Mushroom Preservation Protocol

Why We Need Mushroom to become Preserved?

• Frequent loss of texture-softening.

• Protein and carbohydrate contents are decreased.

• Formation of brown coloration.

• Depletion of soluble compounds.

• To use in the future in different areas (like for biotechnological, pathological, taxonomical environmental, ecological and industrial, systematic and biodiversity applications or studies).Currently, there is a growing interest in obtaining and studying the biologically active compounds from higher Basidiomycetes.

• To solve morphological change and to minimize the risk of contamination.

• For further maintenance, characterization, and identification of culture, to tackle anthropogenic and natural influence that affect species diversity or abundance.

• To sustain food security and safety because it is quickly spoiled.

• For many years genetic stability, distribution, and commercialization.

• Forever increasing human population and diminishing farm sizes have resulted in declining soil fertility associated land productivity and increasing poverty levels.

• Combating malnutrition, generating income, accessing and benefit sharing.

• Creating new dimensions of sustainable agriculture and forestry (bio-innovations) [10].

Factors Affecting Preservation

Several factors affect the effectiveness of the preservation process: lack of good laboratory practice and viability test, strain type or quality, selection of temperature, composition of the growth and preserve media, time storage, and concentration of cryo- conservation/freeze-drying protecting agent (like glycerol, dimethyl sulfoxide, bovine albumin serum, skimmed milk, ethylene glycolsorbitol, and trehalose or myo-inositol). Few microorganisms can survive after the preservation process without a protecting agent; these agents can provide a longer storage time, avoiding cellular injuries [11, 12]. However, it attacked by pathogens and pests dominantly. Therefore, the storage of microbial cultures is difficult and time-consuming. In order to guarantee viability for these microorganisms, various procedures have been carried out allowing the management of strains. In another word, evaluation of conservational methods and strain viability must be performed always.

Short and Long-Term Types of Mushroom Preservation Techniques

Each species needs compatible and distinctive alternative techniques for their active, pure and viable physiology in terms of color, texture, and taste. Preservation protocols are applied to store cultures in viable and stable form for long periods without losing genotypic, phenotypic and physiological traits. Some of them listed below. 1. Continuous sub-culturing but it has its own limitation at all. Several studies demonstrated that storage of fungi by sub-culturing may induce antigenic changes, phenotypic and genetic alterations as well as attenuation of virulence. Sub-culturing was used conventionally for regular activity. In most cases, it leading to the problems of contamination and degeneration. It is difficult for storing large numbers of fungal cultures. It is time-consuming. Then, it does not prevent genetic and physiological changes.

2. Inoculation of mycelia in malt extract agar then store in sterile distilled water at +4oC [13]. The most common method of short-term storage of mushroom culture is storing the culture tubes at room temperature (28- 35ºC) for a period of 1-2 months or in refrigerator (5– 8ºC) for an average period of 3-4 months.

3. Lyophilization and cryopreservation (freezing at -80°C

and storage in liquid nitrogen [-196°C]).

Cryoprotectants are of two types: penetrating agents such as glycerol and dimethyl sulfoxide (DMSO), which readily pass through the cell membrane and protect intracellularly and extracellularly, and non-penetrating agents such as sucrose, lactose, glucose, mannitol, sorbitol, dextran, polyvinyl-pyrrolidone, and hydroxyethyl starch, which exert their protective effect external to the cell membrane. Cryopreservation is a process where cells or whole tissues are preserved by cooling to low sub-zero temperatures by adding cryoprotectants which act as antifreeze by lowering the freezing temperature and increasing the viscosity. Cryopreservation of cultures is considered as the most acceptable method of preservation.

4. At +4°C and 20oC indifferent concentration of glycerol by using two different methods (slant culture and slice cut method) with Agar plug components [14].

5. Inoculation of the spawn on a sterilized substrate (seeds).Cereal grains (hard endosperm wheat, medium hard endosperm wheat or hard endosperm rye) plus malt extract agar at -70ºC or 4oC. The use of glycerol as a cryoprotective solution at -70ºC. Over the years, researchers have developed practical, effective, and ingenious methods of preserving fungi or mushroom on various organic substrate such as wood chips, cereal grains, straw, filter paper, insect and plant tissues [10, 14, 15].

6. Potassium sorbate (0.1%) and citric acid (4%)

extended the shelf life of mushroom for 24 days [16].

7. 30% brine solution. At a temperature range become

25-300c for 6 up to 7 days [17].

8. Drying Techniques it includes low heat air blow (LHAB,

Anjaad TM), sun drying (SD) and gas laboratory oven (LO) drying, solar dryer, vibro dryer, vacuum dryer, and hot air oven. Drying seems to be an effective approach to extend shelf life. This is widely reported worldwide [18, 19].