Abstract
This study was carried out to measure insoluble phosphorus fractions content fixed in different soil type and isolate a superior phosphate solublizing bacteria(PSB) producing free phosphate in citrus orchard soil. Distribution of insoluble phosphate fraction ordered Al-P>Ca-P>Fe-P in the investigated citrus orchards. Insoluble phosphate fraction such as Al-P, Ca-P, Fe-P were higher in volcanic ash than in non-volcanic ash soil. A PSB with high holo zone in PDA-P medium isolated from citrus orchard soil. This strain identificated by MIDI system as Bacillus sphaericus. The optimum growth of pH and temperature were at 4~5, $30^{\circ}C$, respectively. When Bacillus sphaericus cultured at $25^{\circ}C$, 150 rpm condition in LB broth medium included different phosphate. Bacillus sphaericus produced free phosphate in the culture broth medium from tricalcium-phosphate(207.0 ppm), aluminium phosphate(324.5 ppm) and hydroxyapatite(334.8 ppm) and Phosphatase activity of Bacillus sphaericus was higher at $35^{\circ}C$ culture condition than that of $25^{\circ}C$. Two type preparation inoculated Bacillus sphaericus made with carrier materials such as Bentonite, $CaCO_3$, Sodium alginate. Density of PSB in this preparation conserved at $10^5c.f.u.\;g^{-1}$ level during storage in different temperature condition for 7 month. It also showed that free phosphate produced at PDA-P medium.
본 연구는 감귤원 토양유형별로 고정되어 있는 난용성 인산염함량을 파악하고 이를 생물학적으로 이용하고자 인산가용화 우수미생물을 선발하여 특성을 조사하였다. 토양중 난용성 인산염의 형태별 분포는 Al-P>Ca-P>Fe-P 순으로 화산회토 토양이 비화산회토 보다 많았다. PDA-P배지를 이용하여 인산염 가용화능이 우수한 Bacillus sphaericus를 분리하였으며 pH 4~5와 $30^{\circ}C$에서 생육이 제일 좋았다. Bacillus sphaericus은 $AlPO_4$에서 324.5 ppm, $Ca_{10}(PO_4)_6(OH)_2$에서 334.8 ppm, $Ca_3(PO_4)_2$에서 207.0 ppm의 유리인산을 생성하였으며 인산효소활성은 $35^{\circ}C$에서 배양할 때 높았다. Bacillus sphaericus를 Bentonite 등 담체에 고정 후 온도를 달리하여 7개월 보존기간 동안 밀도변화를 조사한 결과 $10^5c.f.u.\;g^{-1}$ 수준과 인산가용화능을 유지하여 추후 생물비료로 이용이 가능할 것으로 기대된다.
