15A-22 |
Purification and characterization of phytases from Aspergillus niger var. awamori |
H. R. KIM1, T. S. Shin2, D. S. Byun1, J. H. Pyeun1, and J. S. Godber3. (1) Faculty of Food Science and Biotechnology, Pukyong National University, 599, Daeyen-Dong, Nam-Gu, Pusan, 608-737, South Korea, (2) Food Science and Nutrition, Yosu National University, 96-1, Dundeuk-Dong, Yosu-si, Chunnam, 550-749, South Korea, (3) Food Science, Louisiana State University and Agricultural Station, Food Science Bldg, Baton Rouge, LA LA 70803 Phytic acid is the major storage form of phosphate in plants, comprising 15% by weight of edible legumes, cereals, and oil seeds. Monogastric animals such as pigs and poultry lack or have low phytase activities in their digestive system and most undigested phytic acid is excreted in their manure. The presence of phytic acid in monogastric animal feeds works as an antinutritional factor, since the phosphate moieties of phytic acid chelate essential minerals and possibly bind to proteins making them unavailable for absorption. Another problem is the high levels of undigested phytic acid in the faecal waste that is discharged into sewage and becomes a cause of water pollution. Our objective was to establish a simplified purification method for two phytases from Aspergillus. niger var. awamori (ANA) and to characterize the properties of the phytases. Extracellular phytases produced by ANA were purified with ionic exchange column chromatography. Physicochemical and enzymatic properties of the phytases were characterized. Results showed that the molecular weights of the purified phytases, A and B, were estimated to be 84 and 74 kDa, respectively, by SDS-PAGE and 98 and 330 kDa using Superose 6 gel filtration. Phytase A showed maximum activity at pH 5.5 with a second activity peak occurring at pH 2.8 and maximum activity of phytase B was at pH 3.0. Optimum temperature of both enzymes was 65oC. Phytase A was stable to heat treatment at 65oC for 30 min; phytase B displayed considerably higher thermostability than either phytase A or a commercial phytase. These results suggest that phytases produced by ANA had a higher optimum temperature and a higher thermostability than the commercial phytase. Therefore, the phytases in this study have potential for commercialization in the feed industry.
Session 15A, Biotechnology
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