Screening of eucalyptus wood endophytes for laccase activity

Abstract

New lignin-degrading microorganisms and their enzymes can contribute to more efficient and environmentally sound use of lignocellulosic biomass in future biorefineries. In view ofthis, 127 endophytic fungi were isolated from eucalyptus trees. Strains were tested for their ability to produce ligninolytic enzymes in agar-plate medium containing ABTS, and 21 showed positive ABTS-oxidation. Positive strains in liquid medium confirmed that five produced laccase but no peroxidase activity. These strains were identified as Hormonema sp. and Pringsheimia smilacis, of the family Dothioraceae, Ulocladium sp. (Pleosporaceae) and Neofusicoccum luteum and Neofusicoccum australe (Botryosphaeriaceae). Laccase production by fungi of the family Dothioraceae is described here for the first time.To increase laccase production from these fungi, copper sulphate and ethanol were assayed as inducers. An increase in laccase activity of 85% was found for Hormonema sp. and N. luteum and 95% for N. australe. No increase was obtained for P. smilacis. A maximum temperature of 40 ◦C is recommended for possible biotechnological applications with these four strains at pH 2 for N. luteum and N. australe, pH 4 for Hormonema sp. and pH 4–5 for P. smilacis.