Biodecolorization of Six Synthetic Dyes by Pleurotus ostreatus ARC280 Laccase in Presence and Absence of Hydroxybenzotriazole (HBT)

Aim: The aim of the present study was to investigate the potential effect of laccase enzyme produced by the fungus Pleurotus ostreatus to decolorize six synthetic dyes in presence and absence of hydroxybenzotriazole (HBT) as a laccase mediator.

Study Design: Qualitative and quantitative evaluation for the efficiency of laccase produced by Pleurotus ostreatus to decolorize six tested dyes in the presence and absence of HBT.

Place and Duration of Study: Department of Microbial Chemistry, Genetic Engineering and Biotechnology Division, National Research Centre (NRC), Cairo, Egypt, between April 2016 and May, 2017.

Methodology: Pleurotus ostreatus ARC280 was maintained on Potato Dextrose Agar (PDA) medium and kept at 4ºC. Production of laccase was preceded by growing Pl. ostreatus on liquid media under static conditions. The efficiency of laccase obtained from P. ostreatus ARC280 on dyes decolorization was determined by the decrease in absorbance at the maximum wavelength of each dye. The efficiency of decolorization was expressed in terms of decolorization percentage.

Results: Results obtained showed that the enzyme was efficient in decolorizing Acid-Green 27 (95.33%), Acid dye Lanapel Red BM 143-PL (100%) and Congo Red (72.76%) at dye concentration of 25 mg/l; enzyme units, 0.657 U and after 6 h of incubation at 30ºC. In the presence of HBT (1 mM), the time required for reaching 100% decolorization of Acid Green-27 and Acid dye Lanapel Red BM 143-PL was reduced to the half. Absorbance reduction at the maximum wavelength was recorded with all the tested dyes indicating the efficiency of the decolorization process.

Conclusion: The results obtained indicated the effectiveness of P. ostreatus ARC280 laccase and its mediated system in the decolorization of six structurally different dyes. Addition of HBT decreased the time required to reach the maximum decolorization percentage of Acid-Green 27 and Acid dye Lanapel Red BM 143-PL to the half. The decolorization percentage of Cibacron D-Blue was greatly affected by HBT-laccase mediator system by about 45% increase.