Structural characterization of natural nanomaterials: potential use to increase the phosphorus mineralization.

Nanomaterials like nanoclays occur widely in nature. The use of nanomaterials as immobilization support improves enzymatic stability and catalytic activity against other materials. The aims of this study were: i) to characterize natural allophanic clay and nanoclay fraction with and without organic matter from an Andisol and ii) to evaluate allophanic and montmorillonite nanoclays as support to immobilize acid phosphatase. The used Andisol belongs to Piedras Negras Series from Southern Chile. Clays and nanoclays extracted were characterized by TEM, SEM, EDX, ED and AFM. The enzymatic activities were measured with 8 nitrophenylphosphate (8NPP) as substrate. The kinetics parameters (V max and K m) were calculated according to Michaelis–Menten equation. The microscopy analysis showed that the methodology of the nanoclays extraction allowed obtaining aggregates with high proportions of mesoporous, which are suitable to enzymatic immobilization. The nanoclay fractions showed that organic matter governs the feature behavior and is very recalcitrant, suggesting that this nano8fraction plays an important role in carbon sequestration. Finally, we demonstrated that the immobilized phosphatase has a significant increase both in catalytic efficiency (V max /K m) and in substrate affinity (1/K m) when allophanic and montmorillonite nanoclays were used as material support.