Isolation and screening of extracellular enzymatic activity of endophytic fungi isolated from Thai orchids

Abstract

Endophytes living inside plant tissues are known to be a rich source of unique bioactive compounds. In the current study, endophytic fungi were isolated from the leaves, stems and roots of five species of epiphytic orchids: Doritis pulcherrima, Dendrobiuma phyllum, Dendrobium anosmum, Ascocentrum curvifolium and Aerides falcata. In total, 52 endophytic isolates were obtained from the orchid samples, with the most (27) being obtained from leaf segments followed by roots and stems. All of the endophytic isolates were assessed for their potential role in producing extracellular enzymes, including amylase, protease, cellulase, pectinase and lipase on solid media. The results showed that 67%, 56%, 49%, 39% and 25% of the endophytic isolates had the ability to produce lipase, cellulase, pectinase, protease and amylase enzymes, respectively. One endophytic isolate, DapR 02, isolated from the root of Dendrobium aphyllum produced significantly more pectinase enzyme secretion with a ratio of the clear zone diameter to the colony diameter of 23. It was identified as Pseudopestalotiopsis theae using morphological characteristics and molecular analysis. This was the first report of the pectinase enzyme production potential of the endophyte Pseudopestalotiopsis theae. Therefore, an experiment was conducted to optimize the pectinase production in the DapR 02 isolate. High pectinase production of 1.524 U/mL was observed under culture conditions of 30 °C and pH 3.