Overview of secondary fermentation of white button mushroom compost 

Overview of secondary fermentation of white button mushroom compost 

The primary fermentation material is evenly moved into the secondary fermentation tunnel, and the culture material is precisely fermented through temperature control. After the temperature equalization period, temperature rise period, pasteurization, temperature reduction and temperature control fermentation, the culture material is finally softened, the harmful bacteria and eggs in the culture material are killed, a large number of beneficial microorganisms and actinomycetes are produced, and the ammonium nitrogen is converted into organic nitrogen. The ammonia in the pile is removed to prepare a secondary fermentation culture material suitable for the growth of Agaricus bisporus mycelium.

2. Secondary fermentation stages and purposes

(1) Temperature equalization period:

① The temperature of the primary material just filled into the secondary fermentation tunnel is relatively high, and the material temperature in different parts varies greatly. It is necessary to use high wind speed to equalize the temperature and pull the pile temperature to the same starting point for regulation.

② Due to the influence of high temperature and high ammonia, the microbial activity of the primary fermentation material is relatively low. During the temperature equalization period, the material temperature is generally set at 47~48℃ to accumulate and expand the microorganisms, accumulate microorganisms for the rapid start of pasteurization, and avoid the difficulty of removing ammonia due to the low amount of actinomycete microorganisms.

③ The temperature equalization period usually takes 6 to 36 hours, and the length of time depends on the maturity of the pile, the amount of ammonium nitrogen, and the microbial activity of the pile.
Usually, if the pile is not mature enough, the temperature equalization time can be extended; the ammonium nitrogen in the pile is 0.6% as the dividing line, and if it is higher than this index, the temperature equalization time should be relatively extended; for materials with low microbial activity, the temperature equalization time should also be extended.

(2) Heating period: When the temperature difference in the pile is less than 3°C, and the heat generation of the pile is stable and no longer changes dramatically, it means that the temperature equalization can be ended and the temperature increase can be started. The temperature increase is usually set to increase from 48°C to 57°C at a rate of about 1.5°C. When the air inlet temperature at the bottom of the pile exceeds 56°C and the pile temperature reaches 57°C, the temperature increase is completed and pasteurization begins.

(4) Cooling: After pasteurization, the temperature should be quickly cooled, ventilation and oxygen should be provided, and the material temperature should be cooled from 56~60℃ to about 48℃. This process usually takes about 4 hours.

(5) Temperature control and fermentation:

① The pile after pasteurization basically does not contain miscellaneous bacteria, but there are still a small amount of thermophilic microorganisms, actinomycetes and other beneficial bacteria. At this time, attention should be paid to cultivating and expanding the number of beneficial bacteria. The growth temperature range of beneficial bacteria that can remove ammonia is between 46~49℃, which is a small temperature range and very sensitive. When the temperature is higher than 49℃, microorganisms are easy to regenerate ammonia. When the temperature is lower than 46℃, the microbial activity is low and the ammonia removal is very slow.
② In the early stage of the temperature control period, because the microbial activity is relatively low, the main focus should be on heat preservation. The material temperature should be kept as high as possible (48~49℃) and ventilation should be carried out in small amounts. After one day, when the microorganisms gradually increase by orders of magnitude, a large amount of heat will be generated and a large amount of oxygen will be required. At this time, the material temperature should be kept low (about 47℃) and ventilation should be carried out in large amounts.
③ The massive growth of beneficial microorganisms will utilize ammonia and further decompose the pile, accumulating a large amount of microbial protein for mushroom mycelium.

(6) Cooling and sowing: After the temperature control and decomposition are completed, the pile does not contain ammonia and presents a soft but not rotten structural characteristic. At this time, the temperature should be immediately lowered to about 26℃ for sowing. If the ammonia has been removed but the temperature is not lowered, the actinomycetes will further decompose the pile, which is likely to cause the pile structure to deteriorate.

3. Secondary fermentation material indicators
Moisture 66%~69%, pH7.2~7.7, ash content less than 30%, nitrogen content 1.8%~2.1%, no ammonia, fluffy structure, soft but not rotten pile, and a large number of actinomycetes can be seen.