Optimization, purification and characterization of laccase from a new endophytic Trichoderma harzianum AUMC14897 isolated from Opuntia ficus-indica and its applications in dye decolorization and wastewater treatment.

Abstract

Hazardous synthetic dye wastes have become a growing threat to the environment and public health. Fungal enzymes are eco-friendly, compatible and cost-effective approachfor diversity of applications. Therefore, this study aimed to screen, optimize fermentation conditions, and characterize laccase from fungal endophyte with elucidating its ability to decolorize several wastewater dyes. A new fungal endophyte capable of laccase-producing was firstly isolated from cladodes of Opuntia ficus-indica and identified as T. harzianum AUMC14897 using ITS-rRNA sequencing analysis. Furthermore, the response surface methodology (RSM) was utilized to optimize several fermentation parameters that increase laccase production. The isolated laccase was purified to 13.79-fold. GFC, SDS-PAGE revealed laccase molecular weight at 72kDa and zymogram analysis elucidated a single band without any isozymes. The peak activity of the pure laccase was detected at 50°C, pH 4.5, with thermal stability up to 50°C and half life span for 4h even after 24h retained 30% of its activity. The Km and Vmax values were 0.1mM, 22.22µmol/min and activation energy (Ea) equal to 5.71kcal/mol. Furthermore, the purified laccase effectively decolorized various synthetic and real wastewater dyes. Subsequently, the new endophytic strain produces high laccase activity that possesses a unique characteristic, it could be an appealing candidate for both environmental and industrial applications.