Laccase Production from White Rot Fungi and Immobilization on Nano Particles

Demarche, Philippe [UCL] Nair, Rakesh [UCL] Junghanns, Charles [UCL] Agathos, Spiros N. [UCL]

White rot fungi (WRF) are considered to be most promising among eukaryotic microorganisms that degrade lignin because they are the best known producers of extracellular oxidases, particularly lignin peroxidases, manganese peroxidases and laccases. Due to their broad substrate specificity, this group of enzymes has great biotechnological potential in diverse fields of industrial applications such as in pulp delignification, textile dye bleaching, wastewater treatment and xenobiotic detoxification. Laccases are multi-copper oxidases that catalyze the oxidation of a variety of phenolic substances coupled to the reduction of oxygen to water. Recently there has been a growing interest in studying a wider array of white rot fungi with the expectation of finding fungal laccases capable of degrading several xenobiotics of environmental concern, e.g. polycyclic aromatic hydrocarbons. In this study, different promising genera of WRF such as Coriolopsis, Trametes, Ganoderma and Pycnoporus were screened and evaluated based on maximal laccase production, thermal stability and capability to detoxify endocrine disruptors. From the above studies Coriolopsis polyzona was found to be the best candidate producing laccase activity levels of 100 U/mL. In parallel, based on previous studies of laccase immobilization by Cabana et al. 2009, three different silica particles at millimeter, micrometer and nanometer scale were tested for effective laccase binding and stability. There are several advantages of using immobilized enzyme over free enzyme as it enhances process robustness and re-use of the biocatalyst in multiple cycles. The results showed an enhanced recovery of 100% laccase activity using nano particles compared to 25% and 3% that was observed with micro and macro particles respectively. The improved stability of the novel biocatalyst against temperature, pH and mechanical stress, provided by immobilization is under study. The results will be exploited in future studies endeavoring an application of the immobilized particles in continuously operated membrane reactors for the biotransformation of micropollutants such as bisphenol A, triclosan etc.