A halotolerant laccase from Chaetomium strain isolated from desert soil and its ability for dye decolourization

Abstract

A novel fungal laccase produced by the ascomycete sp. isolated from arid soil was purified and characterized and its ability to remove dyes was determined. Extracellular laccase was purified 15-fold from the crude culture to homogeneity with an overall yield of 50% using ultrafiltration and anion-exchange chromatography. The purified enzyme was found to be a monomeric protein with a molecular mass of 68 kDa, estimated by SDS-PAGE, and with an isoelectric point of 5.5. The optimal temperature and pH value for laccase activity toward 2,6-DMP were 60 °C and 3.0, respectively. It was stable at temperatures below 50 °C and at alkaline conditions. Kinetic study showed that this laccase showed higher affinity on ABTS than on 2,6-DMP. Its activity was enhanced by the presence of several metal ions such as Mg, Ca and Zn, while it was strongly inhibited by Fe, Ag and Hg. The novel laccase also showed high, remarkable sodium chloride tolerance. Its ability to decolorize different dyes, with or without HBT (1-hydroxy-benzotriazole), as redox mediator, suggests that this protein may be useful for different industrial applications and/or bioremediation processes.

Purification and characterization of a fungal laccase from the ascomycete Thielavia sp. and its role in the decolorization of a recalcitrant dye

“…After 3 days of growing on a rotary shaker (160 rpm) at 40 °C, the mycelial pellets were harvested and 5 mL were used as inoculum for further experiments. The growth medium was prepared according to Mtibaà et al [16]. Submerged cultures were incubated at 40 °C with shaking at 160 rpm and samples were taken periodically.…”

“…Enzyme activity was estimated by monitoring the absorbance change at 436 nm for 5 mM ABTS oxidation (ƐABTS = 29,300 M −1 cm −1 ) [17] and at 469 nm for 5 mM 2,6-DMP oxidation (ƐDMP = 27,500 M −1 cm −1 ) [16] in 0.1 M Britton-Robinson buffer, pH 5.0 at room temperature.…”

“…This result was in the range of typical fungal laccases which were characterized by optimum temperature activity between 50 -80 °C [25,33,34]. Similar optimum temperatures were obtained with 2,6-DMP by some ascomycetes laccases from M. albomyces (60-70 °C), Chaetomium sp., and the white rot fungus Abortiporus biennis (60 °C) [16,23,35].…”

“…Xylogone sphaerospora (IC50 for 200 mM) and Sinorhizobium meliloti (70% inhibition for 1 mM) [16,33]. Safary et al [3] suggest that this inhibition is due to the binding of chloride ions…”

Linking Enzymatic Oxidative Degradation of Lignin to Organics Detoxification

“…The Chaetomium sp. laccase was able to decolorize the anthraquinonic dye RBBR (Remazol brilliant blue R) [ 71 ].…”