There is a growing importance in the need to find economically viable alternative energy sources to fossil fuels. Biofuel derived from biomass (which is any organic material coming from any form of life or its derived metabolic products) is one of the options. A major setback for these type of energy crops though is that they compete with our food sources for farmland and water. The significance of finding sustainable solutions is so great that researchers have become very creative in coming up with ways to bring us power through alternative methods… like bionic mushrooms capped with a network of cyanobacteria and graphene.
First off, what is cyanobacteria and what is graphene, and how are they connected to energy production?
Cyanobacteria are possibly the most successful group of microorganisms on the planet. They generate energy from sunlight through photosynthetic mechanisms. They can also generate energy in the dark relying on sugar degradation via respiratory mechanisms. Because of this, they can survive almost anywhere, and in any ecosystem, making them the most genetically diverse.
Recently, scientists have discovered that cyanobacteria have a tremendous potential to be the producer of the third generation of biofuels. What makes cyanobacteria better than other biomass energy sources is that microalgae cultures do not compete with agriculture. This means that they require neither bio-productive lands nor freshwater, and possess higher yield per hectare. It is a non-food biomass source for energy supply, thus making it one of the most promising feedstocks for bioenergy generation.
Graphene is a freshly discovered (2004) nanomaterial with a unique combination of exceptional properties. Not only is it one of the best electrical conductors on Earth, but it is also one of the thinnest and strongest materials there is. Furthermore, it is optically transparent, yet so dense that it is impermeable to gases – not even helium, the smallest gas atom, can pass through it.
The downfall to cyanobacteria becoming an energy producer is that the organisms can’t survive on artificial surfaces. Mechanical engineers Manu Mannoor and Sudeep Joshi of the Stevens Institute of Technology found a way around this, with mushrooms. Mushrooms already host several other forms of microbial life, and could, therefore, provide the right environment — nutrients, moisture, pH, and temperature — for cyanobacteria to thrive. Therefore, the cyanobacteria can survive longer while generating electricity.
A white button mushroom equipped with 3D- printed graphene nanoribbons (black), which collects electricity generated by densely packed 3D-printed cyanobacteria (green) Credit: Sudeep Joshi, Stevens Institute of Technology
Sudeep Joshi, a postdoctoral researcher and author of the study, tells the story of how the idea came to be: “One day my friends and I went to lunch together and we ordered some mushrooms. As we discussed them, we realised they have a rich microbiota of their own, so we thought why not use the mushrooms as a support for the cyanobacteria. We thought let’s merge them and see what happens.”
They went to the grocery store and bought a pack of white button mushrooms. Then the scientists went back to their lab and began construction. They started by 3-D printing an electronic ink containing graphene nanoribbons onto the cap of a living mushroom. Then, they printed a bio-ink containing cyanobacteria on top of that. With the two layers overlapping, the electronic ink and cyanobacteria ink intersected. Where they intersected energy-producing electrons could move through the outer membranes of the bacteria to the conductive network of graphene nanoribbons.
“In this case, our system — this bionic mushroom — produces electricity,” said Manu Mannoor, an assistant professor of mechanical engineering at Stevens. “By integrating cyanobacteria that can produce electricity, with nanoscale materials capable of collecting the current, we were able to better access the unique properties of both, augment them, and create an entirely new functional bionic system.”
The mushroom was able to create a current of about 65 nanoAmps which alone is not enough to power a device. But, When several cyanobacteria-covered mushrooms are wired together they generated enough electricity to light up a small LED.
In an email to USA TODAY, Mannoor said they integrated the microbes and mushroom in a way that “the cyanobacteria is able to make the energy by photosynthesis while the mushroom provide it with the suitable ‘shelter’ to do so. The features of this shelter include moisture, biophysiological conditions suitable for the bacteria to live longer, as well as the geometry of the mushroom’s head that give ample sunlight.”
Densely packed cyanobacteria (green) achieved via 3D printing increases electricity-generating behavior Credit: Sudeep Joshi, Stevens Institute of Technology.
Another interesting possibility Joshi told the BBC was, “Right now we are using cyanobacteria from the pond, but you can genetically engineer them… to produce higher photocurrents… It’s a new start; we call it engineered symbiosis. If we do more research in this we can really push this field forward to have some type of effective green technology.”
Bionic Mushrooms might just be the future of efficient and cost-effective fuel production from biomass. It could help decrease our current dependence on conventional energies, which are both scarce and polluting, as well as be an improvement to other things: “With this work, we can imagine enormous opportunities for next-generation bio-hybrid applications,” Mannoor says. “For example, some bacteria can glow, while others sense toxins or produce fuel. By seamlessly integrating these microbes with nanomaterials, we could potentially realize many other amazing designer bio-hybrids for the environment, defense, healthcare and many other fields.”
The work is reported in the Nov. 7 issue of Nano Letters, a peer-reviewed journal from the American Chemical Society. It is part of a broader effort to better improve our understanding of cells biological machinery. Then how to use those intricate molecular gears and levers to fabricate new technologies and useful systems for defense, healthcare and the environment.