Isolation and screening of yeast strains possessing synthetic dye decolorizing activity

Results Materials and Methods Four commercial dyes were used — Remazol® Black BA, Levafix® Blue Ca, Levafix® Yellow CA and Levafix® Red CA (Dystar). A standard anthraquinone dye, Remazol Brilliant Blue R (RBBR, Sigma) was also used. Dye stock solutions were added to solid or liquid decolorization media, up to 200 mg.L-1 final concentration. Rose Bengal Agar and Potato Dextrose Agar (both from Difco) were used for yeast isolation and maintenance. Normal Solid Decolorization Media (NSDM) and Normal Liquid Decolorization Media (NDM) were prepared, as described by Pajot et al. (2007), and used for decolorization assays. Yeast strains were isolated from wastewater samples collected at biological treatment and homogenization tanks, from two wastewater stations receiving textile effluents. Newly isolated yeasts, as well as a few ones isolated previously from cheese were evaluated for decolorization ability in in NSDM at 30 oC, along 48 h. Three isolates were selected for further evaluation of decolorization ability in NDM at 30oC (120 rpm) for 72 h. Synthetic dyes — although extensively used in several industrial sectors, due to their aromatic moieties, are often highly recalcitrant. Furthermore dyes can cause considerable environmental pollution, so their removal has received considerable attention. A few microorganisms have been found that can degrade dyes; including filamentous fungi due to their extracellular enzyme systems (Moreira et al., 2001). Yeasts, however, possess the advantage of growing faster than filamentous fungi, and some can easily resist to adverse environments. Nevertheless, degradation of synthetic dyes by yeasts has not been extensively studied to date.