What is a mushroom substrate?

Le substrate for mushrooms is the material or mixture of materials that serves as a nutrient base and physical support for growing mushrooms. Unlike plants that grow in soil, mushrooms need an organic substrate rich in specific nutrients (in particular carbonaceous matter such as cellulose and lignin, and a sufficient proportion of nitrogen) to develop. In nature, this substrate for fungi can be decomposing wood, forest humus, manure, straw or various organic debris. In controlled cultivation, these conditions are reproduced by preparing optimised substrates for each species grown.

A good mushroom substrate must fulfil a number of functions: provide the nutrients required for mushroom growth, retain sufficient moisture while remaining aerated, and offer a physical structure that the mycelium can easily colonise. The substrate is generally packaged in the form of "bundles or blocks (compressed bags or solid blocks of substrate) ready to be inoculated with mycelium, or already incubated depending on the case. For professional growers, substrate management is a crucial stage that influences the entire growing cycle, from mycelium incubation to mushroom harvesting.

The different types of growing substrates

There is no single mushroom substrate suitable for all species of mushroom. Each type of fungus has evolved to decompose certain organic materials, so the choice of substrate depends on the species being cultivated. However, substrates can be categorised into broad families, based on their main component:

• Straw-based substrates Straw (especially wheat or rye straw) is a classic substrate for many wood-eating fungi such as oyster mushrooms. Chopped and then moistened, straw forms a fibrous base that the oyster mushroom mycelium quickly colonises. It is often pasteurised to eliminate most competing organisms before sowing. Straw can be used on its own or enriched with wheat bran to improve its nutritional value.
• Wood-based substrates (sawdust, shavings) Mushrooms such as shiitake, reishi and other exotic species prefer a substrate based on hardwood sawdust (oak, beech, etc.) or shavings, simulating the decomposition of dead wood. Supplements such as cereal bran are generally added to provide nitrogen. This type of mushroom substrate often requires a sterilisation or extensive pasteurisation, because pure sawdust has a high C/N ratio (high carbon, low nitrogen) which is corrected with nitrogenous additives, thereby increasing the risk of contamination.
• Composted substrate (manure + straw) Compost: This is the famous compost used for button mushrooms (Agaricus bisporus). It is made from horse or poultry manure mixed with straw, which undergoes a controlled fermentation process over several weeks. This mushroom compost provides a very nutrient-rich medium when ripe. After composting, we add a layer of potting compost of goblet (casing) on top to induce the fruiting of button mushrooms. This mushroom substrate is specific to so-called "bedding" mushrooms (Agarics), which have different needs to wood-eating mushrooms.
• Alternative and recycled substrates : Many initiatives use recycled materials as a substrate for mushrooms. For example coffee grounds can be used as a base for growing certain oyster mushrooms, as can crop residues (bagasse from sugar cane, cocoa shells, etc.). These substrates make the most of organic waste and are part of an ecological approach. However, they may be less consistent in composition and often require rigorous treatment (pasteurisation or sterilisation) to avoid contaminants.

The table below compares a number of commonly used substrates and their characteristics:

Type of substrate	Cultivated mushrooms	Benefits	Constraints
Pasteurised straw (bales)	Oyster mushrooms, pholiotes (e.g. Nameko), shiitake mushrooms	- Abundant, inexpensive - Rapid colonisation of the mycelium	- Must be pasteurised (60°C) to prevent mould formation - Can dry out without the right humidity - Large storage capacity
Enriched sawdust (oak, beech + wheat bran)	Shiitake, Reishi, Maitake, oyster mushrooms	- Reproduces the natural environment of wood-eating fungi - Gradually releases nutrients over time - Allows high yields over several harvests	- Requires extensive sterilisation or pasteurisation (high risk of contamination when bran is added) - Raw material sometimes more expensive (food-grade sawdust)
Fermented manure compost	Button mushrooms (Agaricus)	- Very rich in nutrients after fermentation - Proven traditional mushroom substrate for Agarics - Available in large industrial volumes	- Long, technical preparation (fermentation over ~2 weeks + pasteurisation) - Specific use for Agarics (ineffective for oyster mushrooms, etc.) - Requires casing (compost) to bear fruit
Recycled materials (coffee grounds, agricultural waste)	Oyster mushrooms, trials on other species	- Recovering organic waste (sustainable approach) - Low or negative cost if waste - Interesting as a complement to other substrates	- Variable composition depending on the source (less regular) - Limited supply volumes for industrial crops - Often very rich in nutrients, so contamination is possible without appropriate treatment

Note: Whatever the type of mushroom substrate, it is almost always necessary to treat the substrate before seeding to prevent undesirable moulds or bacteria competing with the cultivated mushroom. There are two methods pasteurisation (heating the mushroom substrate to 60°C for 12 to 48 hours), which eliminates the majority of germs while retaining a few bacteria that are "allies" of the fungus, or the sterilisation (heating above 100°C in an autoclave), which eliminates 100 % from the organisms, but then requires inoculation under strict sterile conditions. In the industrial production of substrates in large quantities, tunnel pasteurisation is often preferred for its efficiency and lower cost, while sterilisation is more often reserved for substrates packaged in small volumes (jars, filter bags) in the laboratory, at least in Europe.

