PARENT SESSION
PW7 - Biotransformation / Metabolisms / Degradation
Wednesday, 20 November 2002
8:00 AM to 6:30 PM
Exhibit Hall
(P784) The impact of acclimation or ageing periods on the composition of the microbial composition of marine inocula.
Snape, Jason*,1, Bernhard, Fuchs2, 1 AstraZeneca Global SHE, Brixham, Devon, UK2 Max Planck Institute, Bremen, Germany
ABSTRACT- Acclimation periods are used within biodegradability testing to serve two distinct purposes: the reduction of exogenous carbon in the test and control flasks thus improving analytical precision, and the reduction in intra-test variability between replicate flasks. To achieve these goals two approaches exist. The first is basically an ageing process where the inoculum is suspended in the test media for a period of up to seven days under the standardised incubation conditions (temperature and agitation). The test substance is added after this ageing period. This is the most widespread form of acclimation. The second process is restricted to the METI protocol (OECD 301C) and involves an extensive period of pre-culturing. Inocula are derived from at least ten sources and are blended. The rationale for using more then ten sites is to maximise microbial biodiversity. This composite inoculum is then fed daily with supplements of glucose, peptone and phosphates for a minimum period of one-month prior to use. The impacts of ageing periods on the composition and distribution of marine inocula have been extensively examined using flow cytometry. These have demonstrated large shifts in the microbial community composition. Consequently, acclimation or ageing periods impose a distinct selective pressure, which in turn may impact the outcome of subsequent biodegradability assessments thus increasing the uncertainty in the extrapolation of laboratory biodegradation test data to the environment. The data presented in this study demonstrates the impact acclimation has on the composition of a marine inoculum and highlights experimental approaches to minimise these population shifts.
Key words: Persistence, exposure assessment, degradation, marine