Produtividade do cogumelo Lentinula edodes em função de linhagens, substrato de cultivo, compostagem e tratamento térmico

Abstract

The cultivation of Shiitake mushrooms in axenic system has been predominant and provided by specialized companies. The purchase of this substrate is impracticable for many regions owning to its high transportation cost and also, the production of the substrate itself requires an investment level normally inaccessible for small-scale producers. In this context, two alternatives deserve to be considered: a) severe pasteurization of the substrate and b) short composting followed by severe pasteurization. First, the severe pasteurization of the substrate was evaluated, which was compared with the combination severe pasteurization/autoclaving and only autoclaving, with different times of treatment. Afterwards, the composting process was evaluated with different formulations, composting time, and the strain effect. Due to the number of experiments, the tests were conducted, at first, in small vats with a capacity of 15 kg and at the end, an experiment was conducted on a larger scale with 100 kg of substrate (dry weight) to simulate the conditions on a normal scale of composting. In this experiment, the composting was conducted for 8 days, however, with an evaluation of the process with 4, 6 and 8 days of composting. For each of these times of composting, the blocks were submitted to different heat treatments: a) 12-hour severe pasteurization at 80°C, b) 1-hour autoclaving, c) 2- hour autoclaving, d) 3-hour autoclaving. All blocks were inoculated with 2% of shiitake inoculum. After inoculation, the blocks were incubated until complete colonization and brown film formation in a room at ambient temperature. For fruiting, the blocks were transferred to a cultivation chamber with 90%±5 humidity and a temperature of 18 to 20°C. The severe pasteurization of the non-composted substrate was efficient only after 24 hours. The 4-day composting followed by pasteurization can be done as long as the pasteurization time occurs for 36 hours in a row. Shorter pasteurization times resulted in high levels of contamination. Substrates based on sugarcane bagasse + sawdust, and only sawdust, composted for 6 days and pasteurized for 12 hours, showed zero contamination and rapid mycelial growth. The LECAR strain was the most productive on substrates based on composted sawdust and wheat bran. Data referring to composting with different levels of rice bran showed that the best productivity results were obtained in treatments between 15 and 20% of rice bran. Still, the same experiment realized with cornmeal resulted in low mushroom production with the chosen levels. The experiment with coffee and soybean rusk did not reach a mushroom production stage, because the composting process did not result in good quality substrate. Also, abnormal browning and an unpleasant odor were observed, unlike the other experiments. These results showed that the use of soybean meal or coffee husk associated with the use of composting could only be possible at levels below those tested here or in a combination with another roughage instead of sawdust.