The qualities of a good mushroom substrate

Not all substrates are created equal. For a mushroom substrate to perform well, it must combine several essential qualities:

• Balanced nutritional content : The mushroom substrate must provide sufficient carbon (in the form of cellulose, hemicellulose and lignin) and a little nitrogen to support fungal growth. A ratio of Carbon/Nitrogen (C/N) of around 30:1 is often cited as a minimum for wood-eating fungi such as oyster mushrooms. Below this ratio (too much nitrogen), the production of fungi is certainly encouraged, but there is a risk of bacterial proliferation. Above it (too much carbon), the mushroom substrate may limit fruiting due to a lack of rapidly assimilable nutrients. Enrichment with wheat bran or other supplements must therefore be measured precisely.
• Good water retention while remaining aerated: Mushrooms need moisture (around 60 to 70 % of water in mushroom substrate) to grow, but also oxygen. The ideal substrate acts like a sponge: it retains water without becoming soggy, and it remains porous enough for the mycelium to breathe. A texture that is too compact or too much stagnant water can lead to asphyxiation of the mycelium or the development of rot.
• pH adapted : Most edible mushrooms thrive in a slightly acidic to neutral mushroom substrate (pH around 6.0 to 7.0). An unsuitable pH can prevent the mycelium from colonising effectively. For example, some people grow oyster mushrooms on straw by adjusting the pH with lime (lime pasteurisation method) to discourage contaminants and favour the target fungus.
• Homogeneous physical structure favourable to colonisation : Well-mixed ingredients, the right particle size (finely shredded straw, sawdust that's neither too fine nor too coarse) and bagging that's well-packed but not excessively compact - all contribute to rapid, uniform colonisation of the substrate by the mycelium. A mushroom substrate of industrial quality is prepared according to precise recipes to guarantee this homogeneity.
• Low contamination pressure : A good substrate for mushrooms is one own. This means using healthy raw materials (non-mouldy straw, fresh sawdust free of mould), treating them correctly (sufficient pasteurisation) and inoculating them with a vigorous mycelium under controlled hygiene conditions. A quality mushroom substrate can also be recognised by its very low contamination rate during incubation (few or no bags that ferment or mould).

When you buy a ready-to-use mushroom substrate from a specialist supplierThese quality criteria are normally strictly adhered to. The substrate producer has implemented controls at every stage to provide mushroom growers with an optimal, pathogen-free substrate that is repeatable from one batch to the next.

The impact of mushroom substrate on yield

The choice of mushroom substrate and its quality have a major influence on the performance mushroom cultivation. The yield from a block of substrate can vary between 20 and 45% depending on the different types of substrate (on straw or on sawdust and wood shavings). This means that for a 12 kilo block of substrate, for example, the number of kilos harvested from a block can vary between 2.4 and 5.4 kilos of mushrooms harvested.

In practical terms, a high-quality mushroom substrate means :

• Faster incubation the mycelium quickly colonises a well-formulated substrate, reducing the time between sowing and fruiting. For example, oyster mushrooms can colonise a straw-based pasteurised substrate in around 2 weeks, ready to start fruiting, whereas on a substrate of lower quality or poorly prepared, the mycelium will take longer and run the risk of competing with other micro-organisms.
• Faster start to fruiting When the mushroom substrate is well colonised, the right climatic conditions (humidity, temperature, aeration) are all that's needed to induce the formation of primordias (young mushrooms). With a good quality, well-incubated substrate, the first flight (first harvest) comes early. For example, substrates incubated of oyster mushrooms or shiitake mushrooms supplied by Eurosubstrat can be harvested for the first time in 8 to 10 days only after they have been received in the mushroom house, thanks to the lead taken by incubation.
• More abundant harvests The optimum substrate provides the mushroom with all the energy it needs to produce a beautiful flush of mushrooms. On oyster mushrooms, a first flush can represent 30 to 50 % of substrate weight. In other words, a 15 kg bundle of substrate can yield 4.5 to 7.5 kg of oyster mushrooms from the first harvest. With shiitake, an initial flush of around 15 to 25 % is also common. A mediocre substrate, on the other hand, will give a leaner or irregular flush.
• More cycles A healthy, nutritious substrate can support several harvest cycles (flushes). Many commercial producers do not keep oyster mushroom substrates beyond 2 or 3 flushes because productivity decreases and the risk of infection increases with time. However, getting two good flushes on a substrate before replacing it is a good quality standard. A poor-quality mushroom substrate could run out or become contaminated after just one small flush, which increases costs (it has to be replaced more quickly to restart production).

