• KSBB Journal
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• v.13 no.5
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• pp.497-501
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• 1998

A fungus with high phosphate solubilizing activites was isolated from soil using potato dextrose agar-calcium phosphate medium and identified to Penicillium sp. PS-113, based on the morphological characteristics of conidiophore and conidia; flask shape of phialide, simple branching type of conidiophore, and columnar shape of conidial head, in malt extract agar and potato dextrose agar media. The optimum temperature ad initial pH to solubilize rock phosphate in potato dextrose broth-rock phosphate medium were 30$^{\circ}C$ and pH 8.0, respectively. In these conditions phosphate solubilizing activities of Penicillium sp. PS-113 against four types of insoluble phosphate like tricalcium-phosphate, aluminium phosphate, hydroxyapatite and rock phosphate were quantitatively determined. As results, this fungus highly produced free phosphates to the culture broth with the concentrations of 1,283 ppm against tricalcium-phosphate, 585 ppm against rock phosphate, 528 ppm against aluminium phosphate, and 242 ppm against hydroxyapatite, respectively.

• Korean Journal of Environmental Agriculture
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• v.26 no.1
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• pp.36-41
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• 2007

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.

• Journal of Life Science
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• v.23 no.2
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• pp.242-248
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• 2013

The objective of this study was to develop a mineral phosphate-solubilizing bacterium as a biofertilizer. A mineral phosphate-solubilizing bacterium HR-1019 was isolated from cultivated soils. It was identified as Bacillus subtilis by 16S rDNA analysis. The phosphate-solubilizing activities of the HR-1019 strain against three types of insoluble phosphate, hydroxyapatite, tri-calcium phosphate, and aluminum phosphate were quantitatively determined. When 5% of glucose concentration was used as a carbon source, the strain showed marked mineral phosphate-solubilizing activity. Mineral phosphate solubilization was directly related to pH drop in the culture solution of the strain. The pathogenic activity and antifungal effects of the HR-1019 strain were measured inclear zones formed in PDA media.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.94.2-95
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• 2003

E. intermedium 60-2G possessing a strong ability to solubilize insoluble phosphate, has plant growth-promoting activity, induced systemic resistance activity against scab pathogen in cucumber, and antifungal activity against various phytopathogenic fungi. The phosphate solubilizing activity of 60-2G may be mainly accomplished by production of gluconic acid through a direct extracellular oxidation of glucose by glucose dehydrogenase that required a PQQ cofactor for its activation. A pqq gene cluster conferred Phosphate-solubilizing activity in E. coli DH5${\alpha}$ was cloned and sequenced. The 6,783 bP pqq sequence had six open reading frames (from A to F) and showed 50-95％ homology to pqq genes from other bacteria. The E. coli strain expressing the pqq genes solubilized phosphate from hydroxyapatite after a pH drop to 4.0, which paralleled in time the secretion of gluconic acid. To study the role of PQQ in biocontrol traits of E. intermedium, PQQ mutants of 60-2G were constructed by marker exchangee mutagenesis. The PQQ mutants of E. intermedium were lost activities of solubilizing phosphate, growth inhibition of phytopathogenic fungi, and plant growth promotion. These findings suggest that PQQ plays an important role, possibly activation of certain enzymes, in several beneficial bacterial traits of E. intermedium by as yet an unknown mechanism.

• Journal of Life Science
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• v.11 no.2
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• pp.63-69
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• 2001

bacterium having high abilities to solubilize in-organic phosphate was isolated from cultivated soils. The strain was identified as Aeromonas hydrophila DA33, based on the physiological and biochemical properties. The optimum temperature and initial pH to solubilize insoluble phosphate in sucrose minimal medium were 3$0^{\circ}C$ and pH 5.0, respectively. In these conditions, phosphate-solubilizing activities of the strain against two types of insoluble phosphate were quantitatively determined. When glucose was used for carborn source, the strain had a marked mineral phospahte solubilizing activity. Inorganic phospahte solubilization was directly related to the pH drop by the strain. Analysis of the culture medium confirmed the production of gluconic acid as the main organic acid released by Aeromonas hydrophila DA33.

