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Microbial phytases, especially from fungal and bacterial sources, have received much attention as food additives in human nutrition and as feed supplements for monogastric animals. An effective expression screening method for recombinant production of this enzyme on a small scale is industrially desirable. An effort has been made in this work to clone and express phytase genes from Aspergillus sp. and Escherichia coli with the selected host, vector and inducer combination. Albeit the formation of insoluble inclusion bodies by fungal phytase, recombinant E. coli appA was effectively expressed in a cost-effective manner in the periplasm of BL21plysS using an inducer concentration of 0.01 mM in 4 h of growth. Enzyme was purified in three consecutive steps and functional studies were carried out., Mikrobne fitaze, osobito iz plijesni i bakterija, imaju vrlo važnu ulogu u prehrambenoj industriji kao aditivi i dodaci prehrani monogastričnih životinja. Za industrijsku je proizvodnju poželjno pronaći učinkoviti postupak ekspresije gena za dobivanje rekombinantnih fitaza. U radu je prikazan postupak kloniranja i ekspresije gena za proizvodnju fitaza iz plijesni vrste Aspergillus i bakterije Escherichia coli, s pomoću pažljivo odabrane kombinacije domaćina, vektora i induktora. Iako su pritom nastali netopljivi agregati (tzv. inkluzije), rekombinantni gen E. coli appA uspješno je i bez većih troškova izražen u periplazmi stanica BL21plysS, uz koncentraciju induktora od 0,01 mM, tijekom 4 sata rasta. Enzim je pročišćen u tri uzastopna koraka, te su ispitane njegove značajke.