Decolorization of different synthetic dyes by two Trametes strains and Pleurotus ostreatus ATCC 58053, and their laccase and manganese peroxidase activity

Abstract

Polyurethanes (PUs) are plastics which are used as raw material in several industries. This xenobiotic substance has been used as adhesive, flexible foam, elastomer, covering, etc. It is made from a diol and a diisocyanate and it is classified as polyether or polyesther PU. Given its versatility, its production has increased and has brought the problem of its disposal. The actual strategies include burning and recycling. However, there is recent interest in the search of a biological alternative for the degradation of PU, using microorganisms or their enzymes involved in the mechanisms implied in this process. It has been reported that polyesther PU are more susceptible to microbial attack and this has been attributed to enzymes with protease, esterase and urease activities. The major part of the research of biological degradation of PU focus in the use of bacteria such as Pseudomonas, Comamonas and Bacillus, however there is very little information in the use of molds. The aim of this work was to find molds capable of using PU as sole carbon source and to determine if they showed any of the enzymatic activities mentioned before. Molds were isolated of sand samples contaminated with PU and were cultured in a minimal medium with PU as sole carbon source. Also, the molds were cultured in the resins used for the synthesis of the plastic. The strains were incubated at 30 • C for seven days and the molds capable of growing in the medium were preserved to their later study. Also, strains from the collection of our research group were tested following the same protocol. The fungal strains that grew using PU as sole carbon source were cultivated in specific media for the detection of protease, urease and esterase activities and were also incubated at 30 • C for seven days. Several molds were capable of growing on one or both of the resins used for the synthesis of PU, but not all of the molds that grew on the resins, grew on the plastic. Among the genera that grew using PU were Alternaria, Aspergillus and Paecelomyces and 20 fungal strains grew using it. All of the 20 showed protease activity, 19 showed urease activity and only 11 of them showed esterase activity. This study reveals that several fungi have the ability of using PU as sole carbon source exhibiting several enzymatic activities associated with PU hydrolysis.It has been well known that white rot fungi could be used to decolorize textile dye effluents and the involved laccases and peroxidases play an important role in the process. The objective of this work was to study the ability of two native basidiomycetes strains of the genus Trametes (RVAN2 and RVAN12), cultivated in wheat bran medium to decolorize five different synthetic dyes and measure their enzymatic activity of lacasse and manganese peroxidase enzymes. As a control, Pleurotus ostreatus ATCC 58053 was used. The probed colorants were Brilliant Green, Crystal Violet, at 15 mg, and RBBR, Indigo Carmine, Methylene Blue, at 30 mg. During fermentation, newly aliquots of dyes were added when the decoloriza...