Screening and Identification of Cellulase Producing Yeast from Rongkho Forest, Ubon Ratchathani University

Abstract

In this present study, a total of 82 yeast strains were obtained from 111 samples collected from various sources such as soil, tree barks and insect frass from RongKho forest, Ubon Ratchathani University. They were screened and identified for cellulase production. Based on their capabilities of degrading carboxymethyl cellulose as a sole carbon source in solid medium, 45 strains performed cellulose hydrolysis which was verified by the colorless halo in the solid medium. Among them, 3 strains namely UBU-SK6, UBU-JK8 and UBU-JK9/1 showed higher levels of enzyme activity. After the step of solid medium selection, yeast cells were grown in liquid medium containing 1% yeast extract and different concentration of carboxymethyl cellulose (0.5-1.5%) under shaking with 150 rpm at 30°C and for 168 h. The enzyme activity of these 3 strains exhibited 0.224, 0.238 and 0.26 UmL-1 , respectively. Afterwards, these wild yeast strains were molecularly identified by sequencing the ITS1-5.8S-ITS2 and D1/D2 domains of the subunit (26S) ribosomal DNA. The identification of UBU-SK6, UBU-JK8 and UBU-JK9/1 showed 98-100% similarity as Candida sp. 05-7-186T, Candida easanensis and Candida sp. ST-390 respectively.