Research advances on the measurement methods for soil hydrolytic enzymes activities

Soil hydrolytic enzymes play an important role for maintaining carbon and nutrient cycle of ecology system as they are directly involved in the soil organic matter mineralization. The methodological differences among researchers and laboratories influenced the determining on proper measurement methods. The review summarized the research results on measuring method of soil enzymes activities involved soil storage methods, selection of substrate and incubation conditions in recent circa 20 years. To extract and purify the enzyme from soil have been left unsuccessful for the complexity of broad origin and existing states, so soil enzyme activity assays were commonly based on the quantitative evaluation of the product released or of the substrate consumed. Colorimetric methods based on artificial p-nitrophenol substrate had been used widely for the low cost. Based on the absence of the uniform international standard, and hard contrast among investigator results, the corresponding measures should be token to run measurement of soil hydrolytic enzymes activities recently. We recommended some manipulation: 1) conduct assay with fresh soil whenever possible, or soil stored shortly at 4 ℃ or -20 ℃; 2) opt substrate based on international standards and use saturated substrate concentrations to ensure Vmax being measured; 3) run the assay at a pH of buffer similar to that of soil; 4) omit inhibitors of microbial proliferation within 4 h incubation. Some research orientation currently were also suggested: 1) to enrich the research categories of soil hydrolytic enzymes; 2) develop the measurement methods of fluorimetric determination with high sensitivity, small quantity of soil sample and short incubation time; 3) establish primary standard methods by studying the catalytic kinetic of hydrolytic enzymes in typical soil types.