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Isolation and phosphate‐solubilizing ability of a fungus, Penicillium sp. from soil of an alum mine

The use of microorganisms to solubilize elemental phosphorus from insoluble rock phosphate is a promising method to greatly reduce not only environmental pollution but also production costs. Phosphate‐solubilizing microorganisms were isolated from soils in China, and a fungus strain (PSM11‐5) from a soil sample from an alum mine, with the highest phosphate solubilization potential, was selected and identified as a Penicillium sp. Strain PSM11‐5 could grow in buffered medium with pH values between 3.0 and 8.0 and showed phosphate solubilizing activity at pH values from 5.0 to 8.0. It also exhibited a degree of tolerance to the heavy metal ions, Cd2+, Co2+, and Cr6+. PSM11‐5 could rapidly solubilize tricalcium phosphate, and a high phosphate‐solubilizing efficiency of 98% was achieved in an optimized medium. The strain could solubilize rock phosphate and aluminum phosphate with a solubilizing efficiency of approximately 74.5%, but did not solubilize iron phosphate. Solubilization of phosphate depended on acidification. Analysis of PSM11‐5 culture supernatants by capillary electrophoresis showed that tricalcium phosphate was solubilized to PO43– and Ca2+, and that the organic acid produced by the fungus was mainly gluconic acid at approximately ca. 13 g l–1. In addition, PSM11‐5 produced ca. 830 mg l–1 of citric acid when it was used to solubilize rock phosphate. These excellent properties of strain PSM11‐5 suggest that the fungus has potential for agricultural and industrial utilization. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)