Abstract
Phosphate-solubilizing microorganisms were isolated from soil around Kyungnam and Kyungbook regions using potato dextrose agar-calcium phosphate medium. A fungus with the greatest phosphate-solubilizing activity was selected and identified to Aspergillus sp. PS-104, based on the morphological characteristics of conidiophore and conidia; unbranching type of conidiophore, terminally swelling of conidiophore and septate of mycelium, in malt extract agar and potato dextrose agar media. The optimum temperature and initial pH to solubilize rock phosphate in potato dextrose broth-rock phosphate medium were $30^{\circ}C$ and pH 7.0, respectively. In these optimum conditions, phosphate-solubilizing activities of Aspergillus sp. PS-104 against four twos of insoluble phosphate, tricalcium phosphate, aluminium phosphate, hydroxyapatite and rock phosphate, were quantitatively determined. As result, the maximum phosphate-solubilizing activity was obtained with tricalcium-phosphate (1,900 ppm) while minimum activity was obtained with hydroxyapatite (320 ppm). Futhermore, phosphate-solubilizing activity of Aspergillus sp. PS-104 was found higher when treated with nitrates as compared to the ammonium salts as a nitrogen sources.
PDA-calcium phosphate 평판배지를 이용하여 경상남북도 일대의 토양으로부터 인산가용화능이 우수한 사상균을 분리하고 배양특성을 조사하였다. 최종적으로 분리한 인산가용화능이 우수한 사상균 PS-104 균주를 선발하여 형태적 특성을 조사한 결과 이 균주의 분생자는 비가지형으로 끝이 돌출되어 있으며, 균사가 격막으로 형성되는 등의 특징을 갖는 Aspergillus sp. PS-104 균주로 동정되었다. 이 균주의 인광석 분해능이 최대가 되는 최적 배양온도와 pH는 각각 $30^{\circ}C$와 pH 7.0이었다. 이와 같은 배양조건에서 tricalcium phosphate, aluminium phosphate, hydroxyapatite, 인광석 등의 난용성 인산염에 대한 이 균주의 인산가용화능을 살펴보면 최대 인산가용화능은 tricalcium-phosphate 처리구(1,900 ppm)에서, 최소 인산가용화능은 hydroxyapatite 처리구(320 ppm)에서 확인되었다. 또한 이 균주의 인산가용화능은 질소원으로 첨가한 ammonium 염보다 nitrate 염에서 높게 나타났다.