In short, investing in a high-quality substrate means you can be sure of better, more regular yieldsThis means greater profitability for the mushroom farm. On a professional scale, a few percent more yield or a few days saved on the production cycle can make a big difference over the year.

Producing your own substrate vs. buying a ready-to-use substrate

Faced with the size of the substrate, a mushroom grower may hesitate between make your own substrate in-house or buy ready-to-use substrate from a supplier. Each option has its advantages and constraints, and the choice often depends on the size of the farm, the technical skills available and the production targets.

Produce your own substrate means mastering the whole chain: obtaining the raw materials (straw, sawdust, bran, etc.), having the facilities to process them (grinder, pasteuriser or autoclave), knowing how to prepare balanced mixtures, then inoculating and incubating everything in a clean environment. The advantage is total control over the mushroom substrate recipe and independence from suppliers. However, it does require heavy investment (equipment, energy, sterile preparation rooms), the working time and specialist expertise. The risk of failure (contamination, poorly balanced substrate giving low yields) is not negligible without solid experience in applied mycology.

Buying a ready-to-use substrate from a specialist supplier offers the advantage of greater simplicity and reliability. The substrate generally arrives either pre-incubated (already colonised by mycelium, ready to bear fruit) or sterilised/pasteurised and ready for sowing. For growers, this means they can concentrate on the climatic management of fruiting and harvesting, without having to manage the upstream substrate preparation phase. Mushroom substrate may cost money to buy, but it guarantees optimised performance and considerable time savings. What's more, a good supplier will often provide invaluable technical support.

From the point of view of profitability Unless they have a very large-scale operation that justifies in-house production, many B2B growers opt to buy turnkey mushroom substrate. This allows them to have a regular supply of high-quality substrates, to increase the number of growing cycles per year (since each substrate purchased is ready more quickly for harvesting) and to secure their production. The table below summarises the differences between these two approaches:

Production stages	With ready-to-use substrate (supplier)	With "home-made" substrate (manufactured in-house)
Preparing the mixture	Produced by the supplier using an optimised recipe. No initial handling for the grower.	At the producer's expense: purchase of ingredients, grinding, mixing according to a personal recipe.
Treatment (pasteurisation/sterilisation)	Professionally processed in the factory, guaranteeing a clean substrate (pasteurised in a tunnel or sterilised in an autoclave, as appropriate).	Requires specialised equipment (pasteurisation chamber, industrial autoclave) and trained staff. High energy and logistics costs for each batch prepared.
Seeding (inoculating with mycelium)	If incubated substrate: already made in the factory under controlled conditions, the block is received. seeded and incubated. If substrate not seeded: often supplied with mycelium for incorporation or ready for easy seeding.	Must be done manually or semi-auto in a very clean area (or in a sterile laboratory if the substrate is sterilised). Quality seed mycelium must also be obtained. High risk of contamination if done incorrectly.
Incubation of mycelium	If incubated substrate: partially or fully incubated during transport (under refrigeration) or at the customer's premises in a short time. Saves several weeks on the total cycle.	To be managed on site: requires air-conditioned incubation rooms at 20-28°C for 2 to 8 weeks, depending on the species. Space occupation and daily monitoring to control contamination.
Time to fruiting	Very short - a professionally incubated substrate can be put in the culture room and produce a flock in ~10 days.	Long - between substrate preparation, seeding and incubation, it can take 4 to 10 weeks to obtain a substrate ready to fruit.
Efficiency and reliability	Optimised: substrate formulated for high yields, vigorous mycelium, low failure rate. Technical support from the supplier in the event of problems.	Variables: depend on the expertise of the grower and the quality of the mycelium used. Risk of lower yields if the recipe is poorly balanced or if contamination occurs.

In short, the purchase of ready-to-use substrates is often the preferred solution for professional mushroom growers who want to secure and develop their production. The supplier takes care of the complex stages, and the grower can focus his efforts on the care of fruit-bearing (temperature control, hygrometry, CO2, lighting) and on the marketing mushrooms. This collaboration enables us to achieve a high level of quality and consistency in our harvests, which is essential if we are to meet the orders of our demanding customers.

