A two-phase solid-state fermentation process for mushroom (Agaricus bisporus) production on cereal grains

Grain-based substrates subjected to a two-stage solid-state fermentation (SSF) process for Agaricus bisporus mushroom production were tested as alternatives to the environmentally problematic compost-based substrate. Scytalidium thermophilum, the dominant thermophilic fungal species found in compost-based substrates, was used in the primary stage of the SSF process to pre-treat grain-based substrates, which was followed by inoculation with A. bisporus in the secondary stage. The objective of this study was to determine the effect of the two-stage SSF process on the substrate colonization period and mushroom productivity for A. bisporus and substrate bioefficiency using various grain-based substrates. To this end, three sterilized substrates composed of grain (rye, millet, and oat) and other minor ingredients were used as the basal nutrient substrates. The first experiment varied the incubation duration (0, 10, and 20 days) with S. thermophilum at 46°C and grain type in the primary stage of the SSF process. The results indicated that incubation period, but not grain type, had a significant effect on mushroom yield and substrate bioefficiency (p < 0.05). Yield decreased significantly beyond the 10-day incubation period with S. thermophilum compared to that of the control treatment without S. thermophilum. Use of shorter primary stages with S. thermophilum (0, 2, 4, and 6 days) suggested that both incubation duration and the interaction of grain type and incubation duration were significant for mushroom yield and substrate bioefficiency (p < 0.05). The substrate colonization periods for A. bisporus using substrates pre-colonized by S. thermophilum were shorter (22 to 23 days) when compared to control treatments (44 to 50 days) without S. thermophilum pretreatment (p < 0.05). In conclusion, when using grainbased substrates for mushroom production, the addition of S. thermophilum in the primary stage of the SSF process shortened the time for substrate colonization by A. bisporus in the secondary stage. Further, the two-stage SSF process described herein increased mushroom yield when using an oat grain-based substrate.