How much is melanin  worth 

The New Black Gold

Empa researchers have succeeded in extracting large quantities of the pigment melanin from fungi. The gigantic honey fungus in the service of science is one of the largest living things in the world. The applications of the "black gold" range from wood preservatives to the construction of musical instruments and water filters.

Its properties are amazing and its applications correspondingly diverse: the pigment melanin, which, for example, protects human skin from damaging UV rays (and gives us a summery tan), is a veritable treasure trove of new materials and technologies. Although the miracle substance occurs in nature, the complex biopolymer could only be produced artificially on an industrial scale in expensive and complex processes in which not all properties are reproducible. Processes to obtain natural melanin from microorganisms have so far also shown a low yield. So it is not surprising that the substance is many times more expensive than gold. Empa research team have now got mushrooms to produce the "black gold" in a very simple and  highly scalable process.

An extraordinary mushroom produces 1000 times more melanin than previously known

In their search for simpler, cheaper processes for producing large quantities of natural melanin, Schwarze and his team came across a fungus that is actually found in the forest as a plant pest: Armillaria cepistipes, the bulbous honey fungus. Its amazing metabolism binds heavy metals, makes wood glow in the dark - and produces melanin. And en masse. "We have selected a promising line of honey fungus that, with our technology, now produces around 900- 1,000 times as much melanin as other microorganisms with which pigment production has already been attempted," says Schwarze. The trick: the selected fungus strain lives in a nutrient liquid and releases the melanin into the environment. “This system now enables sustainable production, which no longer requires complex extraction steps as in the case of previous microbiological procedures," explains Empa researcher Javier Ribera, who is significantly involved in the process. After three months, one liter of honey fungus culture has already produced around 20 grams of melanin.

The facilitated and sustainable production of melanin now enables Empa researchers to advance projects for the development of innovative materials. These include, for example, a water purification system: Since melanin is able to bind heavy metals, it can be used to develop new types of water filters. "We integrated the organic melanin into artificial polymers such as polyurethane," explains Empa researcher Anh Tran-Ly. Using electrospinning, the polymer mixture was spun into the finest fibers to form membranes. The Empa team discovered that up to 94% lead can be removed from polluted water using the melanin-based composite membranes.

In nature, fungi use melanin pigmentation, among other things, to protect themselves from competing organisms that invade from the environment. With a new technology, the coloring substance can now also be used to protect much larger communities from human influence: melanin can be used to protect tropical forests in which the valuable ebony grows. Tropical ebony is also considered to be particularly valuable because of its unique dark colour. A sustainable process that upgrades ordinary native spruce wood into a product that is just as visually attractive allows vulnerable tropical forests to breathe a sigh of relief. 

Serpentino - The little snake among the instruments

Since the honey fungus uses melanin as a weapon against conspecifics, it makes sense to use this move to protect wood from harmful fungi. In order to develop a melanin-based wood protection, the Empa researchers are involved in a recently started interdisciplinary research project that is supported by Innosuisse, the Swiss Agency for Innovation Promotion. They want to recreate a historical wind instrument, the serpentino (in English: small snake).

In addition to the Northwestern Switzerland University of Applied Sciences and the Basel Historical Museum, the project partner is the company SBerger Serpents in Le Bois (JU), which is responsible for the practical implementation of the research project. Company founder Stephan Berger is enthusiastic about the rebirth of the rare instrument: "The serpentino was used over 400 years ago and was the inspiration for modern instruments such as the saxophone and tuba," he explains. Although it is a playful challenge for the musicians to master the instrument, the sound is incomparable, enthuses Berger. "The serpentino produces sounds that are rich in overtones and very touching." Originally, the wind instrument was used in churches to support singing,

Although today a trend towards historically informed performance practice means that the Serpentino is in demand, Berger cannot supply its customers with instruments: the peculiarly curved original instruments have become rare. Because inside the walnut snake there is not only an incomparable sound - there is also a war raging: the condensation from the breath of the musicians creates a humid microclimate that provides excellent conditions for the growth of all kinds of pests. And so microbes and fungi decompose the centuries-old instruments and gradually destroy the last original specimens.

The original Serpentino replicas of the research project should be protected from this damage in the long term. This is where the Empa researchers' melanin comes into play: "If we can use a melanin-based wood preservative impregnation, it's not just the newly built Serpentinos that can be saved from decay," says Berger. Other woodwind instruments that are built today with local, less resistant woods could also benefit from such a protective layer. Therefore, the cooperation with the Empa team for instrument construction is exciting in two respects.

Background: melanin, honey fungus and serpentino

"Melanin" is a generic term for a large group of coloring substances. The pigment melanin gives our hair, eyes and skin their colour. It is found in bird feathers, sheep's wool and squid ink. In addition, plants, fungi and even bacteria have access to the miracle substance. Its task: to protect the organism from environmental and other stress. Darkening of the skin when exposed to the sun is an example of this. Mushrooms, on the other hand, are given an even more amazing ability by melanin: Thanks to melanin, they can even use radioactivity to generate energy in their own metabo 

Helping trick from the mushroom box

So that the black coloring can penetrate the wood better, the researchers resorted to another trick from their mushroom box: the watery polypore, Physisporinus vitreus, which causes white rot, is also a wood pest. It grows like a sponge on trees and decomposes the supporting lignin in the wood. Using a process specially developed at Empa, the wood is now treated with the white rot fungus for just long enough for the melanin suspension to penetrate deep into the wood structure, but the wood still remains stable.

Honey fungus - the largest living thing in the world

It is called the honey fungus or honey fungus and it is one of the most amazing creatures on earth. Inconspicuously, it may sprout in the classic mushroom shape on the forest floor, decorated only with a decorative bar around the handle, like a bracelet, which gives it the Latin name "Armillaria".

Much more impressive, however, is his net of black strands, which he pulls over the wood and the floor. Mushroom filaments join together to form meter-long, thick bundles, surrounded by a protective layer containing black melanin, and look for new habitats and sources of food. These so-called rhizomorphs can also invade tree roots as parasites, climb up the trunk and decompose their host from the inside. With a size of several square kilometers, the largest living creature in the world, a 2400-year-old honey fungus network, stretches out in the US state of Oregon. In Switzerland, on the other hand, Europe's largest mushroom can be found on the Ofen Pass. After all, this honey fungus covers an area the size of 50 football pitches. It also owes its age of around 1000 years to the pigment melanin, which protects the black fungus threads from environmental damage.