Valorization of Residual Agroindustrial Cakes by Fungal Production of Multienzyme Complexes and Their Use in Cold Hydrolysis of Raw Starch

In this work four agroindustrial cakes were used as raw material both for production of enzyme pools containing amylases and accessory hydrolases by solid-state fermentation (SSF) and for cold starch hydrolysis. Eight fungal strains from the genera Aspergillus and Penicillium were screened for enzyme production, and their enzyme extracts were then evaluated in the hydrolysis of raw cakes. Babassu cake was the most suitable raw material for endoamylases, exoamylases and proteases production. The highest activities of these three enzymes were produced by A. awamori IOC-3914 (29.8 U g(-1)), A. wentii (47.8 U g(-1)) and P. verrucosum (27.5 U g(-1)), respectively. Regarding cellulases and xylanases, maximum activities (12.8 and 598.0 U g(-1), respectively) were obtained by A. awamori IOC-3915 in castor seed residue. Saccharification studies showed a flexible applicability of the raw extracts to hydrolyze different cakes. A maximum total reducing sugars concentration of 13.9 g L-1 was obtained from babassu cake using a raw enzyme extract produced by A. awamori IOC-3915, without any concentration or purification steps. The present results demonstrate that a low-cost SSF process can supply enzyme extracts with a high potential for application in the cold hydrolysis of raw starch from agroindustrial cakes.