GENE CLONING, PURIFICATION, AND CHARACTERIZATION OF A HEAT-STABLE PHYTASE FROM THE FUNGUS ASPERGILLUS-FUMIGATUS

The finding of heat-stable enzymes or the engineering of moderately th ermostable enzymes into more stable ones by random or site-directed mu tagenesis has become a main priority of modern biotechnology. We repor t here for the first time a heat-stable phytase able to withstand temp eratures up to 100 degrees C over a period of 20 min, with a loss of o nly 10% of the initial enzymatic activity. The gene (phyA) encoding th is heat-stable enzyme has been cloned from Aspergillus fumigatus and o verexpressed in Aspergillus niger. The enzyme showed high activity wit h 4-nitrophenyl phosphate at a pH range of 3 to 5 and with phytic acid at a pH range of 2.5 to 7.5.