Characterization of xylose-utilizing yeasts isolated from herbivore faeces in Thailand

Abstract

A total of 39 xylose-utilizing yeast strains were isolated from herbivore faeces in Thailand. They were identified as Candida tropicalis (32 isolates), Candida albicans (1 isolate), Pichia terricola (1 isolate), Trichosporon mycotoxinivorans (2 isolates), Sporopachydermia lactativora (2 isolates) and Zygoascus meyerae (1 isolate) based on their morphological, cultural, physiological and biochemical characteristics including the sequence analysis of the D1/D2 region of the large-subunit ribosomal DNA. Thirty seven isolates could ferment xylose to ethanol. Zygoascus meyerae E23 isolated from elephant faeces produced the highest ethanol concentration (3.61 g/l after 72 h). C. tropicalis A26 isolated from cow faeces produced the highest xylitol concentration (43.79 g/l) which corresponded to 0.71 g xylitol/g xylose after 24 h. C. tropicalis A26 xylose reductase showed 98.4% identity and 99.0% similarity to C. tropicalis (ABX60132C) xylose reductase, and showed the tetra-amino acid motif (Ile-Pro-Lys-Ser) which is conserved among NADPH-dependent xylose reductase.