Precautions for Mushroom Production and Methods for Preventing Aspergillus

Mushrooms are a type of natural food that is rich in color, fresh, fragrant and crisp, delicious, nutritionally balanced, and also has therapeutic value, and is deeply loved by people. However, during the mushroom cultivation process, Aspergillus contamination can occur, and after being affected, loose granular substances in different colors such as yellow, black, and gray-green can be seen. Aspergillus is widely distributed in nature, and conidia float and spread with air currents. So what should be noted during the mushroom production process? How can Aspergillus in mushrooms be prevented?

1. What should be noted during the mushroom production process?

1. The ambient temperature for culturing spawn must not exceed 28°C. In addition, cultured spawn should not be stored at room temperature for more than half a month.

2. Thoroughly master the spawning time and temperature of the culture medium to prevent the destruction of nutrients, and the pH should be suitable.

3. The culture medium should be changed frequently; for example, culture medium materials such as peptone, wheat bran, and potato should be used alternately.

4. The stock culture should not be used up all at once; it should be taken in portions, and the remainder should be stored at low temperature to prevent too many subcultures.

5. Each year, one tissue isolation should be carried out by selecting fruiting bodies that are large, grow normally, and are robust and free of pests and diseases, from which the superior are selected and the inferior removed to expand inoculation and growth.

2. How can Aspergillus in mushrooms be prevented?

1. Damage symptoms

After contamination by Aspergillus, loose granular substances in different colors such as yellow, gray-green, and black can be seen with the naked eye, varying by type. Aspergillus can also cause mold in grain and other materials, as well as mildew and deterioration in industrial materials such as leather, textiles, and optical glass.

2. Morphological characteristics

The hyphae are septate, colorless, pale, or with colored substances condensed on the surface. The conidiophores grow upright and unbranched, and the tip of the stalk swells into a spherical or club-shaped vesicle, whose surface is covered with radiating sterigmata, with conidia borne in chains at the tips of the sterigmata. The conidia are single-celled, spherical, ovoid, or elliptical, and the spores are yellow, green, brown, black, and various other colors. Colony color varies among different species.

3. Occurrence pattern

Aspergillus is widely distributed in nature and can survive on all organic materials such as soil, grain, and plant materials, and its conidia float and spread with air currents. The optimum temperature for the growth of Aspergillus flavus is 25-30°C, and the relative air humidity is about 80%; the suitable temperature for Aspergillus niger is 20-30°C, and the relative air humidity is above 85%; Aspergillus glaucus has strong drought tolerance, and a temperature of 20-35°C and relative air humidity of 65%-80% are most suitable for its growth. In mushroom cultivation, environmental conditions such as relatively high water content in the compost, excessively high relative air humidity, and poor ventilation are favorable for Aspergillus growth and cause contamination and harm to mushrooms.

4. Control methods

Pay attention to good environmental sanitation, keep the area around the culture room and the cultivation site clean, and deal with waste materials in a timely manner. The inoculation room and mushroom house must be cleaned and disinfected according to regulations; during spawn production, operators must ensure thorough sterilization, and bagged spawn must be handled gently during transport and other processes to strictly prevent plastic bags from breaking; inspect frequently, and promptly remove contaminated spawn when found, and never sow diseased spawn. If Aspergillus occurs on the compost of the mushroom bed, ventilate and dry it promptly, control the room temperature at 20-22°C, and resume routine management after the contaminating microorganisms are suppressed. Adjust the pH, appropriately raise the pH, and adding 1%-3% quicklime when mixing materials or spraying 2% limewater can inhibit the growth of contaminating microorganisms. For chemical mixing into the material, mixing with thiophanate-methyl at 0.1% of the dry material weight gives a better control effect. In addition, when filling spawn bottles, do not overfill them to avoid the cotton plug touching the material; after filling the bottles, wash the bottle mouths clean and keep the cotton plugs clean.