Extracellular enzymes play a key role in mediating organic matter decomposition in soils and the mobility of enzymes is largely controlled by their interaction with soil surfaces. The introduction of pyrogenic products, including biochar produced for the purpose of carbon sequestration or soil health management, may alter the ecological functioning of soil. In this work, we studied the adsorption of four representative soil extracellular enzymes (urease, invertase, α-amylase and protease) to biochar (derived from wood biomass and wheat straw produced at different pyrolysis temperatures, and a wildfire pine char) and soil mixed with biochar. A pH-edge adsorption experiment showed that, for all biochar/enzyme combinations, adsorption of all extracellular enzymes decreased as pH increased from 4 to 9. This pH dependency suggests that electrostatic interaction was the primary adsorption mechanism. Equilibrium enzyme adsorption data was best fit by the Langmuir isotherm and adsorption capacity varied significantly with enzyme type, ranging from 67 to 232 mg·g−1 for urease and 0 to 11 mg·g−1 for the others at pH 5.0. Enzyme adsorption also differed among biochars with or without surface oxidation treatment. Correlations between enzyme adsorption data and biochar properties demonstrated the relevance of enzyme sizes, biochar surface porous structure, and surface chemical functionality in determining biochar adsorption capacity and affinity for enzymes. Soil adsorption experiment showed that biochar addition can enhance or reduce soil adsorption of enzymes, depending on the relative enzyme affinity between the soil and biochar. These findings indicate that pyrogenic organic matter has varying impacts on the mobility of soil extracellular enzymes through direct adsorption and potentially affect the activity and stability of enzymes, and ultimately soil carbon and nutrient cycling.

中文翻译：

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生物炭对细胞外酶的吸附：酶和生物炭特性的影响


细胞外酶在介导土壤中有机物分解中起关键作用，酶的迁移性在很大程度上受其与土壤表面的相互作用的控制。引入热原产品，包括为碳封存或土壤健康管理而生产的生物炭，可能会改变土壤的生态功能。在这项工作中，我们研究了四种代表性土壤细胞外酶 （脲酶、转化酶、α-淀粉酶和蛋白酶） 对生物炭 （来源于在不同热解温度下生产的木材生物质和小麦秸秆，以及野火松炭） 和土壤与生物炭混合的吸附。pH 边缘吸附实验表明，对于所有生物炭/酶组合，随着 pH 值从 4 增加到 9，所有细胞外酶的吸附都会降低。这种 pH 依赖性表明静电相互作用是主要的吸附机制。Langmuir 等温线最拟合平衡酶吸附数据，吸附容量随酶类型变化显著，在 pH 值为 5.0 时，脲酶的吸附容量范围为 67 至 232 mg·g-1，其他酶的吸附容量范围为 0 至 11 mg·g-1。酶吸附在有或没有表面氧化处理的生物炭之间也不同。酶吸附数据与生物炭特性之间的相关性表明，酶大小、生物炭表面多孔结构和表面化学功能在确定生物炭吸附能力和对酶的亲和力方面的相关性。土壤吸附实验表明，生物炭添加可以增强或减少土壤对酶的吸附，这取决于土壤与生物炭之间的相对酶亲和力。 这些发现表明，热原有机质通过直接吸附对土壤细胞外酶的迁移具有不同的影响，并可能影响酶的活性和稳定性，并最终影响土壤碳和养分循环。