Quantitative structure-activity relationship study on the biodegradation of acid dyestuffs.

Quantitative structure-biodegradability relationships (QSBRs) were established to develop predictive models and mechanistic explanations for acid dyestuffs as well as biological activities. With a total of four descriptors, molecular weight (M(W)), energies of the highest occupied molecular orbital (E(HOMO)), the lowest unoccupied molecular orbital (E(LUMO)), and the excited state (E(ES)), calculated using quantum chemical semi-empirical methodology, a series of models were analyzed between the dye biodegradability and each descriptor. Results showed that E(HOMO) and M(W) were the dominant parameters controlling the biodegradability of acid dyes. A statistically robust QSBR model was developed for all studied dyes, with the combined application of E(HOMO) and M(W). The calculated biodegradations fitted well with the experimental data monitored in a facultative-aerobic process, indicative of the reliable prediction and mechanistic character of the developed model.