BIULETYN PRODUCENTA PIECZAREK PIECZARKI 2/2015 s.14-21 Translation
In the next three issues of the Bulletin I would like to describe the problem of growing mushrooms based on controlled process of its nutrition in a series of three articles. This article describes the process of nutrition. In the next; the second of this series, the process of controlling the behavior of mushrooms will be described, and the third will be on raw materials, tillage and technologies used in mushrooms cultivation. Understanding the fundamental processes of life of mushrooms, especially its nutrition and ways of controlling it allows for efficient use and development of the proposed new technology.
Why current technology based on Dutch experience does not have development potential in Poland?
The classical approach states that the substrate is the basis for obtaining high yields of mushrooms. This means that it should be of a high abundance of nutrients necessary for its yield and stable quality. The requirement of stable quality is not being met in Poland in relation to the Phase III substrate. Let me remind you that the country produces a substrate based on straw and chicken manure under high diversity of quality of raw materials and in highly variable climatic conditions during the year. In this situation, an integral part of the production of Phase III compost is incorporating protein supplements. They provide the expected high abundance of nutrients and stable quality. What the concept of stabilization of the compost by the use of protein supplements is based on? Con Hermans explains it in the article Compost (2) „Good compost needs good nutrients” published in Mushroom Business number 23 (April 2015 p. 4 to 6). Rich compost can be considered as one which has a specific content of nitrogen. In case where it is too low, protein supplements are used to obtain a stability of its contents. They enrich it with nitrogen. As a consequence of using a protein supplement on the substrate with poor content of nitrogen the yield could be increased up to 8 kg\m2. With substrate with the average content of nitrogen the increase is up to 3 kg\m2. In case of nitrogen-rich substrate it is unprofitable. In the article there is no information, at which level the amount of supplement these effects can be achieved. There are no indications in Hermans’ article of ways to practically determine the dose of supplement to obtain desirable effects and not to suffer losses when it is introduced unnecessarily. What further complicates the use of protein supplements has to assess the quality of the substrate through the C\N ratio. While this ratio is important at the initiation of composting and during evaluation of Phase I and II substrate it is significant, the situation with Phase III substrate is quite different. The phase III substrate is a mixture of Mushroom spawn and undecomposed compost. It means that, by determining the level of nitrogen in the Phase III substrate one is specifying its contents in the spawn and substrate but there is no way of knowing how the nitrogen is distributed among them. This makes it quite difficult to ascertain doses of the supplement. It is worth noticing that using maximum dose of a protein supplement for compost rich in nitrogen can lead to a reduction in yield.
In practice, the maximum size of a protein supplement dose does not exceed 1.25% of weight of the substrate. The basic dose is 1.0%. The limitation of the dose is due to the inability to control the temperature of the substrate after application of the casing soil when the doses are higher and in particular, when the compost is not fully colonized by the mushrooms spawn. As a rule, one does not differentiate between doses of protein supplement because of the characteristics of compost, unless upon request of the recipient.
To summarize the use of protein supplements does not allow for the elimination of variable richness in nutrients and stable quality of compost. Fluctuations in the yield of the phase III substrate are still considerable and reach up to 10 kg\m2. Besides, average annual yield higher than 32 kg\m2 cannot yet be achieved.
As a starting point for creating new technologies of growing mushrooms assumption is made that its yield depends on the mass of the spawn in the first and second flush, and in the third and the rest flushes depends on the activity of thermophilic organisms in the compost; Scytalidium thermophilum coexisting with Mushroom after spawn’s growth (cold composting phase). During the period of mushroom’s yield the activity of enzymes is much less important.
To live, grow and reproduce mushrooms need:
- Water. It has several functions: it is a component of the cell sap, transports nutrients, and controls temperature. Active water is of particular importance, but its role in the diet has not been fully elucidated.
- Nutrients. They are collected in the form of aqueous solutions:
- energy substances – a source of energy and carbon in the form of polysaccharides, taken as glucose or fat decomposed by lipase, and absorbed mainly in the form of fatty acids (e.g. butyric acid), and glycerol. The issue of mushrooms’ demand for energy is not important in this article. Observations conducted during feeding tests show that incomplete meeting of the demand for energy in spawn during its enzymatic activity restricts the use of the substrate in the first two flushes. The constituents of cell membranes of straw are a major source of carbon and energy for mushrooms. It is composed of lignin, cellulose and hemicellulose. These components are available for mushrooms, because Mushroom is equipped with the enzymes that are taking part in their decomposition. These enzymes are referred to as Carbohydrate Active enzyme system (CAZyme). Lignin is primarily degraded during the vegetative growth of the spawn until placing of the casing soil with the participation of manganese peroxidase and laccase. By contrast, cellulose and hemicellulose are degraded after application of the casing soil by the cellulose. In mushrooms nutrition starch is mainly used as an intermediate element of decomposition of polysaccharides to glucose.
