Tratamento da torta de semente de algodão por autoclavagem e macrofungos para degradação de gossipol

Abstract

Cotton seed cake (TCA, in Portuguese) is a coproduct obtained after the extraction of cottonseed oil, which has been used as one of the raw materials for biodiesel production. TCA is restricted for animal nutrition, being more used for ruminants, due to the high concentration of the antinutritional and toxic factor, gossypol. The objective of the present study was to evaluate the ability of some macrofungi species to degrade free gossypol using TCA as substrates after being sterilized by autoclaving process. Thirty-five macrofungi were evaluated for their growth capacity in medium containing TCA and reduction of free gossypol (GL, in Portuguese). Thirteen macrofungus presented mycelial growth capacity in culture media containing TCA+Agar (Petri plates) or only in TCA (glass bottles) as nutritional source. Six macrofungus with best growth performance were selected and evaluated for GL degradation capacity during solid state fermentation (FES, in Portuguese) system.The humid heat sterilization (autoclaving) of the TCA showed significant degradation of free gossypol, however, there were still considerable levels of residual GL in the biomass. The six macrofungus presented capacity to reduce up to 90% of the residual value of GL in autoclaved TCA. Pleurotus ostreatus CC389 was chosen from among the six macrofungus to determination of biological efficiency and productivity of edible mushrooms. It was also analyzed the enzymatic activities and degradation of GL in post-harvested mushroom biomass (SMS, Spent Mushroom Substrate). P. ostreatus CC389, when cultured in TCA as a substrate for 20 days, secreted lignolytic enzymes such as laccase (up to 166.67 IU/mL) and manganese peroxidase (up to 12.81 IU/mL). It also degraded the residual GL by up to 94% at the end of the cultivation period. The activity of manganese peroxidase showed correlation with the degradation of GL. Mushroom productivity of P. ostreatus CC389 was approximately 20% in four different substrate formulations based on TCA (70%) mixed with 30% of different lignocellulosic biomass sources. The biological efficiency was higher when P. ostreatus CC389 was cultured in substrate containing TCA and eucalyptus sawdust (up to 67%). The SMS and the mushrooms obtained at the end of the P. ostreatus CC389 cultivation in the different formulations presented reduction of GL up to 99%. The results obtained with P. ostreatus CC 389 assays for degradation of GL in TCA and when enriched with other lignocellulosic biomass sources could represent an interesting link for the integration of biofuels (biodiesel), fungiculture (edible mushrooms) and animal nutrition (inputs - enzymes, bioactive molecules, nutritional sources - crude protein) production chains.