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. 2005 Dec;33(4):223-9.
doi: 10.4489/MYCO.2005.33.4.223. Epub 2005 Dec 31.

Culture Conditions and Characterizations of a New Phytase-Producing Fungal Isolate, Aspergillus sp. L117

Dae-Hee Lee  1 , Sun-Uk Choi, Yong-Il Hwang
Affiliations

Culture Conditions and Characterizations of a New Phytase-Producing Fungal Isolate, Aspergillus sp. L117

Dae-Hee Lee et al. Mycobiology. 2005 Dec.

Abstract

A novel fungal strain Aspergillus sp. L117 that produced acid-stable and thermostable phytase was isolated on basis of the clearing zone on PSM plate and the ability of Na-phytate hydrolysis. The phytase of isolate showed a 3-fold higher activity than that of A. ficuun NRRL3135. The Aspergillus sp. L117 produced maximal level of phytase at initial pH of 5.0 and 30℃. The optimal pH and temperature for phytase activity were 5.5 and 50℃, respectively. The phytase showed totally stable activity after 20 min of exposure between 30 and 90℃, and even at 100℃. The highest level of residual phytase activity was obtained at pH 5.5, and still retained the stability at the broadest pH ranges (2.0 to 7.0) of all the aforementioned phytases. Storage stability of phytase was preserved over 96% of initial activities for 60 days at 4, -20, and -70℃ and to retain even 70% of the initial activity at room temperature.

Keywords: Acid-stable and thermostable phytase; Aspergillus sp.; Phosphatase.

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Figures

Fig. 1
Fig. 1
The effect of counterstaining assay on the clearing zone formed by the fungal strain L117 phytase (A) and morphological appearance of Aspergillus sp. L117 (B).
Fig. 2
Fig. 2
Time course of phytase peoduction by Aspergillus sp. L117 in starch medium at initial pH 6.8 at 30℃, 180 rpm.
Fig. 3
Fig. 3
Effect of initial pHs or culture temperatures on the production of phytase, phosphatase, and biomass of Aspergillus sp. L117. The strain was cultured in 100 ml of nutrient medium at different pHs (between 2.0 and 7.0) and temperatures (between 30 and 90℃) for 5 days. Error bars show S.E. of estimated parameters.
Fig. 4
Fig. 4
Effect of pHs or temperatures on the activity of Aspergillus sp. L117 phytase. Error bars show S.E. of estimated parameters.
Fig. 5
Fig. 5
pH stability and thermostability of Aspergillus sp. L117 phytase after exposure for 20 min to the indicated temperature or pH. Error bars show S.E. of estimated parameters.
Fig. 6
Fig. 6
Storage stability of phytase solution.
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