el-Din Sharabi N, Bartha R
Department of Biochemistry and Microbiology, Cook College, Rutgers University, New Brunswick, New Jersey 08903-0231.
Appl Environ Microbiol. 1993 Apr;59(4):1201-5. doi: 10.1128/aem.59.4.1201-1205.1993.
Conversion to CO2 upon incubation in aerobic soil is one of the standard test procedures to assess biodegradability. It may be measured with unlabeled test compounds in biometer flasks. In this case, the background CO2 evolution by unamended soil is subtracted from the CO2 evolution by the amended soil and the resulting net CO2 evolution becomes the measure of biodegradation. Alternately, 14CO2 release from radiocarbon substrates is measured to assess biodegradability. Both approaches measure ultimate (complete) biodegradation and bypass the theoretical and technical limitations of residue analysis. This report examines the underlying assumptions that, except for carbon content, conversion percentage to CO2 is relatively independent of chemical composition, that CO2 production is proportional to the amount of added test compound, and that the background CO2 evolution of the soil is not influenced by the test substance. Work with unlabeled and radiolabeled substrates proved the first two assumptions to be essentially correct. However, more than half of net CO2 production may represent the mineralization of biomass and soil organic matter, some of it unrelated to the test compound. The soil microbial community in its nongrowing steady state appears to convert a much lower percentage of a radiocarbon substrate to 14CO2 than a growing soil community that responds to a substantial substrate addition. These findings may help to improve test methods and may aid in the interpretation of test results.
在有氧土壤中培养时转化为二氧化碳是评估生物降解性的标准测试程序之一。可以在生物测定瓶中用未标记的测试化合物进行测量。在这种情况下，从添加了测试化合物的土壤中释放的二氧化碳中减去未添加测试化合物的土壤释放的背景二氧化碳，所得的净二氧化碳释放量就成为生物降解的度量。另外，测量放射性碳底物释放的(^{14}CO_2)以评估生物降解性。这两种方法都测量最终（完全）生物降解，并绕过了残留分析的理论和技术限制。本报告研究了以下基本假设：除碳含量外，转化为二氧化碳的百分比相对独立于化学成分；二氧化碳的产生与添加的测试化合物的量成正比；土壤的背景二氧化碳释放不受测试物质的影响。对未标记和放射性标记底物的研究证明前两个假设基本正确。然而，净二氧化碳产生的一半以上可能代表生物量和土壤有机质的矿化，其中一些与测试化合物无关。处于非生长稳态的土壤微生物群落似乎比响应大量底物添加的生长土壤群落将放射性碳底物转化为(^{14}CO_2)的百分比要低得多。这些发现可能有助于改进测试方法，并有助于解释测试结果。
