There are several aspects that bring wonder when looking into the microscopic world. It has been long known that several different microorganisms can survive and thrive in the most extreme and hostile environments, from high heat to extreme cold and salty environments. Fungi are no exception to that, as numerous species have been identified that are either living or surviving in extreme conditions. Microorganisms that live in extreme environments are called extremophiles within the scientific community.
What is essential to the life of fungi?
Independent of growing in extreme or regular conditions, all fungi have some common requirements they need to fulfill. But even though we try to find these essential aspects, we often find species that worked out a clever way around those needs. However, some things can still be said with certain confidence here. First, like all living organisms on earth, fungi need water for the basic functions of the cell, and no fungi can live in a completely dry environment. Yes, some species have been found to be able to live in hot desert sands where water activity is extremely low, but it’s all due to mechanisms to retain the little existent water inside the living cells.
Another key essential component that all fungi need to grow is nutrients. For cells to duplicate and create more cells, they need access to all elements that will be used to create their building blocks: carbon, nitrogen, sulfur, potassium, and many other minerals in small amounts. Often, fungi obtain these from nature itself: minerals from soils, carbon, and nitrogen from decomposing other organisms. Sadly, fungi are not photosynthetic organisms, so they cannot capture carbon from the atmosphere, and unlike certain rare bacteria, they also cannot do it from electricity and air. But even though this is not true for carbon, some fungal species are known to get their nitrogen from the air we breathe. There is however, always something that the fungi needs to “eat” in order to grow, whether that is sugar, proteins, oils, or any other plant materials. And thinking about something that is crucial for us to live: oxygen, even though most fungi need it to thrive, many species have been found that do not require it: so-called “anaerobes”.
Other than these factors, there are species able to defy the rules of where organisms should be able to live.
In what kind of extreme conditions have fungi been found to live in?
Extremophile fungi have been known for decades, but subsequent discoveries never cease to surprise the scientific community. However, such organisms are highly difficult to isolate and grow in lab environments, and as such most species were only found in the past 15 years or so with the rise of next-generation sequencing projects that managed to capture the genetic information of virtually every organism present in a certain environment, independently if we are capable to grow them in a lab or not. To get an overview, we can look into scientific sources that cite numerous of these species under extreme environments:
- Cold environments such as environments at 0°C, arctic regions, and samples from dark ice listing almost 20 different species just from one source alone.
- Hot environments such as fungi live between 50°C and 80°C, as well as from hydrothermal vents and hot springs. These environments can easily have water above 100°C due to high pressures from large water volumes. To compare this, boiling water (at 100°C) is often used to sterilize different materials in the industry and daily life.
- Desert sands where there is almost no water, and temperatures vary between negative degrees to high heat. A study shows at least 600 species detected from samples of 3 different deserts, a few of them able to be grown in a lab environment.
- Highly acidic or basic pH. A wide variety of fungi was found in pH levels below 4 or up to pH 11. A high pH such as 11 is also often a sterilization mechanism in cleaning products such as soap or bleach, and the number of organisms growing in these conditions is quite rare.
- Deep-sea environments of over 3000 m depth, where high pressures and hostile conditions make it difficult for any organism to live.
How can this be useful for us?
The most common industrial application of extremophiles is to industrially obtain particular compounds they might produce, such as enzymes. The large advantage of using extremophiles is that these are able to grow in conditions that most other organisms cannot and, therefore, it’s easy to create fermentation conditions with a very small risk of contamination by environmental bacteria or yeasts. As an example for this, if for the purpose of a process you need to grow an organism that is able to grow at 70°C, you can use that temperature as a fermentation condition without much concerns for a sterile environment, since most environmental bacteria and yeasts will have optimal growth temperatures around 30-40°C, and very often die above 60°C.
Can fungi be a way to create food in the most inhospitable places?
If we merge the two realities of fungi growing in extreme conditions and fungi being used as a resource-efficient and healthy food source, it’s easy to come to the question: can we use fungi to create food in places where we cannot do agriculture?
The short answer is yes, but not directly for the reason one might be led to believe given the text above. Different fungal species have been discovered to be good targets for food production as mycoprotein, and most grow in mild fermentation conditions. Therefore, fungal growth for food production requires a production facility with a controlled environment, whether this is liquid fermentation bioreactors or solid-state fermentation in trays. This, however, is exactly what makes it possible to grow mycoprotein anywhere in the world. By relying on a production facility with controlled environments, it is possible to set up said facilities independent of climate or geographical features such as the presence of arable land. Remembering, of course, the hard requirement for the process to work is the availability of carbon and nutrient sources for the fungi to grow.
Luckily, certain species of fungi such as the one used by Mycorena, are highly robust to the type of substrates it can use as feedstock. Therefore, finding locally available carbon and nutrient sources is almost always possible, allowing the creation of decentralized systems of production.
Does this mean we could create nutritious food in the desert? In the artic? In space? In theory: definitely! But the real question is: what is the cost? In the calculations, we would need to consider how to bring water into the system, how to heat up or cool down the fermentation vessel to a favorable temperature, and how to acquire the substrate needed for the fungi to grow. Acquiring substrate will require transport of other resources if none are available nearby, and that might or might not be a problem depending on the region. As an example, it might be difficult to grow protein-rich crops in cold climates. However, sugar beets can grow in low temperatures and resist freezing weather. The high sugar content of sugar beets makes them a promising substrate for fungal growth, enabling the production of a protein-rich food produced from start to end in a cold-climate region. Furthermore, arable land in cold climates is often scarce, which only presents further opportunities for establishing a fermentation facility in non-arable lands, leaving the important soil for growing the needed crops.
What about the creation of food in space? First, there is the same problem as mentioned above, but at a much more massive scale: obtaining a carbon source. Would we transport sugar into space to use it as fungal feedstock? There is really no answer for this, but NASA is currently exploring options of how to transform Martian CO2 into sugar, so this can be used as a basis for fermentation processes. Then, we are often faced with another major problem: lack of oxygen. All fungi species identified today for mycoprotein production are aerobes, meaning they require oxygen for growth. For this, in a space environment oxygen needs to be produced, for which technologies exist nowadays such as the electrolysis of water and MOXIE. Overall, it’s not a simple challenge to solve, but at least it’s theoretically possible.
Back on earth, we see fungi as a unique solution to deliver decentralized food solutions around the world and decrease our vulnerability to increasing problems such as changing climates, broken supply chains, and increasing extreme conditions. All this by its robustness in using different feedstock sources, and the ability to grow almost anywhere in the world. Fungi are the food revolution!