Biodegradation of phenol by Penicillium chrysogenum: degradation abilities and kinetic model

DURRUTY, I.; HAURE P. M.; GONZALEZ J.F.; WOLSKI E. A

Tucumán

Congreso; CONGRESO ARGENTINO DE MICROBIOLOGÍA GENERAL SAMIGE DEL BICENTENARIO (SAMIGE).; 2011

SAMIGE

Phenol is one of the most common organic water pollutants, usually present in the industrial wastewater generated by the production of resins, petroleum refinery and petrochemicals.   Various techniques are used for the elimination of phenol present in aqueous wastes and, among them; biotechnology methods are relevant because they have the potential to mineralize toxic compounds at a relatively low cost. Most treatments are based on the biodegradation ability of bacteria, but only a few studies have involved fungi. Most of them, using plant pathogenic fungi, which results in a high risk to the environment or fungi that have highly nutritional requirements. Strains of the genus Penicillium have been reported as good hydrocarbon-assimilating and there are many reports showing their ability to transform xenobiotic compounds into less mutagenic products. The bioremediation potential of Penicillium chrysogenum was studied in batch culture using synthetic phenol in water as the sole carbon and energy source. In order to describe the substrate biodegradation, a suitable kinetic model, which relates specific growth rate ì and the phenol concentration S, was formulated. Dynamic mass balance equations for biomass and phenol during the exponential and stationary growth phases were solved and contrasted with experimental outcomes. Degradation was performed at room temperature and without a previous acclimation period. Studies were conducted in liquid mineral salt medium supplemented with initial phenol concentration of 5, 30, 60, 200, 350 and 400 mg.l-1. The effect of initial phenol concentration on the degradation process (growth and phenol degradation) was investigated over several days. Phenol was completely degraded at different cultivation times for the different initial phenol concentrations. An inhibitory effect was observed on the specific growth and degradation rates. The growth rate was inhibited at phenol concentrations higher than 30 mg.l-1, while the degradation rate was inhibited at 200 mg.l -1. Several mathematical models have been developed to quantify inhibitory effects of toxic substrates on microbial growth kinetics. Therefore, experimental results were fitted to Haldane, Yano, Aiba, Webb and Teissier models using least squares fitting method analysis. Among the five inhibition models tested, the Haldane model was found to give the best fit. Calculated kinetic values for ìmax, KS, and KI were: 1.306 ± 0.200 d-1, 9.434 ± 1.54 mg.l-1 and 64.912 ± 17.88 mg. l-1, respectively. These values are in agreement with literature results. The variation of the observed yield coefficient YX/S with the specific growth rate ì was represented by Pirt’s maintenance energy model. Dynamic mass balance equations for biomass and phenol were formulated and solved for different initial phenol concentrations. Model predictions are satisfactory.