Degradation of cresols by phenol-acclimated aerobic granules

High-strength cresol isomers were treated with phenol-acclimated granules in batch experiments. The aerobic granules effectively metabolized cresol isomers at concentrations up to 1,500 mg l−1. The modified Haldane kinetic model, used to assess the kinetic behavior during cresol degradation by granule cells, yielded a high maximum specific growth rate (1.13–1.45 h−1) and inhibition constant (617–952 mg l−1). The microbial community structure, which was stable under cresol stress, was principally composed of genera Bacillus, Acinetobacter, Corynebacterium, and Nocardioides. Enzyme assay results suggest simultaneous expression of ortho- and meta-cleavage pathways during cresol degradation. Under high cresol concentrations, however, cresol isomers were largely degraded via the meta-cleavage pathway, likely attributable to the activity of Bacillus. The aerobic granular sludge system is a promising biotechnology for degrading wastewater containing high-strength cresols.