Researchers from Embrapa Eastern Amazon and from Embrapa Agroenergy have found an alternative to produce edible mushrooms such as Pleurotus ostreatus, or oyster agaric, in Brazil at a low cost, and thus make its consumption accessible to most of the population. The scientists used residual biomass, waste generated in the processing of palm oil, as substratum to cultivate the fungus. According to researcher Marcos Enê Oliveira, the oyster agaric finds ideal conditions to develop in the industrial oil palm residue produced in Brazil, especially in Pará, where the industry generates three tons of solid waste and a ton of liquid effluents. Oliveira explains that the residual biomass is fibers and substances that are rich in protein, lipids, carbohydrates and minerals, which can nourish edible mushrooms such as oyster agaric, also known as oyster mushroom, a product that is quite appreciated in the national and international cuisine. Currently, few can afford to buy oyster agaric in the Brazilian market. The kilo of the product costs between R$ 48.00 and R$ 80.00 because most of it comes from abroad and thus has a high cost of import. The freight alone accounts for about two Reals of the price per kilo. Moreover, it requires a lot of care in the transportation and the conservation of the product. Versatile mushrooms The researcher underscores that cultivating such edible mushrooms is possible due to their versatility in growing under different weather conditions and substrata. “This fungus has an enormous capacity to break lignocellulosic fibers, which are considered chemically complex, and extract the nutrients it requires to grow and fructify from them”, the specialist reports, explaining that the crop imitates what occurs in the nature by supplying plant residue in a substratum formed by fibers and by the effluent generated. To get to the ideal mix, the Embrapa Agroenergy researchers Félix Siqueira and Simone Mendonça tested substratum formulas with different concentrations of residue, including boiler ash, which also derives from oil palm processing. The substratum is sterilized in an industrial autoclave to be inoculated with the fungus later. The colonization stage, which is the growth of the fungus in the substratum, takes around 25 to 30 days in a darkroom that mimics nature, where the mushrooms grow protected from the light in the duff or on tree logs. Oyster agaric production in palm oil industry waste Rich effluent The liquid that flows out of oil palm processing, which is known by the acronym Pome (palm oil mill effluent), mainly comprises water, minerals and organic matter, and it is currently destined to waste stabilization ponds, as per legislation. “Some experiences have pointed to using the effluent to fertilize oil palm crops, but such application is still being studied to ensure that it does not have environmental impact”, the researcher Félix Siqueira clarifies. Valuable oil palm waste The Brazilian state of Pará accounts for over 90% of the Brazilian production of African oil palm. In 2017, for example, the state produced about 480,000 tons of this oil, generating approximately 1.4 million tons of solid and liquid waste. According to Roberto Yokoyama, director of the company Dendê do Pará (Denpasa) and chairman of the Oil Palm Trade Chamber, the average cost of the ton of crude oil produced in Brazil is around US$ 610 to US$ 650, and the investment required to set up a mill is about a million Reais for each ton of processed bunches, and at least 30% of this amount is directly related to the waste. In the oil processing industry, waste includes the empty bunch; the effluent (Pome); the fruit fiber and the rind, (resulting from pressing); the muddy sediment, solid particles generated in the separation between the oil and the water; and palm kernel, residue from pressing the almond. Yokoyama reports that some of them are already used for other purposes, such as animal feed and generation of energy, but the volume produced is still large. “Even though there are some uses, the waste generated is still a problem for the industry”, he affirms. In numbers, each ton of fresh fruit bunches (FFB) that goes into the agroindustry, are produces an average 220 kg of empty bunches, 120 kg of pressed fiber, 50 kg of rind, 20 kg of palm kernel, 60 kg of muddy sediment and between 650 kg and 1,000 kg of effluent. Such residue are basically composed of cellulose and lignin, a complex fibrous material, whose links can be broken by Pleurotus fungi. Mushrooms have promising market In 2017, Brazil imported nearly 12,000 tons of mushrooms and truffles as dry, preserved or prepared goods, according to data by the Brazilian Ministry of Agriculture, Livestock and Food Supply (Mapa). And the national production of fresh mushrooms totals around 12,000 tons a year, according to the National Mushroom Growers' Association (ANPC). Domestic consumption, according to the association, is small because of a lack of culinary tradition, with emphasis on white mushrooms (Agaricus bisporus), shiitake (Lentinula edodes) and oyster mushrooms (Pleurotus). The largest oyster agaric growers in Brazil are located in the state of São Paulo. In addition, Félix Siqueira, a researcher from Embrapa Agroenergy, stresses that there is enormous potential for the production of regional Amazon edible mushrooms that are already aclimated to forest conditions. “Tropical forests are some of the largest mushroom biodiversity banks and there are many with food and nutraceutical potential (bioactive substances that benefit health)”, the scientist underscores. “Nexto to lignocellulosic remains, we have observed many mushroom species growing naturally, which may be domesticated and conquer a clientele”, he believes. Mushroom waste as fish feed Even the waste generated by mushroom production can generate valuable bioproducts, explains the researcher Félix Siqueira, from Embrapa Agroenergy. After the Pleurotus mushroom cultivation and harves, the researchers used their residual biomass to prepare fish feed. The plant biomass that remains after the mushroom harvest is rich in nutrients both from the plant and from the fungal mass, an important characteristic to compose fish feed formulas. The researcher observed that the post-harvest biomass showed enough digestibility for market insertion as fish feed. The first tests with tambacu (a tambaqui and pacu hybrid) fry have offered positive results. "The fry fed with oil palm biomass after the mushroom cultivation have shown similar or better digestibility when compared to those fed with commercial formulas”, Siqueira reports. He explains that that is only the first step in the continuity of the research, and that preliminary results give opportunities for discussion with palm oil agroindustries to establish permanent research focused on microbial fermentation bioproducts (i.e. from macrofungi that form mushrooms). “It is an alternative to minimize the sector's environmental impact, following the model of biorefinaries”, he suggests. He stresses that in the context of the bioeconomy, this constitutes "zero waste" production, a cycle of sustainability in which waste is raw material for new products. Translation: Mariana Medeiros