Purification and Characterization of Extracellular Phytase from Bacillus licheniformis Isolated from Fish Gut

Abstract

The phytase producing bacterial strain, Bacillus licheniformis ONF2 was isolated from the proximal intestine of the freshwater fish, Nile tilapia, Oreochromis niloticus. The bacterial phytase was purified 37.45 fold from the crude supernatant by two step chromatography with an overall yield of 21.3 %. It was a monomeric protein with molecular mass of 40–42 kDa. The enzyme was optimally active at pH 6.5–7.5 and at 50 °C temperature and was quite stable at pH ranging from 5.0 to 9.5. It showed temperature stability range of 20–75 °C. The activity of the enzyme was moderately inhibited by 5 mM Mn2+, Mg2+ and K+ and largely affected by the metal ions Cu2+, Hg2+, Zn2+, Co2+ and EDTA but, in the presence of 1 mM CaCl2, the inhibitory effect was less intense. One unit of purified phytase released 1130.3 ± 40.2 and 720.5 ± 35.2 µg of inorganic phosphate per gram of sesame seed meal and soybean meal respectively. The properties of the presently purified phytase to hydrolyze plant phytate and maintaining stability at high temperature make it suitable for applications in animal feed industry.