- Nitrogen in a mineral form – mainly in the form of ammonium ions to create amino acids, and in organic form to create endogenous amino acids from proteins; components of the cell sap and chitin responsible for supporting structure of fruiting bodies.
- other minerals, especially phosphorus, sulfur, potassium, magnesium, sodium, calcium, manganese. The role of calcium is of particular importance as it is regulating the pH of the substrate and casing soil and it has important effect on binding of fruiting bodies. Most micronutrients affect the process of feeding by enzymes in which they occur. One’s attention should be drawn to the special role of manganese.
- regulating substances (vitamins – especially biotin and aneurin, and growth substances).
The starting point in determining the nutritional needs of the mushrooms may be its composition. On average, it is assumed that the mushroom has 94 – 97% water, 2-4.3% protein and other organic compounds, including 0.2-0.7% of carbohydrate and 0, 05-1, 1% of mineral salts (mainly phosphorus, magnesium, potassium, calcium, iron) and microelements, vitamins and biologically active substances. Taking the highest indicated content of components in mushrooms, this means that with a yield of 40 kg/m2, it absorbs from a substrate and a casing soil: 36kg of water; the amount of nitrogen and amino acids needed to produce 1.7 kg of protein; glucose and other sugars to produce 2 kg of carbohydrates and to maintain vital functions; unsaturated fatty acids to produce 0.28 kg of fat; mineral salts – 0.44 kg.
The general diagram of nutrition is as follows:
Polysaccharides + enzymes of Mushroom →glucose (C6H1206) →respiration (O2) = 6CO2 + 6H2O + energy ↓
+ NH4+ = chitin (spawn and fruiting bodies)
In compost the source of dead cell walls are straw subjected to hot composting process (fiberisation and other) and cell walls of dead thermophilic organisms (mainly actinomycetes) multiplied in the process of maturation.
The mass of spawn depends on the activity of enzymes of mushrooms and the availability of dead organic matter created in Phase II compost. The highest activity of the enzymes takes place at a temperature of 250C. The concept of nutrition as a source of additional nutrients (feeding supplements) uses crafted caryopses of cereal and not protein supplements. The caryopses also contain protein. They – crafted caryopses of cereal introduced into the Phase III compost – are to: stabilize the quality as well as providing additional nutrients than those found in the substrate and also through the casing soil to achieve a specified level of yielding. Why cereals? Cereals are grasses and mushrooms in the wild grow in meadows (Mushroom campestris) and evolutionarily adapted to use the resulting humus formed on them in the composting process; mineralization which the dead grass undergoes. In addition, the caryopses of cereals contain all the ingredients necessary for diet of mushrooms.
The average composition of cereal seeds and soy is as follows::
Cereal seeds Soy
- Assimilative carbohydrates 60 -70% 3,4 – 4,5%
- Cellulose 1 -4% 3,5 – 4,5%
- Proteins 9-14% 45 – 48%
- Fats 5 -4.5% 2,0 – 3,5%
- Minerals 1,0 – 2,0%. 5,0 – 6,0%
The rest is water. Summary shows the basic differences in the carbohydrate content in favor of cereal seeds. These seeds also contain enough proteins, fats and minerals for the nutritional needs of mushrooms. These proportions are most similar to the composition of the Mushroom. It has needed enzymes to degrade components of the caryopsis of cereals, mainly carbohydrates of varying chain lengths consisting of glucose. The shorter the carbohydrate chains the easier the process of decomposition into glucose. Decomposition of cellulose is the hardest. This explains why we do not grow Mushroom on straw as is the case with Pleurotus.
Mushrooms are in much smaller quantities provided with enzymes degrading proteins or fats. Mushroom has considerable abilities to adapt the available enzymes to nutrients in the compost. This explains the usefulness of supplements made from cereal grains to feed the mushrooms by casing soil. In addition, the main source of nitrogen for the mushrooms is nitrogen in the form of NH4+, located in the substrate as a result of ammonification of proteins in the composting process.
The period of the biggest enzymatic activity of mushrooms’ spawn in the process of feeding starts after bringing the supplement to the substrate or the casing soil to the end of spawn’s growth after shock in conditions of access to water in these two environments. During this period, temperature of 250C and a high concentration of carbon dioxide and water access are expected in the compost and the casing soil.
