Application of the computer-automated structure evaluation (CASE) program to the study of structure-biodegradation relationships of miscellaneous chemicals

The computer-automated structure evaluation (CASE) methodology has been used to investigate the correlation between chemical structure and rate of biodegradation. A training set consisting of 283 diverse organic chemicals of known biodegradation activity was evaluated. Computer-automated structure evaluation identified six major activating fragments that contained oxygen in a carbonyl or hydroxyl group, suggesting that the presence of oxygen plays a significant role in biodegradation. The training set predicts the biodegradation categories correctly 74% of the time for an independent validation set of 27 chemicals. By also using a data base of diverse chemicals whose activity was based on acclimated inocula, two prediction results were obtained for each of the 27 chemicals of an independent validation set. Analysis of the results showed that the chemicals could be grouped into five prediction categories. Two of these categories included chemicals for which both data bases predicted exactly the same activity, whereas a third category contained two chemicals for which no conclusion was made. The other two categories include chemicals of intermediate activity, that is, chemicals that can undergo slow or fast biodegradation, depending on the conditions. In addition, the identification of activating structural fragments has provided information on mechanisms for biodegradation in the environment.