IS Rhodotorula mucilaginosa LSL A COMPETENT ORGANISM TO REMOVE THE AZO DYE CONGO RED?

MUÑOZ NS; GONZALEZ PAISIO Z; LAMPA AMN; KURINA SANZ M; MAGALLANES-NOGUERA C; BONILLA JO

San Juan

Congreso; Reunion Anual de la Sociedad de Biología de Cuyo; 2023

SBC

One of the greatest impacts caused by humans lies in pollution coming from industrial activities. The textile industry generates 20 % of the wastewater discarded annually worldwide. The most recalcitrant elements in this industry are the azo dyes, which are widely used due to their versatility and resistance. Bioremediation appears as an eco-friendly and sustainable technology to treat this type of contamination, and the search for new biological systems capable to remove xenobiotics is imperative to develop efficient environmental remediation strategies. For these reasons, in this work we aimed to evaluate Rhodotorula mucilaginosa LSL as biological system to tolerate and remove the azo dye Congo Red (C32H22N6Na2O6S2, 696.66 g mol-1). The Minimum Inhibitory Concentration (MIC) of the azo dye was determined in a range from 125 to 1000 µg mL-1 by the agar dilution method with 1x105 cells mL-1 as inoculum during 72 h. The dye removal capacity was qualitatively evaluated in potato dextrose agar medium by adding Congo Red from 125 to 750 µg mL-1 at 30 °C during 16 days. Considering that some microorganisms can release toxic secondary metabolites, the phytotoxicity of R. mucilaginosa LSL cultures was evaluated. Supernatants were obtained by using resting-culture systems with Tris-HCl 50 mM pH 8.0 and distilled water as reaction media, which are widely used to develop decolorization assays in liquid cultures. Toxicity was determined using Lactuca sativa L. seeds after 120 h exposure by analyzing the Absolute Germination (GA) and the Germination Index (GI), which also takes into account the length of the radicle and hypocotyl. The MIC value was established in the range 750 µg mL-1 < MIC ≤ 875 µg mL-1. The microorganism was able to decolorize Congo Red in solid medium in all the evaluated concentrations. Supernatants obtained with Tris-HCl 50 mM pH 8.0 as reaction medium did not inhibited the germination (AG 96.67) or radicle (GI 84.47) and hypocotyl (GI 121.19) elongation of L. sativa L. When distilled water was used, germination was not affected (AG 100.00), but supernatants were toxic for radicle (GI 26.77) and moderate toxic for hypocotyl (GI 63.11). The results obtained in the present work show that R. mucilaginosa LSL is a promising organism to in depth into its azo dye removal capacities. Likewise, Tris-HCl 50 mM pH 8.0 seems to be the better reaction medium to test the dye removal in liquid cultures in the near future.