Development of a high-throughput method for screening readily biodegradable chemicals

Current standard test methods for assessing biodegradation of chemicals are laborious and not suited for high-throughput screening of chemicals because of both the required volume of the test medium and the limited possibility for automation of measurements of biodegradation. A high-throughput method (HTM) should be miniaturized, suitable for automation, and based on generic parameters that can indicate biodegradation of any chemical. The aim of this study was to develop an HTM based on bacterial proliferation (i.e., growth) as an indicator of biodegradation, measured by flow cytometry. Natural bacterial communities were exposed to reference chemicals in 96-well plates for up to 14 days at 19 °C and the results compared with parallel standard biodegradation screening tests for freshwater (Organisation for Economic Co-operation and Development [OECD] 301F) and seawater (OECD 306). Increased bacterial growth, compared with nonexposed inocula, was used as an indication of biodegradation. Sodium benzoate induced a significant growth response that corresponded to the biodegradation experiments in both freshwater and marine water. Aniline induced a lower frequency of significant growth compared with the frequency of positive biodegradation results, whereas caffeine induced a higher frequency and more rapid growth response compared with biodegradation results. This shows the potential for an HTM for biodegradation testing using bacterial growth.