Holocellulase from filamentous fungi grown in culture media containing cassava wastewater

Cultivation of cassava is a widely adopted practice in Brazil and aims to produce food source with high starch content from cassava root. Its industrial processing generate solid and liquid wastes, such as the toxic cassava wastewater (CW) containing hydrocyanic acid, which is stored in stabilization ponds. There are some alternatives to the use of CW in order to treat or reduce its toxicity. Understanding the microbial ecology present in the decomposition of CW is needed to exploit its biotechnological potential. This work aimed to select holocellulases-producing filamentous fungi from decomposing CW and cultivate them in submerged fermentation of CW alone and CW plus banana stalk (BS). Enzymatic activities were determined using the method of dinitrosalicylic acid. Characterization and partial purification of enzymes were performed by molecular exclusion and ion exchange chromatography. Culture medium formulations containing CW exhibited cellulases activities (FPase, Endoglucanase and exoglucanase), hemicellulase (xylanase and mannanase) as well as for pectinases and amylases. One of the fungal isolates was identified as Aspergillus niger, which showed galactomannanase activity in CW alone of 0.180 UI.mL^-1, while for CW with BS it was up to 0.480 UI.mL^-1. It is possible to consider CW as nutrient source for the production of holocelulases of filamentous fungi, especially when added a complex lignocellulosic carbon source. As an extension of this work, it is in progress the analysis of the microbial ecology capable of inhabiting the cassava wastewater using metagenomic techniques in order to characterize, isolate and investigate microorganisms in the decomposition of this residue.