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Enhanced solubilization of rock phosphate by Penicillium bilaiae in pH-buffered solution culture

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Little is known about how pH-buffering capacity affects phosphorus (P) solubilization by Penicillium bilaiae. This study compared solubilization of rock phosphate (RP) by P. bilaiae in nonbuffered (pH 5.0) and buffered (pH 7.0) media. Fungal growth reached the stationary phase around day 12 and was slightly enhanced in the buffered medium. The fungus reduced solution pH from 5.0 to 4.1 in the nonbuffered medium and from 7.0 to 4.9 in the buffered medium by day 12. Phosphorus concentrations increased after day 9 more in the buffered than in the nonbuffered media (53 and 5 mg P·L–1, respectively, on day 12). On day 12, higher concentrations of citric and oxalic acids were detected in the buffered (2.0 and 1.2 g·L–1, respectively) than nonbuffered media (0.5 and 0.04 g·L–1, respectively). Solubilization of RP was simulated without P. bilaiae in solutions equivalent to the nonbuffered and buffered cultures of P. bilaiae grown with RP. After a 24 h incubation, the P concentrations were of similar magnitudes to those observed in the P. bilaiae culture (18 and 47 mg P·L–1, respectively, in the nonbuffered and buffered media). Under increased pH-buffering conditions, the enhanced production of citric and oxalic acids led to significant RP solubilization.Key words: phosphorus solubilization, pH buffering, Penicillium bilaiae, citric acid, oxalic acid.

On sait peu de choses de la façon dont le tamponnage du pH affecte la solubilisation de phosphore (P) chez Penicillium bilaiae. Cette étude a comparé la solubilisation du phosphate naturel de P. bilaiae en milieu non tamponné (pH 5,0) et tamponné (pH 7,0). La croissance fongique a atteint la phase stationnaire autour du 12ième jour et était légèrement augmentée en milieu tamponné. Le champignon a réduit le pH de la solution de 5,0 à 4,1 en milieu non tamponné et de 7,0 à 4,9 en milieu tamponné au jour 12. La concentration de phosphore a davantage augmenté après le jour 9 en milieu tamponné que non tamponné (soit 53 et 5 mg P·L–1 respectivement, au jour 12). Au jour 12, des concentrations plus élevées d'acide citrique et d'acide oxalique ont été détectées dans le milieu tamponné (respectivement 2,0 et 1,2 g·L–1) que dans le milieu non tamponné (respectivement 0,5 et 0,04 g·L–1). La solubilisation de phosphate naturel était stimulée en absence P. bilaiae dans des solutions équivalant à des cultures non tamponnées et tamponnées de P. bilaiae cultivées en présence de phosphate naturel. Après une incubation de 24 h, les concentrations de P étaient à des niveaux similaires aux niveaux retrouvés dans une culture de P. bilaiae (18 et 47 mg P·L–1, en milieux non tamponnés et tamponnés respectivement). Sous de meilleures conditions de tamponnage du pH, la production plus élevée d'acide citrique et d'acide oxalique résulte en une solubilisation significative du phosphate naturel.Mots clés : solubilisation du phosphore, tamponnage du pH, Penicillium bilaiae, acide citrique, acide oxalique.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: November 1, 2006

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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