Isolation, identification and screening of lignocellulose-degrading fungi from sediments and seawater in mangrove forest at Laemson National Park, Thailand

Abstract

The aims of this study were to isolate, screen and identify cellulose, hemicellulose and lignin-degrading fungi obtained from sediment and seawater samples collected from three sub-zones located in Andaman Coastal Research Station for Development, Laemson National Park, Thailand. In laboratory, fungal stains were isolated using a serial dilution method on Potato Dextrose Agar (PDA). All isolated fungi were identified by sequence comparison using ITS rDNA region, and classified according to the characteristics of fungal colonies. Based on their different colony morpho-types and molecular data, a total of 193 fungal strains classified into 3 phyla, 4 classes, 9 orders, 13 families, 56 genera and approximately 88 species were isolated from Zones 1, 2 and 3 with 34.20%, 34.72% and 31.09%, respectively (or 67% derived from sediment and 33% from seawater samples based on substrate origin). Of these, the most frequently encountered genera were Penicillium (21.24%), Trichoderma (19.17%), Aspergillus (8.29%), Fusarium (7.25%) and Scedosporium (3.63%). All fungal strains were preliminarily screened, based on their different abilities to form the clear zones around the fungal colonies on carboxymethyl cellulose (CMC) agar for cellulase, and on xylan media for xylanase activities. In addition, these fungal strains were also tested on three selected media, which were Azino-ethylbenzothiazoline sulfonic-acid diammonium salt (ABTS) agar, Azure-B agar and Tannic acid agar for laccase, peroxidase and polyphenoloxidase activities, respectively. Fifty-nine, 98, 111, 14, and 6 fungal strains were indicated for the presences of cellulase (30.57%), xylanase (50.78%), laccase (57.51%), peroxidase (7.25%) and polyphenoloxidase (3.11%), respectively. Seventeen out of 193 strains with the potential to produce three lignocellulosic enzymes (8.81%), including cellulase, xylanase and ligninolytic enzymes were identified as the follows: Acremonium sp. ASP00065, Acremonium sp. ASP00511, Aspergillus fumigatus ASP00199, A. niger ASP00108, A. tubingensis ASP00113, Biscogniauxia mediterranea ASP00508, Ceratocystis paradoxa ASP00125, Ceriporia lacerata ASP00195, Paraconiothyrium sp. ASP00509, Penicillium funiculosum ASP00234, P. purpurogenum ASP00063, Penicillium sp. ASP00129, Pestalotiopsis adusta ASP00087, Polyporus brumalis ASP00206, Scedosporium apiospermum ASP00034, Talaromyces funiculosus ASP00139, and Theleporus membranaceus ASP00207. As the best enzymatic producers, Aspergillus nutans ASP00245 had the highest cellulase activity (18 mm), and the maximum xylanase activity of 31.3 mm was shown by Talaromyces purpureus ASP00503. Moreover, the maximal activities on laccase, peroxidase and polyphenoloxidase were found on Trichaptum biforme ASP00198 (100.0 mm), Gymnascella hyalinospora ASP00519 (16.4 mm) and Viridispora sp. ASP00196 (16.0 mm), respectively. In this study, the results suggest that fungal strains derived from Andaman Coastal Research Station for Development and their fungal screenings might be interesting source of lignocellulose enzymatic potential. However, more studies should be performed in future based on enzyme production and optimization conditions i.e. pH, temperature, culture and media compositions.