A preliminary study on the biosorption characteristics of Trichosporon akiyoshidainum HP-2023 for reactive textile dyes.

PAJOT, HIPÓLITO F; ROVATI, JOSÉ I; FARIÑA, JULIA I; FIGUEROA, LUCÍA IC

Kyiv, Ukraine

Congreso; ICY2008, 12th International Congress on Yeasts; 2008

International Comission for Yeasts

Synthetic dyes are extensively used in many fields of up-to-date technology, e.g., textile industry, leather tanning industry, paper production, food technology, etc. Traditional wastewater treatment technologies have proven to be markedly ineffective for handling wastewater of synthetic textile dyes mainly, because of the chemical stability of these pollutants. The growing impact of environmental protection on industrial activities promotes the development of ecofriendly technologies for the removal of synthetic dyes from waters and wastewaters to decrease their impact on the environment. Classical physico-chemical treatments usually involve adsorption on inorganic or organic matrices, decolorization by photocatalysis, and/or by oxidation processes. Biological processes such as biosorption or enzymatic decomposition have been already proposed as having potential application in the removal of textile wastewater dyes. In particular, when microbial cultures are used, both these mechanisms have been ascribed to biodecolorization, either separately or through concerted action. The possibility to investigate the contribution of each mechanism to dye removal would be particularly valuable in order to design and optimize an efficient biological treatment. This work deals with the biosorption capacity of living and heat-killed biomass of Trichosporon akiyoshidainum HP-2023 for two reactive textile dyes, Vilmafix® Blue RR-BB and Vilmafix® Red 7B-HE. T. akiyoshidainum HP-2023 was previously selected because of its ability to remove up to 200 mg/l of each tested dye after 36 h of cultivation in liquid Normal Decolorization Medium (NDM), even at pH 7.0. In order to elucidate the contribution of biosorption processes to the decolorization capacity of this yeast, the Qeq (adsorbed dye quantity per gram of biomass at equilibrium, mg/g) and optimum initial sorption pH were assessed for both tested dyes. Biosorption of tested dyes was maximal at pH 1.0, either when contacted with live or heat-killed yeast biomass. Likewise, for Vilmafix® Blue RR-BB and heat-killed biomass, biosorption showed to be higher. Qeq values were strongly affected by pH, dye nature and biomass status, ranging from 8 to 59 mg of dye per g of biomass. The results presented here can probably indicate the existence of two mechanisms in the decolorization process: a first fast step of biosorption, followed by a later step where some different metabolites (either enzymatic or not) may be involved.