• Korean Journal of Agricultural Science
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• v.49 no.3
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• pp.463-481
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• 2022

Phosphorous (P) is considered to be one of the key essential elements demanded by crop plants. Approximately 70 - 90% of phosphatic fertilizers applied to crops are fixed in soil as Ca, Fe, and Al metal cations, which are insoluble and thus not readily available for plant uptake. Therefore, most soils are deficient in plant available P. This is usually rectified by applying phosphate fertilizers continuously, although this is not economically viable or environmentally acceptable. The present paper reviews the mechanisms involved with phosphate solubilization and mineralization by phosphate solubilizing microorganisms (PSMs) with the associated factors that determine the success. PSMs are effectively involved in mediating the bioavailability of soil P. Their contribution includes mineralization of organic P solubilization of inorganic P minerals, and storing sizable amounts of P in biomass through different mechanisms such as the production of organic and inorganic acids, H₂S, siderophores, exopolysaccharides, and production of enzymes such as phosphatases, phytase, and phosphonatases/C-P lyases, which are capable of chelating the metal ions, forming complexes, and making plant available P. PSMs manifest a wide range of metabolic functions in different environments, resulting in significantly higher plant growth, enhanced soil properties, and increased biological activities. Therefore, development of bio-inoculants with efficient novel PSM strains and further investigations on exploring such strains from diverse ecological niches with multifunctional plant-growth-promoting traits are needed.

• Applied Biological Chemistry
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• v.44 no.4
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• pp.251-256
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• 2001

To develop biofertilizer solubilizing inorganic phosphate, a bacterium having high abilities to solubilize inorganic phosphate were isolated from cultivated soils. The strain was identified to Aeromonas hydrophila DA57, based on the physiological and biochemical properties. The optimum temperature and initial pH to solubilize insoluvle phosphate in sucrose minimal medium were $30^{\circ}C$ and pH 7.0, respectively. In these conditions phosphate solubilizing activities of the strain against three types of insoluble phosphate were quantitatively determined. It was possivle to distinguish between solubilization through release of gluconic acid and still unknown mechanism. Aemmonas hydrophila DA57 harbored a 4.5 kb cryptic plasmid.

• Korean Journal of Organic Agriculture
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• v.23 no.2
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• pp.291-299
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• 2015

This study aimed to investigate the effect of inoculation time of phosphate- solubilizing Kluyvera sp. CL2 on fruit quality in cultivation of Campbell early' grape. When phosphate-solubilizing strain was treated at the stone-hardening stage, soil phosphorous increased, exchangeable cations such as K, Ca and Mg also increased. Soil pH was not changed severely due to the soil buffer capacity. Water soluble phosphate concentrations did not decrease heavily up to 20 days after inoculation. When this strain was treated at the berry-softening stage, soil phosphate solubilization ratio was high, cluster weight and sugar content also increased. Both anthocyanin contents and Hunter's values were seen to be significant when inoculation times were stone-hardening stage and berry-softening stage, in particular, increase of Hunter's value a resulted in the improvement of coloration. From these results, we could find that the inoculation of phosphate-solubilizing Kluyvera sp. CL2 at berry-softening stage was the most effective in improvement of fruit productivity and quality in cultivation of'Campbell early' grape.

• Applied Biological Chemistry
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• v.40 no.4
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• pp.329-333
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• 1997

Phosphate solubilizing microorganisms (1,000 bacteria and 200 fungi) 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 Penicillium sp. GL-101, based on the morphological characteristics of conidiophore and conidia; flask shape of phialide, simple branching type of conidiophore, and columnar shape of conidial head, 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 $25^{\circ}C$ and pH 7.5, respectively. In these optimum conditions, phosphate solubilizing activities of Penicillium sp. GL-101 against four types of insoluble phosphate: tricalcium-phosphate, aluminium phosphate, hydroxyapatite and rock phosphate, were quantitatively determined. As results, this fungus highly discharged free phosphates to the culture broth with the concentrations of 1,152 ppm against tricalcium-phosphate, 565 ppm against rock phosphate, 292 ppm against aluminium phosphate, and 217 ppm against hydroxyapatite, respectively.

• Korean Journal of Microbiology
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• v.49 no.4
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• pp.398-402
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• 2013

This study was to investigate beneficial effects of microbial mixture on red pepper which was capable of promoting plant growth by solubilizing insoluble phosphate as well as protecting plants from pathogenic attack. Saccharomyces sp. L13 was isolated for phosphate solubilizing activity on aluminium phosphate, tricalcium phosphate, calcium hydrophosphate, and magnesium hydrophosphate. On the other hand, Bacillus sp. L32 was isolated for antagonistic activity against Phytophthora capsisi and Colletotrichum gloeosporioides, causing Phytophthora blight and Anthracnose disease in pepper, respectively. The strain L32 exhibited antagonistic activities both under dual culture assays and detached leaves assays. The each strain under the condition of mixed cultivation exhibited the same growth rates as one under pure cultivation. In greenhouse study, the mixed culture showed the both effect of plant growth promotion and reduction of disease symptom development against P. capsisi and C. gloeosporioides providing a potential as effective microbial agent for plant husbandry.