土壤中微生物植酸酶的活性及其提高方法与应用

Microbial phytase activity in soils and methods to improve the activity and application:a review

磷是有限不可再生资源,土壤缺磷是植物生长和农作物生产的主要限制因子之一。无机磷肥施入土壤后,极易被土壤固相吸附或与金属阳离子形成难溶性络合物或转化为有机磷,导致其生物可利用性降低。土壤磷主要以有机磷形式存在,占比20%-80%。有机磷又以植酸(盐)为主要成分,占比约50%。植酸不可被植物直接吸收利用,需在专一性酶植酸酶作用下经脱磷酸化水解释放磷供植物吸收。土壤植酸酶主要来源于微生物,易受温度、pH、土壤吸附、钙含量及钙磷比、底物含量和有效性等影响,导致酶活降低甚至失活。如何保持或提高土壤中植酸酶活性,进而提高土壤内源植酸磷的利用率,对降低外源磷肥施加和保障农业生产具有重要意义。本文综述微生物植酸酶的来源、分类与作用机制及土壤中植酸酶活性的影响因素,重点阐述保持或提高其活性的方法及实际应用效率。针对土壤植酸酶活性低和稳定性差的问题,对通过调控最适pH范围、提高热稳定性、将植酸酶负载于纳米材料和基因工程改造等改善植酸酶性质的方法进行展望。综述内容可为理解土壤中植酸酶活性的影响因素,进而提高土壤内源植酸磷的利用效率提供理论依据和技术参考,对减少外源磷肥施用、降低磷流失和土壤面源/水体污染风险及保障农业可持续发展具有一定的现实意义。

Phosphorus(P)is a finite and non-renewable resource.Soil P deficiency is a main limiting factor for crop growth and agricultural production.Once entering into soils,inorganic P(Pi)in fertilizers is readily being fixed by soil solid phase,binds to metal ions to form the insoluble complex,or transform into organic P(Po)which fails to be directly uptake by plants.Soil P mainly exists as Po,which accounts for 20%-80% of total P.Phytic acid or phytate is the predominant form of Po,accounting for about 50% of Po.Phytate can not be directly uptake by plants,while can release P via dephosphorylation by the specific enzyme phytase.Phytase is mainly secreted by microbes and its activity is affected by temperature,pH,soil adsorption,Ca content,Ca/P ratio and substrate concentration and availability,leading to reduced activity or inactivation.Therefore,it is of great importance for reducing the application of exogenous P fertilizer and ensuring agricultural production to understand how to maintain or improve phytase activity in soils and improve the utilization of soil endogenous phytate.Thus,this paper reviews the sources,classification,and function mechanisms of microbial phytase and influencing factors of soil phytase activity,focusing on methods to maintain or improve phytase activity and the application efficiencies.In terms of the low activity and poor stability,methods to improve phytase properties including adjusting optimal pH range,improving thermal stability,loading phytase on nano-materials,and genetic engineering,are proposed.As such,this review is expected to help better understand the influencing factors of phytase activity in soil and provide theoretical and technical supports to improve endogenous phytic acid utilization efficiency.This is of great importance to reduce the application rate of P fertilizer,P loss,and risk of soil non-point source/water pollution and ensuring agricultural sustainable development.