Author
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ELZOBAIR, KHALID - Colorado State University |
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STROMBERGER, MARY - Colorado State University |
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Ippolito, James |
Submitted to: Chemosphere
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 3/10/2015 Publication Date: 4/1/2015 Publication URL: http://handle.nal.usda.gov/10113/61134 Citation: Elzobair, K.A., Stromberger, M.E., Ippolito, J.A. 2015. Stabilizing effect of biochar on soil extracellular enzymes after a denaturing stress. Chemosphere. Available: http://dx.doi.org/10.1016/j.chemosphere.2015.03.018. Interpretive Summary: A laboratory incubation study examined the effects of a hardwood, fast-pyrolysis biochar amendment on potential activities of six extracellular enzymes in soil. Soil was exposed to microwave energy at increasing levels of power (or stress) to determine if biochar would limit the loss of enzyme activity when exposed to a denaturing stress. It was found that the effect of biochar on enzyme activity was dependent on the amendment rate and the enzyme itself, and thus concluded that the ability of biochar to stabilize certain enzymes from denaturing stress is partly dependent on the molecular size and isoelectric point of the enzyme. Technical Abstract: Stabilization of extracellular enzymes may maintain enzymatic activity for ecosystem services such as carbon sequestration, nutrient cycling, and bioremediation, while protecting enzymes from proteolysis and denaturation. A laboratory incubation study was conducted to determine whether a fast pyrolysis biochar (CQuest) derived from oak and hickory hardwood would stabilize extracellular enzymes in soil and prohibit the loss of potential enzyme activity following a denaturing stress, in this case microwaving. Soil was incubated in the presence of biochar (0, 1, 2, 5, or 10% by weight) for 36 days and subsequently exposed to microwave energies of 0, 400, 800, 1600, or 3200 Joules per gram of soil. Soil enzymes (ß-glucosidase, ß-D-cellobiosidase, N-acetyl-ß-glucosaminidase, phosphatase, leucine aminopeptidase, and ß-xylosidase) were analyzed by fluorescence-based assays. Biochar amendment significantly reduced the potential activity of leucine aminopeptidase and ß-xylosidase after the incubation period and prior to stress exposure. Microwaving provided stress through heat and loss of soil water, although at the lowest stress level (400 Joules per gram of soil) soil water loss was significantly reduced in soil amended with 10% biochar. Enzyme stabilization was demonstrated for ß-xylosidase, whereby intermediate biochar application rates (1 and 5 %) prevented a complete loss of this enzyme’s potential activity after soil was exposed to 400 (1% biochar treatment) or 1600 (5% biochar treatment) Joules of microwave energy per gram of soil. Potential activities of ß-glucosidase, ß-D-cellobiosidase, N-acetyl-ß-glucosaminidase, and phosphatase enzymes were not affected by biochar, and activities of these enzymes decreased significantly with increasing levels of microwave energy. We concluded that biochar has the potential to prevent evaporative losses of soil water to some degree and stabilize certain extracellular enzymes such as ß-xylosidase so that activity is maintained after a denaturing stress. This effect was dependent, however on biochar application rate and the enzyme itself. Furthermore, while biochar may reduce the potential activity of certain extracellular enzymes in soil, this phenomenon was not universal as the majority of enzymes assayed in this study were unaffected by exposure to biochar. |