Chiang Mai Journal of Science

Ligninolytic white-rot fungi produce ligninolytic enzymes such as laccase, lignin peroxidase and manganese peroxidase. Biotechnological application of these enzymes for decomposition of lignocellulose is desirable. This research focused on identifying new strains of edible white-rot fungi demonstrating efficient production of ligninolytic enzymes, specifically lignin peroxidase/manganese peroxidase (LiP/MnP), polyphenoloxidase (PPO) and laccase (Lac). Seventy-seven edible white-rot fungal strains, including isolates obtained from culture collections and commercial markets were initially assessed for their production of ligninolytic enzymes according to enzymatic index (EI) from agar plate screening assays. Among the tested strains, 20 (25.97% of all edible white-rot strains), 70 (90.90%) and 73 strains (94.81%) demonstrated LiP/MnP, PPO and Lac activity respectively, with EI ranging 0.3 –1.0, 0.2 – 4.4, and 0.9 – 49.2, respectively. Three strains of Pleurotus sp. (FF00812, FF00816 and FF00826) showed the highest EI for LiP/MnP (EI = 1.0), whereas Hericium erinaceus FF00836 showed the highest Lac activity (EI = 49.2). Although Termitomyces sp. BCC26638 was the best producer of PPO, this fungus was a very slow-growing strain; as a result, this taxon was replaced by Termitomyces sp. BCC20826, which is a three-enzyme producer of LiP/MnP, PPO, and Lac. Enzyme activities for five selected edible white-rot strains were quantitatively evaluated in submerged fermentation. Pleurotus sp. FF00816 showed the highest activities of LiP, MnP and Lac, at 8695.6, 2064.5 and 9277.0 Units/liter (U/L), respectively. Based on their 28S rDNA and ITS DNA sequences, the isolated strains were confidently identified as P. pulmonarius (FF00812, FF00816 and FF00826), T. cylindricus (BCC20826) and H. erinaceus (FF00836). This work demonstrates the ligninolytic enzyme-producing potential of five strains, with the possibility for further development of industrial application in the future.