Faculty of Food Technology and Biotechnology, University of Zagreb
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 Paraná 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 °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.Fitaze imaju važnu ulogu u prehrani ljudi i životinja jer hidroliziraju fitate leguminoza, zrnja žitarica i sjemenki uljarica, pa tako povećavaju pristupačnost minerala, elemenata u tragovima, aminokiselina i fosfata. Iz plodnog tla sjevernog dijela brazilske države Paraná, a i iz drugih izvora, na selektivnim podlogama izolirano je 50 sojeva gljiva koje mogu proizvesti fitaze. Nakon toga je proizvodnja fitaze ispitana uzgojem na čvrstoj podlozi od raznih ostataka agroindustrije, uz dodatak izvora dušika, pri 60 %-tnoj vlažnosti i 30 °C tijekom 96 sati. Najveća aktivnost fitaze (51,53 U/g suhe tvari) dobivena je uzgojem izolata FS3 iz tla na pulpi citrusa. Obrada supstrata prije procesa, radi smanjenja onečišćenja mikroorganizmima, utjecala je na proizvodnju fitaze. Toplinskom obradom povećala se koncentracija anorganskog fosfata, koji suzbija mikrobiološku proizvodnju fitaze. Izloženost supstrata UV-zrakama smanjuje onečišćenje mikroorganizmima, a pritom ne utječe na proizvodnju fitaze
