92 h, water content of 50.72% and temperature of 28.85 °C. SSF is a technology that can propose alternative paths for

the reuse of agro-industrial waste, therefore decreasing possible environmental problems, as well as adding economic value to these co-products. The authors are thankful to the National Council for Scientific and Technological Development (CNPq) for granting the ITI (Industrial Technology Initiation) scholarship, and the Northeast PD0332991 Brazil Bank (BNB) for granting financial support. “
“Proteases comprise the class of enzymes most used worldwide, accounting for 60% of the world’s total enzyme production (Gupta, Beg, & Larenz, 2002). This is due to the diversity of applications that these proteins, mainly alkaline proteases, have in various industries, e.g. food, detergents, pharmaceuticals (Espósito et al., 2009a and Klomklao et al., 2005). Several studies report that fish viscera can be used as an important source of GW3965 alkaline proteases (Bezerra et al., 2005, Khantaphant and Benjakul, 2010, Klomklao et al., 2009a and Souza et al., 2007). These residues, which are usually discarded, represent a significant source of these enzymes. The use of alkaline proteases from aquatic organisms, especially trypsin, has markedly increased in recent years, since some proteases are stable and active under harsh conditions (high temperature

and pH) and in the presence of surfactants or oxidising agents (Espósito et al., 2009b and Klomklao et al., 2005). Furthermore, the recovery of proteolytic enzymes from fish viscera represents an interesting alternative

when the aim is to minimise the economic losses and ecological hazards caused by this waste (Bougatef et al., 2007 and Souza et al., 2007). Trypsin (EC 3.4.21.4) is one of the most studied fish digestive proteases. This enzyme belongs to the serinoproteases family and is responsible for many biological processes, e.g. protein digestion itself, MRIP zymogen activation and mediation between the ingestion of food and assimilation of nutrients (Klomklao, Benjakul, Visessanguan, Kishimura, & Simpson, 2007). Trypsins have been extracted, purified and characterised from the viscera of various commercial fish, such as Oreochromis niloticus ( Bezerra et al., 2005), Katsuwonus pelamis ( Klomklao et al., 2009a) and Lutjanus vitta ( Khantaphant & Benjakul, 2010). Tropical regions are home to a large diversity of fish species with distinct feeding habits, which explain the differences among enzyme compositions of these organisms. The carnivorous fish, pirarucu (Arapaima gigas), is considered the largest freshwater fish in the world, reaching over 200 kg in weight and up to three metres in length, whose geographic distribution area predominantly covers the Amazon basin ( Nelson, 1994). A. gigas is considered a species of considerable commercial interest, and is one of the most highly priced species in the Brazilian fish market.