Abstract:

Phytate is the pdominant form of soil phosphorus (P), which cannot be directly taken up by plants, but can be hydrolyzed by the specific enzyme phytase via dephosphorylation. However, phytase activity is affected by environmental factors, resulting in reduced activity or deactivation. Consequently, there is growing interest in finding ways to maintain or improve phytase activity in soils to improve the utilization of soil endogenous phytate-P has attracted increasing attentions. Nanomaterial-immobilization can improve the stability and activity of phytase in the environment. This paper provides a review on the preparation technology, product characteristics, advantages and disadvantages of chitosan, hydroxyapatite, graphene oxide and mesoporous silicon dioxide nanocarriers, and analyzes the preparation methods (adsorption, covalent binding, embedding, cross-linking, loading, etc.), characterization methods, loading efficiency, loaded-enzyme activity, and reaction mechanisms of different nanocarriers immobilized phytase. It was found that 1) nanomaterial-immobilized phytase is more stable than free phytase under high temperature, acid, alkali and in the presence of metal ions, which is an effective way to improve the utilization of soil endogenous phytase-P; 2) the activity of nanomaterial-immobilized phytase depends on carrier species, phytase source and characteristics, and preparation methods. Phytase source and characteristics should be considered when selecting suitable carrier and immobilization methods. Given that the practical application of nanomaterial-immobilized phytase is limited, attention can be paid to 1) microbes that produce phytase with high stability and activity; 2) carriers with high stability and loading rate, which can be used to develop nanomaterials; 3) immobilization methods with high loading rate and low cost to maintain enzyme activity during production, transportation, and storage; and 4) the applicability of different immobilized phytases in different soils. The information enhances our understanding of the characteristics of nanomaterial-immobilization technology and limiting factors during practical applications. It also provides technical support for the development of high loading ratio and stability to improve the utilization of soil endogenous phytate-P, which is important for reducing exogenous P fertilizer application, minimizing the risk of P loss, and ensuring sustainable agricultural production.

Key words: nanomaterial, phytase, immobilization, influencing factor, application efficiency

摘要：

植酸是土壤磷的重要组分部分，但难以被植物吸收利用，需在专一性酶——植酸酶作用下，经脱磷酸化过程矿化水解释放磷酸（盐）。然而，植酸酶活性极易受环境因素影响，导致酶活性降低甚至失活。如何保持或提高土壤中植酸酶的活性，进而提高土壤内源植酸磷的利用率已引起广泛关注。植酸酶经纳米材料固定化可提高其环境稳定性和活性。总结了不同纳米载体的制备技术、产品特征及优缺点，深入分析了不同纳米载体固定化植酸酶的制备及表征方法、负载酶的酶活性及作用机理。分析发现：1）功能载体固定化植酸酶的环境稳定性（高温、强酸、强碱和金属离子等）和催化水解效率显著优于游离植酸酶，是提高土壤内源植酸磷利用效率的有效途径；2）纳米材料固定化植酸酶的稳定性受载体种类、植酸酶来源与特性及制备方法的影响，应根据植酸酶来源与特性选择适宜的载体种类和固定化方法。针对固定化植酸酶实际应用中的局限性，今后应关注如下几方面：1）稳定性好、活性高的植酸酶生产菌；2）稳定性好、高负载率载体，制备纳米级材料；3）负载率高、成本低的固定化方法，在生产、运输、使用和储存过程中保持酶活；4）不同种类固定化植酸酶在不同种类土壤中的适用性。该综述可为理解纳米材料固定化植酸酶制备技术特征和实际应用影响因素提供理论依据，为开发高负载率、高稳定性固定化植酸酶制剂，进而提高土壤内源植酸磷的生物利用率提供科学依据，对降低外源磷肥施用、降低磷流失污染风险和保障农业生产具有一定的现实意义。

关键词: 纳米材料, 植酸酶, 固定化, 影响因素, 应用效率