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Dynamic sterilization

Equipment developed by Fungibras stimulates the mushroom-growing process.

miguel boyayan Shiitake with open cap: perfect time for harvestingmiguel boyayan

Edible mushrooms, which are low-fat and full of proteins, vitamins, and carbohydrates, have gradually attracted more and more consumers in Brazil. Nonetheless, consumption in Brazil corresponds to 30 grams per person, which is light years away from the two kilos that the French consume and the eight kilos that the Chinese consume. Price is certainly one of the obstacles to the expansion of the mushroom market; mushrooms are expensive to produce because of the complex cultivation. Preparation of the substrate, comprised of sawdust and cereal grains that have to be carefully sterilized to avoid future contamination by other fungi and bacteria, is one of the steps of this process when the mushrooms are cultivated in acclimatized cultivation chambers (with controlled temperatures, humidity and aeration). An innovative, dynamic sterilization system designed by researcher Augusto Ferreira Eira, a retired professor from the School of Agronomy Sciences of Paulista State University/Unesp, was developed at Fungibras, a company from the city of Botucatu, in São Paulo State.

Instead of the traditional autoclaves – equipment that uses high pressure water steam – in which the substrate is placed in small polypropylene plastic bags to be sterilized at 120º Celsius, Eira designed a cylindrical 2.5 meter-high machine that revolves horizontally, with the capacity to store 1.5 tons of the substrate at the same time. The sterilizer was developed with the help of FAPESP by means of the Innovative Research in Small Businesses/PIPE program. “As this equipment is dynamic, the mass constantly comes into contact with the hot steam; that is, the entire substrate is sterilized,” says Eira. “In the autoclave, the process is static, so it takes two hours to sterilize the outer part of the substrate and it can take several hours to sterilize the inside, especially in the case of bags with large amounts of the substrate”

A big screw in the format of a helicoid worm gear, is placed in the center of the equipment. This allows for the substrate to be taken out of the sterilizer when it is ready, and to prepare it, after cooling off, to inoculate the mushrooms. These procedures are done through a hatchway, without any external contact; therefore, there is no risk that the material will be contaminated. It takes roughly three hours to heat the 1.5 tons of mass, the same amount of time it takes for the mass to cool off. The two cycles are concluded in six hours at most. “To sterilize the same quantity in the autoclave, it would be necessary to have five machines with a volume of 10 thousand liters each,” he compares. That is, more time and energy is necessary to produce the steam.

The development of the dynamic sterilizer is a result of the researcher’s academic background. With a degree in agronomy, Eira dedicated himself to microbiology ever since the beginning of his professional career, when he was still a trainee on a scholarship, in 1965. His interest in fungi resulted in the creation of the Mushroom Module at Unesp’s School of Agronomy Sciences in 1985, and in a theme project funded by FAPESP, the objective of which was to study cultivation technology, biochemical characterization and the protective effects of edible and medicinal mushrooms (read more in nº 100 of Pesquisa FAPESP).

miguel boyayan Block of shiitake in acclimatized cultivation chambermiguel boyayan

Family-owned concern
In 2004, after he retired, Eira created Fungibras with his sons, Guilherme and Frederico Castilho da Eira, who are both agronomy engineers. “Before beginning the project, I conducted a survey on patented sterilization equipment available around the world and discovered some machines that are trying to do the same thing, but function in an entirely different manner,” says professor Augusto. “None of those machines carry out all the operations – homogenization, sterilization, cooling, inoculation and extrusion of the substrate – in a single unit.” The construction details included in all these operations are part of the patent request.

A prototype of the sterilizer was built during the first phase of the project. Tests showed that the researchers were going in the right direction. The machine currently being used at Fungibras was built during the second phase of the project. This machine is being used to produce substrate by using the axenic method – which means the culture is free of contaminating organisms, as it goes through a sterilization process that prevents the appearance of pests and diseases until the fructification phase – and to produce mushroom matrixes (seeds). These matrixes stem from tiny thin filaments called mycelium or hyphae, removed from the mushroom cap.

