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World J Microbiol Biotechnol (2008) 24:10591065 DOI 10.1007/s11274-007-9575-4
ORIGINAL PAPER
Exopolysaccharide: a novel important factor in the microbial dissolution of tricalcium phosphate
Yanmei Yi Weiyi Huang Ying Ge
Received: 16 May 2007 / Accepted: 26 September 2007 / Published online: 18 October 2007 Springer Science+Business Media B.V. 2007
Abstract Four strains (Enterobacter sp. EnHy-401, Arthrobacter sp.ArHy-505, Azotobacter sp.AzHy-510 and Enterobacter sp.EnHy-402) which have the ability to solubilize tricalcium phosphate (TCP) were used to study the mechanism of P-solubilization. It was found that three phosphate solubilizing bacteria (EnHy-401, ArHy-505 and AzHy-510) producing exopolysaccharide (EPS) have a stronger ability for P-solubilization than isolate EnHy-402 without EPS production, of those, the strain EnHy-401 with the highest EPS production and efcient organic acids on P-solubilization had a stronger capacity for P-solubilization than the others. Further studies demonstrated that addition of EPS into medium could increase the amount of phosphorus solubilized by organic acid, but failed to release phosphorus from TCP alone. The synergistic effects of EPS and organic acid on TCP solubilization varied with the origin and the concentration of EPS in medium. EPS produced by EnHy-401 was most effective in promoting phosphorus release at an optimal concentration in medium. The increase of P-solubilization brought by EPS attributed to the participation of EPS led to the change in homeostasis of P-solubilization, pushing it towards P dissolved by holding free phosphorus in the
medium, consequently resulting in greater phosphorus released from insoluble phosphate. We therefore suggest that EPS with ability of phosphorus-holding may be a novel important factor in the microbial dissolution of TCP except for organic acid.
Keywords Exopolysaccharide Organic acid
Tricalcium phosphate Phosphorus holding
Phosphate solubilizing bacteria
AbbreviationsP PhosphateTCP Tricalcium phosphateEPS ExopolysaccharidePSB Phosphate solubilizing bacteriaPSM Phosphate solubilizing microorganism NBRIP National Botanical Research Institutes phosphate growth medium
Introduction
Phosphorus is an essential element for plant growth and can only be assimilated as soluble phosphate species (Illmer and Schinner 1992). However, the concentration of soluble P in soil is usually very low, normally at levels of 1 mg kg1 or less (10 M HB2PO4) (Goldstein 1994). In agriculture, deciency of soil P is one of the most important chemical factors restricting plant growth. As low P status tends to limit the yield of arable crops, a large amount of soluble...