Kinetics of aerobic phenol biodegradation by the acidophilic and hyperthermophilic archaeon Sulfolobus solfataricus 98/2

Biodegradation of 51–745 mg l−1 of phenol by a well-acclimatized strain of Sulfolobus solfataricus, a thermoacidophilic archaeon, was studied in batch experiments at 80 °C and pH 3.2. Phenol inhibited growth and specific degradation rates (μ and qS). Fitting the experimental growth data with the Haldane model gave the following kinetic parameters: μ* = 0.094 h−1, KS = 77.7 mg l−1, Ki = 319.4 mg l−1 (R2 = 0.950). The true μmax, calculated from μ*, was 0.047 h−1. A volumetric degradation rate (Vmax) was calculated by fitting the phenol consumption data with the Gompertz model. The value of Vmax increased with initial phenol concentration (Si) up to 14.4 mg l−1 h−1. The qS values, calculated from Vmax, were fitted with the Haldane equation, yielding qSmax of 0.110 g g−1 h−1. The yield factor (YX/S) depends on Si and reached a maximum of 0.83 g g−1 at Si = 93 mg l−1.S. solfataricus 98/2 displayed low μmax and qSmax but a good tolerance to phenol (fairly high Ki, K′iK′i, high YX/S). This ability to grow on and degrade phenol (93 mg l−1 < optimal Si < 175 mg l−1) at high temperature and low pH is unique and may be useful for removing phenol from hot acidic contaminated effluents. Other possible application could lie in the production of the enzymes involved in the key steps of phenol degradation provided the cloning of the enzymes-related genes in fast-growing mesophiles.

► Kinetics of phenol degradation at high temperature and low pH with an archaeon.
► Growth (μ) and specific degradation (qS) are inhibited by phenol.
► True μmax is half of the fitting parameter (μ*) given by the Haldane model.
► μmax and qSmax are low but inhibition constants (Ki, K′iK′i) and optimal phenol concentrations for growth and degradation rates (Sm, S′mS′m) are fairly good.
► The yield factor (YX/S) depends on phenol concentration.