The substrate comes out of the sterilizer by a door that opens inside a sterilized laboratory. To produce the seeds, the desired quantity of mycelium is placed in the prepared substrate. Then the inoculated mass is placed in acclimatized sheds and the mushrooms are ready to be picked after 50 to 60 days. This method is quite different from the technique used in the wild, which is still used in some regions in Brazil. In this technique, the mycelium is inoculated directly into tree trunks or into compound and pasteurized substrates. As this is a very primitive technique, the first mushroom harvest from inoculated logs can take from six months to a year after the seeds are sown. Axenic cultivation in sterile substrate allows the mushrooms to grow freely in a medium with more nutrients, balanced pH and controlled humidity. Fungibras is already cultivating shiitake (Lentinula edodes) and shimeji (Pleurotus ostreatus) mushrooms in acclimated cultivation chambers, as well as mycelium seeds for various mushrooms, including the mushroom of the sun (Agaricus blazei) to meet producers’ orders.

The company, whose activities began when it was an incubator company at the Business Development Center of Botucatu, has grown and, since September 2006, its facilities are located in a three-thousand square meter lot in the city’s Industrial District. Research work with the dynamic sterilizer has not been concluded yet. “We’re only going to start thinking about actually maximizing the use of the equipment, with a marketing strategy, when all the mushroom production variables are defined,” says Eira.

fungibras Mushroom of the sun at various stages of maturityfungibras

“Scientific literature mentions approximately 2 thousand species of edible mushrooms,” reports researcher Arailde Urben, from Embrapa Recursos Genéticos e Biotecnologia, in Brasília, one of the 41 units of the Empresa Brasileira de Pesquisa Agropecuária. Of all these species, only 10 have become commercially popular. Although there is no official data available on the quantity of mushrooms produced in Brazil, because sales are often made directly by the producer to the consumer, especially to restaurants and hotel chains, estimates are that approximately 8 thousand tons of mushrooms – champignons, mushrooms of the sun, shimeji and shiitake – were produced in 2004.

Favorable climate
Brazilian producers are concentrated mostly in the Southeast and the South. The region of Mogi das Cruzes, in São Paulo State, has a big Japanese community and accounts for 70% of the production of edible mushrooms in Brazil. “The climate in this region – mild temperatures and high humidity – is favorable for the cultivation of mushrooms,” explains agronomy engineer Augusto Abdo, coordinator of agribusiness at the Rural Trade Union in Mogi das Cruzes. The ideal conditions for the cultivation of mushrooms are also found in the Alto Tietê region, which includes, in addition to Mogi das Cruzes, the towns of Salesópolis, Biritiba Mirim and Suzano.

Embrapa Recursos Genéticos e Biotecnologia has a mushroom germplasm bank with 321 species, of both edible and medicinal interest. The bank was started by means of collecting native species in several Brazilian regions and includes some non-native species. “When we find species with good therapeutic potential, we ask a biochemist to analyze them,” says Arailde. In the last few years, a number of research studies by Brazilian, Japanese and American researchers were conducted to test the alleged therapeutic effects of mushrooms, especially the mushrooms of the sun. “They are being studied as possible allies in the complementary treatment of diseases such as cancer, lupus, human papilomavirus /HPV and AIDS,” says Arailde, who is keeping track of these studies. There is no consensus among researchers as to the actual protective effects of these species. What researchers do know is that the mushrooms are an excellent nutritional complement.

Tropical Cultivation

A Chinese technique for the cultivation of mushrooms, which resorts to grass as the main raw material of the compound, has been disseminated in Brazil by Embrapa Recursos Genéticose e Biotecnologia. “Called Jun-Cao (literally translated as grass-like fungus), the technique uses dehydrated grass, ground into tiny two to three-centimeter fragments, mixed with rice and wheat flour,” explains researcher Arailde Urben. Agricultural gypsum is used to neutralize the pH of the compound; the gypsum functions as a binding element for the grain and sawdust particles.  The material can be sterilized in a commercial pressure cooker, in an autoclave or by means of pasteurization.

“The Jun-Cao technique was developed by the Chinese in 1983 and, in a period of four years, China was able to increase its production by 250%,” says the researcher, who has a degree in Biology and is specialized in fungi. In 1995, she participated in the first international course to publicize the method in developing countries. “This technique prevents trees from being cut down, grass is much cheaper than logs and cultivation time corresponds to approximately 40 days.” This issue will be addressed at the 4th International Symposium on Mushrooms in Brazil, to be held in the city of Caxias do Sul, in the State of Rio Grande do Sul, from October 27 to October 30.

The Project
Process for multiple sterilization, homogenization, inoculation and bagging operations, with the objective of producing inoculants and substrates for the cultivation of edible and medicinal mushrooms (nº 03/13014-8); Modality Innovative Research at Small Businesses/Pipe; Coordinator Augusto Ferreira da Eira – Fungibras; Investment R$ 371.058,87