (repelling water but absorbing oil). When used in a filtration system, these membranes draw in contaminated water from one side and expel it from the other side, while retaining the drawn-in oil.
However, such membranes are often made from petroleum-based materials that are not very environmentally friendly and do not biodegrade once discarded. With this shortcoming in mind, scientists at Saudi Arabia's King Abdullah University of Science and Technology (KAUST) turned to mushrooms.
More specifically, they studied mycelium, the fungus' web of hyphae (also known as hyphae) from which true mushrooms (also known as fruiting bodies) sprout when conditions are right. Importantly, mycelium contains proteins called hydrophobins, which are hydrophilic on one side and hydrophobic on the other.
Doctoral student Joyce Cavalcante and her supervisor Professor Gyorgy Szekely first cultured the mother mycelium from fresh king oyster mushrooms. They then placed mycelial colonies from the mother species on a film made of a hydrophilic polymer filled with nanoscale pores.
These pores allow the hyphae to draw nutrients from the gel-like growth medium on the other side of the film, but the pores are so small that the hyphae cannot grow directly through the film.
As the hyphae grow on one side of the film, their hydrophilic side is adsorbed by the hydrophilic polymer, causing their hydrophobic side to move upward away from the hydrophilic polymer. Therefore, when the mycelium finally peels away from the polymer film, they form a biodegradable organic film with one hydrophilic side and one hydrophobic side.
When tested on water contaminated with crude oil, the membranes were found to absorb 445% more oil than traditional polypropylene Janus membranes, while also absorbing 99.6% less water.
"These findings raise hope for next-generation membranes with greater selectivity and adsorption capabilities," Cavalcante said.
The research was described in a paper recently published in the Journal of Materials Chemistry.