Improving structure-biodegradation relationships to predict products and rates of aerobic biotransformation of organic micropollutants

Abstract: Biotransformation of organic contaminants by mixed microbial communities in soils, sediments or activated sludge is a major determinant of the environmental fate of many chemicals. Since the experimental investigation of the biodegradation potential for all chemicals in commerce, let alone their transformation products, is not feasible, methods to predict biodegradation potential and pathways as a function of molecular structure alone have been sought for. However, existing so-called (quantitative) structure-biodegradation relationships to predict rates and products of microbial transformation are impacted with large uncertainties. In this project, we therefore explore the possibility to improve the accuracy of predicting rates and products of aerobic, microbial transformations

(i) given a sufficiently large and consistent set of biotransformation data,

(ii) by exploiting information on observed transformation products, and

(iii) by restricting the predictions to represent a specific, relevant system for biotransformation of contaminants, i.e., aerobic activated sludge treatment.

To this end, we will first experimentally investigate the biodegradation pathways of prevalent types of compounds, i.e., amines, ethers and different ester derivates, in sludge-seeded bioreactors using high-resolution mass spectrometry for product identification. Second, we will use chemoinformatic and molecular modeling approaches to link observed transformation pathways and rates with structural information. The outcomes of this project will be implemented into an existing computer-based, publically available system to predict biotransformation pathways (http://umbbd.ethz.ch/predict/index.html). The revised system should exhibit an increased selectivity and accuracy in predicting biotransformation pathways and should include a new module for estimating biotransformation rates during activated sludge treatment.

Project collaborators: Rebekka Gulde, Damian Helbling, Kathrin Fenner