Protected activity of a phytase immobilized in mesoporous silica with benefits to plant phosphorus nutrition

Phosphorus (P) is one of the main nutrients required for plant growth and is absorbed and metabolized in the form of orthophosphate ions (Pi). In agriculture, P is a major component of fertilizers. Forecast shortages in P mine stocks within the coming decades call for alternative sources of this element for agricultural use. In the present study, we explore the possibility of incorporating phytase near the plant root system. Phytase is an enzyme capable of mobilizing the main organic form of P as phytate, which can represent up to 90 % of the total P stock in soils. We report the immobilization of phytase in KIT-6 silica mesoporous materials with large pores of 8.6 nm. The enzymatic activity is localized in the porous network, and the main kinetic features of the free phytase appear to be maintained within the functional material (pHopt = 5–5.5 and T opt = 55 °C). Most importantly, the enzyme immobilized in the pores shows a higher temperature stability and appears to be protected from protease degradation. Finally, phytase-loaded KIT-6 proved efficient at hydrolyzing phytate and delivering inorganic P to growing Medicago truncatula plants, which accumulated this newly available P in both roots and shoots.