O potencial de Priestia megaterium na degradação da benzofenona-3

Abstract

This study evaluated the biotechnological potential of the Gram-positive bacterium Priestia megaterium CCT 2478 for the biodegradation of the sunscreen agent Benzophenone-3 (BP-3), a recalcitrant and lipophilic emerging contaminant that pollutes aquatic and agricultural ecosystems due to its inefficient removal in wastewater treatment plants. The aim of this study was to investigate the ability of this bacterial strain to degrade the pollutant, proposing a sustainable bioremediation strategy for agricultural and environmental matrices. Initially, the bacterial strain was cultivated in Tryptic Soy Broth (TSB) at 30 °C for 48 h and standardized to 1 × 10⁸ CFU mL⁻¹ to be used as the initial inoculum. A 200 mg L⁻¹ BP-3 stock solution was prepared in UV/HPLC-grade methanol. A supplemented mineral salt medium containing yeast extract and sodium nitrate was used as the culture medium for the biodegradation assays. To evaluate BP-3 degradation, two experimental systems were prepared: a control sample containing culture medium and BP-3 at a concentration of 15 mg L⁻¹, and a treated sample containing culture medium, BP-3 at 15 mg L⁻¹, and P. megaterium at 1 × 10⁷ CFU mL⁻¹. Both the control and treated samples were incubated at 30 °C under orbital agitation at 150 rpm for 144 h. BP-3 quantification was performed using high-performance liquid chromatography (HPLC) equipped with an ACE deactivated-base RP-18 column (250 × 4.6 mm, 5 μm particle size, 100 Å pore size, and 15.5% carbon loading) as the stationary phase. The mobile phase consisted of methanol and ultrapure water acidified with 0.5% acetic acid in a 90:10 (v/v) ratio. After injection of 50.0 μL of the sample, chromatographic separation was carried out under isocratic conditions at a flow rate of 1.0 mL min⁻¹, with the column maintained at 40 °C and detection performed at a wavelength of 288 nm. The results showed that monitoring of the supernatant fraction revealed a slight reduction of approximately 6% in BP-3 concentration compared with the control group. It was concluded that the observed decrease was not attributable to active microbial biodegradation, owing to the high chemical stability of the compound. As a recalcitrant organic contaminant, BP-3 presents limitations associated with the lack of prior acclimatization of the bacterial strain to the sunscreen compound and possible inhibitory effects resulting from cellular toxicity at the tested concentration. Therefore, future investigations should evaluate co-metabolic systems and the gradual acclimation of the bacterium to lower concentrations of Benzophenone-3 to enhance its biodegradation potential.