1 Valorization of agro-industrial wastes to produce hydrolytic enzymes by fungal solid state fermentation C. Marzo*, A.B. Díaz, I. Caro and A. Blandino Department of Chemical Engineering and Food Technology, Faculty of Sciences, International Agro- Food Campus of Excellence (CeiA3), IVAGRO, University of Cádiz, Pol. Río San Pedro s/n, Puerto Real, Spain * Corresponding author: cristina.marzo@uca.es Keywords: Enzymes, Solid state fermentation, Agro-industrial residues, Hydrolysis Abstract Purpose: The aim of this work was to produce hydrolytic enzyme cocktails derived from the fungal solid-state fermentation (SSF) of two different agro-industrial residues: orange peels (ORA) and exhausted sugar beet cossettes (ESBC). These cocktails were used to hydrolyse the residues in order to convert them into fermentable sugars. Their effectiveness compared to commercial enzymes was also studied. Methods: SSF was carried out on ORA and ESBC for a few days and xylanase, pectinase (exo- polygalacturonase), cellulase and -glucosidase activities were measured on the extracts obtained. Enzymatic hydrolysis of ORA, ESBC and the solid waste obtained after orange peels SSF were carried out by using different enzymes cocktails, analysing resulting reducing sugars. Results: High xylanase and pectinase titers were measured on enzymatic extracts from both wastes; being the production higher on ESBC. With regard to the enzymatic hydrolysis of the solid residues, the highest reducing sugar yields were obtained when commercial cellulase was supplemented with the enzymatic extracts obtained in this work by SSF. Conclusions: ORA and ESBC are adequate substrates for the production of hydrolytic enzyme by SSF. The produced enzymatic extracts might be used as supplement of commercial cellulase in order to hydrolyse lignocellulosic residues, increasing significantly the reducing sugars yield. 1. Introduction A large number of agro-industrial wastes and by-products, such as exhausted sugar beet cossettes (ESBC), orange peels (ORA), grape pomace or rice husk, are produced by agricultural and agro-food industries. Frequently, these wastes are discarded, however, they can be used to produce a wide range of high-added value by-products such as ethanol, enzymes or biologically active secondary metabolites [1]. In this way, the bioprocessing of these wastes, which are economic and have great availability, can help to solve environmental problems associated with their disposal and, moreover, they can be used as raw materials to obtain high-added value by- products [2]. Different processes have been studied in order to find a more efficient utilization of these materials, being the solid-state fermentation (SSF) an interesting alternative. In fact, it turns out to be a promising technology for waste valorisation, that have been proved to be very efficient in terms of product yields and productivities, low energy consumption, and solving disposal problems [3]. Solid-state fermentation is a three-phase heterogeneous fermentation (solid-liquid-gas), in which solid particles represent the main phase. The majority of the water in the system is absorbed within the moist solid-particles. In this technique, microorganisms grow on the surface of a porous solid substrate with enough moisture to maintain microbial growth and metabolism.