Phenol biodegradation by the thermoacidophilic archaeon Sulfolobus solfataricus 98/2 in a fed-batch bioreactor

Toxic at low concentrations, phenol is one of the most common organic pollutants in air and water. In this work, phenol biodegradation was studied in extreme conditions (80°C, pH = 3.2) in a 2.7 l bioreactor with the thermoacidophilic archaeon Sulfolobus solfataricus 98/2. The strain was first acclimatized to phenol on a mixture of glucose (2000 mg l(-1)) and phenol (94 mg l(-1)) at a constant dissolved oxygen concentration of 1.5 mg l(-1). After a short lag-phase, only glucose was consumed. Phenol degradation then began while glucose was still present in the reactor. When glucose was exhausted, phenol was used for respiration and then for biomass build-up. After several batch runs (phenol < 365 mg l(-1)), specific growth rate (μ(X)) was 0.034 ± 0.001 h(-1), specific phenol degradation rate (q(P)) was 57.5 ± 2 mg g(-1) h(-1), biomass yield (Y(X/P)) was 52.2 ± 1.1 g mol(-1), and oxygen yield factor (Y(X/O2)) was 9.2 ± 0.2 g mol(-1). A carbon recovery close to 100% suggested that phenol was exclusively transformed into biomass (35%) and CO(2) (65%). Molar phenol oxidation constant (Y(O2/P)) was calculated from stoichiometry of phenol oxidation and introducing experimental biomass and CO(2) conversion yields on phenol, leading to values varying between 4.78 and 5.22 mol mol(-1). Respiratory quotient was about 0.84 mol mol(-1), very close to theoretical value (0.87 mol mol(-1)). Carbon dioxide production, oxygen demand and redox potential, monitored on-line, were good indicators of growth, substrate consumption and exhaustion, and can therefore be usefully employed for industrial phenol bioremediation in extreme environments.