Abstract
The phytase from Mitsuokella jalaludinii, a novel phytase-producing rumen bacterium, was purified 120-fold to near homogeneity and characterized. The phytase was completely cell-associated and about half of the enzyme activity was released when the bacterial cells were incubated with 1.5 mol/l KCl solution for 8 h. The optimum pH for phytase activity was in the range of 4.0 to 5.0 and the optimum temperature was 55 to 60°C. The phytase was stable at pH 4.0 to 7.0. It was highly specific to sodium phytate as the substrate, strongly inhibited by Cu2+, Zn2+, Fe2+and Fe3+, significantly stimulated by Ba2+ and slightly stimulated by Mn2+ and Ca2+. The metal ions chelating agents, namely trisodium citrate, potassium sodium tartrate and EDTA, did not show any inhibitory effect on the phytase activity of M. jalaludinii. The phytase was also not inhibited by sulfhydryl inhibitor, 2-mercaptoethanol, and a carboxyl inhibitor, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDAC). Key words: Mitsuokella jalaludinii, bacterial phytase, rumen bacteria.
Highlights
Phytases, which catalyze the hydrolysis of phytate into inorganic phosphate, inositol and inositol mono- to pentaphosphates, appertain to the family of histidine acid phosphatases (Pasamontes et al, 1997)
Phytases have been reported to be present in several bacterial species such as Pseudomonas spp. (Richardson and Hadobas, 1997), Enterobacter sp. (Yoon et al, 1996), Klebsiella aerogenes (Tambe et al, 1994), Klebsiella terrigena (Greiner et al, 1997), Klebsiella pneumonia (Sajidan et al, 2004), Escherichia coli (Greiner et al, 1993), Bacillus subtilis (Powar and Jagannathan, 1982; Shimizu, 1992; Kerovuo et al, 1998), Citrobacter braakii (Kim et al, 2003) and
The optimum temperatures of phytase for most micro-organisms are in the range of 50 to 70°C
Summary
Phytases, which catalyze the hydrolysis of phytate into inorganic phosphate, inositol and inositol mono- to pentaphosphates, appertain to the family of histidine acid phosphatases (Pasamontes et al, 1997). Phytases have been reported to be present in several bacterial species such as Pseudomonas spp. (Yoon et al, 1996), Klebsiella aerogenes (Tambe et al, 1994), Klebsiella terrigena (Greiner et al, 1997), Klebsiella pneumonia (Sajidan et al, 2004), Escherichia coli (Greiner et al, 1993), Bacillus subtilis (Powar and Jagannathan, 1982; Shimizu, 1992; Kerovuo et al, 1998), Citrobacter braakii (Kim et al, 2003) and Lactobacillus amylovorus (Sreeramulu et al, 1996). The best characterized phytase, so far, is that from Aspergillus ficuum. The phytase from A. ficuum NRRL 3135 was found to be a combination of activities from an acid phosphatase and an 85 kDa glycosylated protein with a preference for phytate as a substrate (Ullah, 1988). Of the bacterial phytases studied, only phytases from Enterobacter sp. (Yoon et al, 1996), B. subtilis (Powar and Jagannathan, 1982), B. amyloliquefaciens (Ha et al, 1999) and L. amylovorus (Sreeramulu et al, 1996) are extracellular while the others are cell-bound (Greiner et al, 1993; Tambe et al, 1994; Jareonkitmongkol et al, 1997; Yanke et al, 1999)
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