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Polyvalent Cation Effects on myo ‐Inositol Hexa kis Dihydrogenphosphate Enzymatic Dephosphorylation in Dairy Wastewater
Author(s) -
Dao Thanh H.
Publication year - 2003
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2003.6940
Subject(s) - phytase , chemistry , dephosphorylation , phosphorus , manure , bioavailability , enzyme , phosphatase , food science , citric acid , chromatography , biochemistry , nuclear chemistry , agronomy , organic chemistry , bioinformatics , biology
Information is needed on organic polyphosphates such as myo ‐inositol 1,2,3,5/4,6‐hexa kis dihydrogenphosphate or phytate (IP6) contribution to the sources and sinks of dissolved phosphorus (PO 4 –P) in the soil–manure–water system. Effects of Na + , Ca 2+ , Al 3+ , and Fe 3+ and cation to IP6‐P mole ratios on the enzymatic dephosphorylation of IP6 were studied to determine controlling mechanisms of dephosphorylation and persistence in manure. Phytate‐ and PO 4 –P were analyzed by high‐performance liquid chromatography. Phytate dephosphorylation by Aspergillus ficuum (Reichardt) Henn. phytase EC 3.1.3.8 decreases by 50 ± 3.6 and 40 ± 4% at pH 4.5 and 6, respectively, as Ca 2+ concentrations increase and cation to IP6‐P mole ratios reach 6:6. Polyanionic IP6 has a high affinity for Al 3+ and Fe 3+ and reductions in dephosphorylation average 27 and 32% at a cation to IP6‐P mole ratio of 1:6 for Al 3+ and Fe 3+ , respectively, while reaching more than 99% at a mole ratio of 6:6. A phytase‐hydrolyzable phosphorus (PHP) fraction is native to ruminant animal manure and is proportional to total solids (TS) concentration in 1 to 100 g L −1 suspensions. Added phytase, in effect, increases water‐extractable P content of manure and the risk of environmental P dispersion. As the bioavailability and ecological effect of IP6‐P appear to be regulated not only by pH‐controlled enzyme activity but also by the associated counterions, the differential protective effects of cations influence the accuracy of manure PHP fraction estimates and increase phytate resistance to enzymatic dephosphorylation that may lead to its persistence in manure.