Phytase production using citric pulp and other residues of the agroindustry in SSF by fungal isolates

Abstract

Phytases have important applications in human and animal nutrition because they hydrolyze the phytate present in legumes, cereal grains and oil seeds. This results in an increased availability of minerals, trace elements and amino acids as well as phosphate. Fifty potential phytase-producing fungal strains were isolated from a fertile soil obtained from the northern part of Parana State in Brazil and other alternative sources using a selective media. Thereafter phytase production was evaluated in solid-state fermentation using different residues from the agroindustry supplemented with a nitrogen source at 60 % of moisture after 96 hours at 30 degrees C. The highest phytase activity (51.53 units per gram of dry substrate, U/g) was achieved with citric pulp and the soil isolate FS3 in solid-state fermentation. Furthermore, treatment of the substrates prior to fermentation in order to reduce microbial contamination was shown to affect phytase production during solid-state fermentation. Heat treatment resulted in an increase of the concentration of inorganic phosphate, a well known repressor of microbial phytase production, and therefore in a reduction of phytase production. UV exposure of the substrate was shown to reduce microbial contamination without affecting phytase production.