What are the causes of contamination in Lingzhi (Ganoderma) spawning?

1. Damage contamination

(1) Container damage: mechanical damage caused by failure to handle with care during filling, sterilization, inoculation, transport and cultivation.

(2) Air-pocket damage: rapid heating, pressure rise or rapid cooling during sterilization; excessive exhaust speed, causing bags to swell with air and rupture.

2. Cotton plug contamination

(1) Cotton plug contamination: the test tube mouth is stained with culture medium or the bottle (bag) mouth is not clean, or the culture medium comes into contact with the cotton plug.

(2) Cotton plug dampened: improper stacking during sterilization, too much water added, unreasonably built sterilization stove, or excessive moisture in the culture material, causing the cotton plug to absorb moisture and become contaminated.

3. Inoculation contamination

(1) The environment is not clean: the inoculation room is too large, not sealed, the inoculation room environment is not clean, and disinfection is not strict.

(2) Disinfection not strict: the inoculation box is not airtight, disinfection is not thorough, or the clean bench was not switched on in advance as required before inoculation, and the inoculation tools and the operator's hands were not disinfected or not strictly disinfected.

(3) Poor aseptic awareness: not following aseptic operating procedures, with lax requirements.

4. Stock culture carrying bacteria

(1) Infrequent inspection: during the cultivation of mother cultures and stock cultures, regular inspection and removal of contaminants was not carried out, and contaminating bacteria were covered by mycelium and thus not discovered.

(2) Lax work: when transferring tubes or expanding mother cultures, they were used immediately without careful inspection, and contaminated cultures were mistakenly used.

5. Mixing contamination

(1) Uneven mixing: during mixing, the culture material was not fully stirred evenly, cottonseed hulls were not fully pre-wetted, carried granular material or insufficient moisture, causing some parts to be too dry and forming sterilization dead corners.

(2) Raw materials carrying bacteria: moldy, non-fresh raw materials were used during mixing, causing the raw materials themselves to carry large amounts of contaminating bacteria.

6. Sterilization contamination

(1) Incomplete sterilization: insufficient time or insufficient humidity in atmospheric-pressure sterilization; failure to exhaust cold air in high-pressure sterilization, causing false pressure or pressure gauge failure.

(2) Stacked too tightly: when loading the pot, the items were stacked too tightly, affecting steam penetration and producing dead corners.

(3) Serious air leakage: due to air leakage in the sterilization pot, the required temperature cannot be reached.

7. Cultivation contamination

(1) Damp environment: the relative humidity of the cultivation room is too high, exceeding 70%, which favors the growth of contaminating bacteria and causes the cotton plugs to absorb moisture and become contaminated.

(2) Cotton plug too loose: the cotton plug is made too loose, and contaminating bacteria in the air enter through the gap.

(3) Dirty site: the cultivation room is not clean, the density of contaminating bacteria in the air is high, and the site is not regularly sterilized and disinfected.

(4) Damage by insects and rodents: rats gnaw the cotton plugs or culture bags and bring in contaminating bacteria. Or pests such as mites and grain beetles breed in the culture medium.