compound formed during seed maturation [12]. The seed of J. curcas has a high concentration of phytic acid, up to 10% of its dry matter [2]. Tannins are polyphenols water-soluble and polar solvents [13]. The tannin content in the seeds of J. curcas is low, representing only 3% of its dry weight [13].Detoxification of the Jatropha seed cake could allow its use as a protein-rich dietary supplement in the animal feed [1,14,15].The use of residue or by-products in animal nutrition can minimize expenditures on the development of food sources, such as soybean, cotton and wheat meals, without causing undesirable effects on the overall production system. However, it is first necessary to know the nutritional value and effects of the by-product's inclusion in animal diets.Some studies have used physical and chemical treatments to detoxify Jatropha seed [2,16,17]. These methods have been effective but require the use of chemicals that may result in other the presence of other residues. Conversely, bio-detoxification does not require the application of any chemical compounds. It may also reduce the concentrations of phorbol esters and anti-nutritional factors to non-toxic levels [18].
Methodology
Microorganism, fungal growth conditions and inoculum production (spawn)The isolate Plo 6 of P. ostreatus used in this study belongs to a culture collection from the Department of Microbiology at the Federal University of Viçosa, MG, Brazil. P. ostreatus was grown in a Petri dish containing potato dextrose agar culture medium at pH 5.8 and incubated at 25 °C. After seven days, the mycelium was used for inoculum production (spawn) in a substrate made of rice grains [19]. The rice was cooked for 30 min in water with a ratio of 1:3 rice: water (w/w). After cooking, the rice was drained and supplemented with 0.35% CaCO 3 and 0.01% CaSO 4 . Seventy grams of rice was packed into small glass jars and sterilized in an autoclave at 121 ºC for 1 h. After cooling, each jar was inoculated with 4 agar discs (each 5 mm in diameter) containing the mycelium. The jars were then incubated in the dark at room temperature for 15 d.
Substrate and inoculationThe J. curcas seed cake was obtained from an industry of biodiesel (Fuserman Biocombustíveis, Barbacena, Minas Gerais State, Brazil).To select the most suitable substrates for lignocellulolytic enzyme production, we conducted preliminary experiments with Jatropha seed cake and various lignocellulosic residues. We tested P. ostreatus growing on Jatropha seed cake with different percentages of eucalyptus sawdust, eucalyptus bark, corncobs, and coffee husks [20]. The addition of these agroindustrial residues was necessary to balance the carbon and nitrogen ratio, which might benefit mycelial growth [21][22][23].
