OK, now lets move from tomatoes to mushrooms :). Tissue culture is one of the applications of biotechnology that is widely used in mushroom cultivation. It is also called as the agar culture. The tissue of the fungal organism called mycelium is used in this method to grow mushrooms. The traditional way of growing mushrooms that deals with compost and spores are time consuming.
Tissue culture of mushrooms
The process of tissue culture is laborious and needs to be carefully studied under excellent lab conditions. The process is usually divided into three steps and are as follows:
• First step deals with formation of the spawn using the tissue culture method. Most of the times, saw dust or sterilized grains are used as the ground medium to develop spawns.
• The secondary stage deals with the fungal organism ‘mycelium’ and is introduced into the developed spawn.
• The acquired spawn is then introduced into an organic material to support the formation of the mushroom. This organic material is called as the substrate. The substrate used in the tissue culture method supports the actual growth of mushrooms.
Kinds of Mushroom
Mushrooms are broadly classified into two types based on the environment, namely the compost and the other that grows on the woody material. The common and the most popular type of mushroom known as the ‘Aquarius bisporus’ is grown using the compost method. Other mushroom types such as Oyster mushrooms, shiitake, reishi, maitake, and Lions Mane prefer woody environment. It is very difficult to specify the number of species of mushrooms present throughout the world. Some species of mushrooms are edible, while others are poisonous. The identification of edible mushrooms can be done through careful microscopic observations.
Nutrients in Mushroom
Mushrooms are an excellent source of vitamin B and essential minerals that helps in reducing high cholesterol levels and increases immunity. Potassium content in the mushrooms helps in reducing the blood pressure and in turn prevents strokes. The mineral selenium in the mushroom can act against free radicals preventing cell damage and other related effects. The mineral selenium is found more in animal proteins, so for a vegetarian diet this can provide the same benefits. Mushrooms also contain the mineral copper which is necessary for the normal growth of the body. The nutrition value of the mushrooms may differ for certain species but most edible mushrooms species grown in farms are good for health and even have medicinal values.
Mushroom growing can be done in three ways based on the environment we choose. It can be growing in farms or using existing environments such as growing in woods and logs. Growing it on the woods and logs will be more like growing in a natural environment.
• For growing a particular species of a mushroom, understanding the choice of wood, harvesting methods and the suitable conditions are more important.
• This method of growing mushrooms in wood and logs as a growing medium needs some expertise and careful study. So it is better to choose farming methods which are now very popular and also the easiest of all the methods.
• By growing mushrooms in farms it is possible to provide the necessary conditions such as temperature and moisture.
The mushroom farming usually comprises of six steps which are necessary for the mushroom production. These six steps include preparing the compost, secondly finishing the compost, thirdly spawning, fourthly casing, fifthly pinning and finally cropping.
Step 1: Making the compost
Compost preparation is the first step in growing mushrooms. Compost is done with ingredients that supply essential nutrients needed for the growth of a mushroom. Preparing compost can be done in two ways. Using horse manure along with nitrogen and gypsum forms compost and is the cheapest way compared to synthetic composts which uses hay and crushed corncobs. Preparing compost involves mixing and arranging the ingredients in a rectangular pile. The initial phase includes arranging of rectangular layers of ingredients with tight sides and loose centers. A compost turner is used to mix the synthetic compost or horse manure along with nitrogen and gypsum. Then water is sprayed at regular intervals to maintain the moisture content. Now leaving the compost for 7 to 14 days in a suitable temperature of about 155° will create some chemical reactions in the presence of ammonia.
Step 2: Finishing the compost
The second step involves in reducing the ammonia content in the compost and pasteurization. The content of ammonia in the compost will be very high after the first step. Excess ammonia content in the compost will not favor the growth of mushroom in the spawn. The ammonia content in the compost is reduced to 0.07 percent. Pasteurization is the process that helps in removing or neutralizing harmful species from the compost.
Step 3: Spawning
The addition of the fungal organism mycelium to an organic material will help in initiating the growth of the mycelium. The organic material is nothing but a substrate which acts as a growing medium.
• Choosing the right substrate for the right type of mushroom is important.
• Generally materials like logs, wood dust and straw are used as substrates.
• Using sterilized grain also help in forming spawn.
In the spawning process, the sterilized grains are mixed with water and chalk. Then the mixture is added to the compost along with a bit of mycelium in regular intervals. After mixing the compost, a temperature of 75° should be maintained. This temperature will help in maintaining the moisture content of the compost. This process of growing mycelium in the organic material for about 14 to 21 days is called spawning. Maintaining the ideal temperature and moisture content at the final stages of the spawning will maintain the mycelia growth. The rate of spawning varies based on the weight of the spawn and compost and by maintaining the temperature; it is possible to reduce the time taken for spawning.
Step 4: Casing
After making the spawn it should be packed in such a way that supports mushroom growth. This process is called casing and it is done using clay loam field soil, ground limestone along with a mixture of peat moss. This casing allows the formation of rhizomorphs inside the compost which is responsible for the mushroom growth. After casing there is a possibility of harmful species and pathogens to develop inside the casing. With the help of pasteurization it is possible to eliminate these harmful species. The moisture content inside the casing is the key to mushroom growth. Maintaining the moisture by spraying water at regular intervals is important. The next factor to be considered is the temperature of the casing. For the initial period of casing the temperature should not increase more than 75°.
Step 5: Pinning
After casing is done, one can find the sprouts of initial mushroom grown over the rhizomorphs. They are extremely small but can be seen as outgrowths on the compost. Once the mushroom grows four times its initial size, they are called pins. Then the pin starts to expand and becomes larger after a particular period. After casing and the initial growth of pin, it will take around 18 to 21 days for the mushroom to develop completely. With the 0.8 percent of decrease in the carbon dioxide level, the pinning normally develops. Exposure to fresh air in the atmosphere will help in reducing the carbon dioxide content. By reducing the effect of pinning, the quality of the mushroom will increase considerably. It also helps in reducing the number of days to start harvesting.
Step 6: Cropping
Cropping is the final step involved in mushroom cultivation. This cropping process will take 3 to 5 days in the harvest period. Cropping is done in a periodic manner in the harvesting days. The mushrooms will start to form after the cropping period. Harvesting days varies based on the mushroom type and other related conditions. It may range from 35 to 42 days and in some cases the harvest can reach up to 150 days.
Temperature and moisture level plays an important role in each stage. In this final stage of cropping, a temperature of 57° to 62° should be maintained throughout the cycle. Maintaining the temperature will benefit us in many ways. It reduces the effect of harmful species and pathogens that can develop in the final stage and also helps in yielding better results. After completing the production cycle, it is important to protect the mushroom growing area from pathogens and pests. Pasteurization will stop spreading these harmful species to the next production cycle. The total yield depends on the temperature, humidity, most importantly pests and so on.