EUROSUBSTRAT CALLAC: the guarantee of a high-performance mushroom substrate

As a supplier of mushroom substrates recognised in Europe, EUROSUBSTRAT CALLAC is the partner of choice for growers looking for a top-quality mushroom substrate. Our company, based in Brittany (France), has over 30 years' experience in the production of incubated mushroom substrates. These are our strengths and the added value of our mushroom substrates:

• Proven expertise and know-how EUROSUBSTRAT CALLAC is one of the European leaders in incubated substrates for exotic mushrooms. Since 1995, we have been perfecting our recipes and processes to provide producers with ever more effective substrates. This long experience enables us to provide our customers with the best possible advice and to constantly innovate.
• Substrates formulated for performance Our mission is to produce a substrate for mushrooms from high quality, as regular as possibleto guarantee our customers high yield and consistent. In practical terms, our pasteurised incubated substrates produce an average first harvest (flush) in just 8 to 10 days, with a yield of between 18 % and 30 % of substrate weight from this first flush (depending on the species grown). This level of performance is the result of optimised formulation and strict control of incubation.
• Consistent quality thanks to selected ingredients Quality control starts with a rigorous selection of raw materials. With 95 % of French origin, the straw, oak sawdust and wheat bran used in our substrates are chosen according to strict specifications. For example, our supplies of straw and other supplements come from trusted suppliers, ensuring optimum cleanliness and consistency. Each batch of mushroom substrate is therefore homogeneous and reliable.
• A controlled industrial process Our production process consists of 7 rigorous stages (grinding/mixing, fermentation, pasteurisation, inoculation in blocks, incubation in chambers, cold storage, preparation and dispatch). Throughout this process, quality controls are carried out: computerised monitoring of pasteurisation temperatures, colonisation tests, checking for contamination. This level of control guarantees that the substrates delivered to you are healthy, well colonised with the right mycelium and ready to produce.
• A range tailored to your needs : EUROSUBSTRAT CALLAC offers substrates for a variety of species of cultivated mushrooms. In particular, we have incubated substrates for several varieties of oyster mushroom (grey oyster mushroom, yellow oyster mushroom, pink oyster mushroom - organic or conventional), for the shiitake (different adapted strains, organic or conventional), as well as for more specific fungi such as the pholiote. In addition, thanks to our trusted partners, we also supply button mushroom compost (for brown Agaricus) as well as goblet soil, to serve mushroom growers who want to diversify their production. Whatever species you grow, we have a suitable mushroom substrate solution ready to use.
• Controlled, international delivery : We deliver our substrates in France and throughout Europe (more than half our production is exported). To ensure that the substrate blocks arrive in perfect condition, we work with partner transporters equipped with temperature-controlled lorries. Pallets of substrate travel between 2°C and 4°C, keeping the mycelium relatively dormant during transport. As a result, the substrate is not depleted en route and you receive fresh, fully-performing blocks. Our production capacity (more than 12,000 tonnes a year) and our logistical responsiveness mean we can meet high-volume requests, while guaranteeing delivery times.
• Service quality and technical support Choosing EUROSUBSTRAT CALLAC means not only getting an excellent product, but also support. Our team knows that each mushroom house has its own specific characteristics. That's why we offer a personalised technical supportWe offer a wide range of services, including cultivation advice, on-site visits and telephone discussion sessions. If you have any questions about growing substrates, optimising cultivation parameters or any unforeseen problems, our mycology experts are at your side. This support is an integral part of what we offer, because your success is our success.

In short, EUROSUBSTRAT CALLAC is a trusted ally for professional mushroom growers. By entrusting us with the supply of your substrates, you are choosing peace of mind and performance: you will receive top-of-the-range substrates that will enable you to maximise your harvests, while benefiting from the advice of a company that is an expert in the sector.

Technical support to optimise your cultivation

Growing mushrooms can involve a number of hazards (variations in temperature, humidity, unforeseen contamination, etc.), but you are not alone in facing these challenges. As a B2B partner, Eurosubstrat makes it a point of honour to supporting its grower customers throughout their productions. On request, we can programme training, technical site visits to assess your facilities and cultivation protocols, or simply to assist you by phone to solve a specific problem.

This tailor-made support aims to optimise your performance These include improving yields, solving fruiting problems and advising on the layout of new growing rooms. For a mushroom farm, being able to draw on the expertise of the mushroom substrate supplier is a valuable asset. It's like adding a bit more mycological expertise to your team, without having to hire someone directly.

Finally, we encourage you to make contact with our specialists to discuss your specific needs. Whether you're starting up a mushroom farm or are an established grower looking to expand capacity, we'll be happy to guide you to the most suitable mushroom substrate solutions and help you grow successfully.