Assessing the textile-dye decolorization potential of psychrophilic and psychrotolerant yeasts from 25 de mayo/King George island (Antarctica)

Abstract

Antarctic environments typically present low temperatures, high solar radiation and low nutrient availability, being one of the harshestenvironments on Earth. Psychrophilic and psychrotolerant yeasts from Antarctic soils and cryoconites have adapted to such conditions,being an interesting source of new enzymes with great biotechnological potential. This work intends to prove the textile dye decolorizingpotential of 139 yeasts isolated from soil and cryoconite samples from 25 de Mayo / King George Island, Antarctica. Isolates were cultivatedin YM, and NDM (Normal Decolorization Medium) media at 15, 20 and 25°C, and classified into psychrophilic and psychrotolerantaccording to their growth profiles. Textile dye decolorization was evaluated in the same two media, plus 200 mg/L of one of fourcommercially available reactive azo dyes: Vilmafix® Blue RR-BB (CI, Reactive Blue 221), Vilmafix® Red 7B-HE (CI, Reactive Red141), Vilmafix® Black B-V (CI, Reactive Black 5), or Vilmafix® Green RR-4B (CI, Reactive Green). Plates were incubated for 72 h at15, 20 or 25°C, depending on the yeast isolate. Dye decolorization haloes and colony dyeing were recorded daily and used to select themost promising isolates. Of 139 isolates, 34% were classified as psychrophilic (growing only at 15°C) while the remaining 66% wereclassified as psychrotolerant (growing at all the assayed temperatures), irrespective of the medium assayed. Forty-five isolates producehaloes in at least one of the tested dyes in NDM, while only 40 yeast produced haloes in YM. 15 isolates were selected for further studiesIsolates A075 and Y28D produced intense haloes without colony dyeing; isolates Y67, Y70 and Y75 produced intense haloes and get dyedonly at the edge of the colonies while the remaining ten isolates, A092, A099, A104, A105, A106, A107, Y6, Y59, Y73 and Y84, producedneat haloes with a significant colorization of the entire colonies. The obtained results prove the biotechnological potential of Antarcticyeasts, raising the possibility of designing more efficient dye-decolorizing methods at low temperatures.