Role of metal complexation on the solubility and enzymatic hydrolysis of phytate

Abstract

Phytate is a dominant form of organic phosphorus (P) in the environment. Complexation and precipitation with polyvalent metal ions can stabilize phytate, thereby significantly hinder the hydrolysis by enzymes. Here, we studied the stability and hydrolyzability of environmentally relevant metal phytate complexes (Na, Ca, Mg, Cu, Zn, Al, Fe, Al/Fe, Mn, and Cd) under different pHs, presence of metal chelators, and thermal conditions. Our results show that the order of solubility of metal phytate complexes is as follows: i) for metal species: Na, Ca, Mg > Cu, Zn, Mn, Cd > Al, Fe, ii) under different pHs: pH 5.0 > pH 7.5), and iii) in the presence of chelators: EDTA> citric acid. Phytate-metal complexes are mostly resistant towards acid hydrolysis (except Al-phytate), and dry complexes are generally stable at high pressure and temperature under autoclave conditions (except Ca phytate). Inhibition of metal complex towards enzymatic hydrolysis by Aspergillus niger phytase was variable but found to be highest in Fe phytate complex. Strong chelating agents such as EDTA are insufficient for releasing metals from the complexes unless the reduction of metals (such as Fe) occurs first. The insights gained from this research are expected to contribute to the current understanding of the fate of phytate in the presence of various metals that are commonly present in agricultural soils.

Soy and mustard effectively mobilize phosphorus from inorganic and organic sources

“…These organic substances (including LMWOA) might act as substrate for microorganisms, which produce additional phytases that effectively hydrolyze phytate in the rhizosphere of soy, as demonstrated earlier (Lambers et al 2008;Wang and Lambers 2020;Wu et al 2018). This is supported by previous studies showing that the addition of commercial fungal phytases (Hayes et al 2000;Sun et al 2021) as well as the inoculation with phytate-mineralizing bacteria (Ramesh et al 2011;Richardson et al 2000) increased P availability from phytate for soy, wheat, and several pasture species. Similarly, mycorrhizal symbionts have been found to effectively mobilize P from phytate (Wang et al 2017;Zhang et al 2016).…”

The effect of popping, soaking, boiling and roasting processes on antinutritional factors in chickpeas and red kidney beans

“…Sun et al . (2021) suggested that although there are negligible differences in the thermal stability of metal phytates, Ca phytate is said to decompose significantly more (28%) than Al, Fe, Cu, Zn, Mn, Cd, Na and Mg phytates (0.05%–1.6%) under the same thermal treatments. Clearly, further analysis is required to determine the types of phytate‐mineral complexes and their thermal stability in our tissue samples.…”

Insight into phytase-producing microorganisms for phytate solubilization and soil sustainability

“…At all pH ranges, phytate combines with calcium to form soluble complexes (Ca 1 - or Ca 2− phytate) or insoluble precipitates such as Ca 3− phytate. Strong chelating chemicals like EDTA are insufficient to dissolve complexes of metals without first reducing the metals (like Fe) ( Sun et al, 2021 ). Phytate may undergo severe immobilization, which prevents it from being hydrolyzed by phytase, resulting in its limited availability and significant accumulation in soils.…”

“…Aspergillus niger phytase varied in its ability to prevent metal complexes from being hydrolyzed by enzymes; however, it has been discovered that the Fe phytate complex showed the most outstanding inhibition. Strong chelating chemicals like EDTA are insufficient to dissolve complexes of metals without first reducing the metals (like Fe) ( Sun et al, 2021 ). Moreover, the interactions among phytate-mineralizing bacteria, bacteria-eating nematodes, and mycorrhizal fungi also boost plant P uptake from phytate in soils with significant P adsorption ( Ranoarisoa et al, 2020 ).…”

“…As the metallic cations of Ca, Fe, K, Mg, Mn, and Zn are tightly bound by the negatively charged phosphate in PA, they become insoluble and are hence not available for plants ( Azeem et al, 2014 ; Sun et al, 2021 ). Small quantities of inorganic phosphorus added to the rhizosphere might act as a stimulator to phytic acid mineralization, thus improving plant phosphorus feeding ( Elhaissoufi et al, 2022 ).…”