Effect Produced by a Mixture of Phenol, p-Cresol, and Acetophenone on Four Species of Microalgae: Tolerance, Biodegradation, and Metabolic Alterations

Abstract

Phenol-derived compounds are among the most hazardous organic pollutants for aquatic environments due to their relatively high aqueous solubility. Microalgae harbor metabolic pathways that enable the degradation of phenolic compounds into less toxic derivatives, highlighting their potential for the bioremediation of these contaminants. In this study, four microalgal species were evaluated for their tolerance and biodegradation capacity of a mixture of phenolic compounds which include phenol, p-cresol, and acetophenone. The results revealed that Chlorella sorokiniana and Nannochloropsis gaditana could tolerate higher concentrations of the mixture (60, 50, and 25 mg L−1 of phenol, p-cresol, and acetophenone) than Chlamydomonas reinhardtii and Tetraselmis chuii (60, 30, and 20 mg L−1 of phenol, p-cresol, and acetophenone). Notably, Tetraselmis chuii could biodegrade these compounds with the highest efficiency (32, 45, and 85% of initial phenol, p-cresol, and acetophenone, respectively) after 72 h of cultivation. In the absence of alternative carbon sources in the medium, Tetraselmis chuii also biodegraded 45, 60, and 51% of initial phenol, p-cresol, and acetophenone, at 72 h, highlighting its potential for bioremediation processes. Finally, the ascorbate peroxidase, catalase, and phenol hydrolase enzymatic activities of Tetraselmis chuii were studied in presence of the pollutants, showing increasing activity levels of these enzymes (123, 135, and 173% of control cultures for APX, CAT, and PH, respectively) involved in the antioxidant system and the degradation of phenolic compounds.