Decomposition of compost by thermophilic organisms continues from the period of yielding of the first flush. It is their enzymes that decompose the compost; the mineralizing it provides Mushroom with additional components. It is illustrated on the diagram provided below:
Organic matter + O2 + aerobic microorganisms Þ
CO2 + NH4 + PO4 + biomass of microorganisms + thermal energy + humus
(After: Mieczysław BŁASZCZYK i Magdalena FIT, Sukcesja mikroorganizmów w czasie kompostowania odpadów organicznych [Succession of microorganism during composting of organic waste])
In case of mushrooms decomposed organic matter in the substrate is the one that was not decomposed by Mushroom and microorganisms are Scytalidium thermophilum. This process explains, among other, why the availability of water in the substrate increases during the third and subsequent flushes. This diagram explains also the way the protein supplements work, the increase in temperature and the increase in nitrogen content in the compost. This mechanism is also a cause of hyperactivity of compost; production of large amounts of heat, which makes it difficult to control the behavior of fruiting bodies; and the process of releasing pins in the second and subsequent flushes.
By mastering this process outside of compost, it would be possible in getting the supplement that would allow nourishing the mushrooms in the third flush.
An important novelty of the proposed approach for growing mushrooms is to expand the location where the feeding takes place on to the casing soil. Until now it was thought that it should be deprived of nutrients, as this can interfere with the binding process. Conducted research showed that the mushrooms using their enzymes decompose peat. It was the starting point for the introduction supplements from cereal grains into the casing soil. Initially it was thought that one will need to create double layered casing soil; separate for the nourishment and another one for binding. This proved to be unnecessary. The efficiency of nutrition process is due to two facts: first, there are no microorganisms in the casing soil, so they do not compete and do not consume, even partially, introduced nutrients, and second they are in the near distance from the pins and fruiting bodies. Why is this so important? Because the nutrients contained in the spawn must be transported to pins and fruiting bodies and incorporated into the forming cells and keeps them alive. They must also be accompanied by the transport of water. These two processes are undervalued in the cultivation of mushrooms. They explain many of today’s problems as causes of lower yields in the second flush, loss of quality from the middle of the first flush and also explain the high efficiency of feeding by a casing soil. Nutrients are transported through the mechanism of osmosis between living cells. Transport is relatively slow because it is about 2 cm per day. In contrast, soluble nutrients are transported in the process of water evaporation from the surface of the skin. They move in dead cells that make up a kind of „pipes”. This is practically the same mechanism as in plants. Please note that skin of mushrooms does not have stomata (defending itself against excessive evaporation by creating scales). This means that the transport of water depends on the water content in the air. When too much water evaporates, the deficit is too high which causes the fruiting body to become light and lose its shape. When it is too low or the evaporation is blocked, the fruiting bodies soaks up water excessively, the first sign is a ridge on the shaft, the mushrooms lose color, the fruiting bodies become pink or gray and stop growing. The same applies to pins. When this situation is maintained for a long term they burst and die.
Supplied nutrients are utilized in the increase in the number and mass of cells as long as there is a correlation between water transport and access to nutrients. The pace of transport and weight gain depends on the air temperature surrounding the pins, the fruiting bodies and the spawn during shock. This is often much higher than the air temperature measured by the sensors in the hall. This means that the shortage of water (water content) needed for the evaporation is sometimes (with the rapid growth of fruiting bodies, their high weight and increasing activity of the substrate) significantly different and considerably change over time. In case of disruption of evaporation mushrooms stop growing and fruiting bodies begin to prepare for the production of spores; they form a film under his hat and opens; entire supply of nutrients is used to produce and seeding spores. Mushroom receives a signal that its living conditions are bad and must therefore quickly produce spores, that seeding is its primary life goal. However, if conditions are good it tries to grow to maximum size, because it gives a chance to produce the greatest number of them.
Mushrooms in the subsequent flushes have to transport nutrients from the spawn that is increasingly distant from the surface of the casing soil. Transport is relatively slow. The acceleration by an increase in evaporation leads to a reduction in yield; fruiting bodies stop growing and open. It is therefore important to maintain the conditions providing transport and on the other hand, introducing supplement to casing soil to shorten the transport route. At first glance mushrooms have enough nutrients accumulated in the spawn located close to the fruiting bodies and those located in the casing soil can be used to increase the yield of a second flush. Nevertheless excessively rapid growth of fruiting bodies from the middle of the first flush may lead to a deficit of nutrients. This increase of evaporation is caused by excessive activity of the substrate.
As a side effect of the growth of mushrooms, heat, carbon dioxide and steam are emitted. In the controlled process one must take into account the need to remove them outside the cultivation hall. Otherwise, they distort the course of the expected behavior of mushrooms.