Potential of Trametes maxima IIPLC-32 derived laccase for the detoxification of phenolic inhibitors in lignocellulosic biomass prehydrolysate

Lignin derived inhibitors have a detrimental effect on biomass hydrolysis making the use of lignocellulosic biomass irrelevant at industrial scale. Laccase mediated removal of inhibitors has generated significant interest owing to its wide range of substrate specificity, low cost and environment-friendly nature making it an appropriate choice for the biotechnology industry. In the present work, a white rot fungal strain isolated from decaying wood samples was characterized for laccase production using a dual screening approach with ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate)) and methylene blue as substrates. Extracellular laccase was purified from this strain using anion exchange chromatography and observed to have molecular mass of 70 kDA. The UV-vis spectra of the purified enzyme confirmed blue type laccase. The enzyme exhibited stability in the pH range 2-5 and temperature of 50-70 degrees C with ABTS. The enzyme also displayed elevated level of tolerance to inhibitors like sodium azide and dithiothreitol. Purified laccase showed Km and Kcat value of 59.73 mu M and 1168 sec(-1) respectively with ABTS and 16.29 mu M, 84.3 sec(-1) using syringaldazine as substrate respectively. The 0.1U/ml of Trametes maxima HPLC-32 laccase removed 66% of lignin-derived soluble phenolic inhibitors from sugarcane bagasse within half hour at 5.5 pH. These properties indicate a high potential of Trametes maxima IIPLC-32 laccase for industrial applications.