Supplemental Material for Arrey et al., 2021
Bioconversion of hemicelluloses into simpler sugars leads to production of a significant amount of pentose sugars, such as D-xylose. However, efficient utilization of pentoses by conventional yeast production strains remains challenging, especially due to inhibition by hexose co-fermentation. Wild yeast strains can provide new industrially relevant characteristics to bypass these inhibitions and efficiently utilize pentose sugars. To explore this strategy, we isolated gut-residing yeasts from the termite Macrotermes bellicosus collected in Comoé National Park, Côte d´Ivoire. The yeasts were classified through their ITS and LSU sequence and genomes of three new strains and species were sequenced and annotated. We identified a novel yeast species, which we name Barnettozyma botsteinii sp. nov. 1118T (MycoBank: 833563, CBS 16679T and IBT 710) and two new strains of Kurtzmaniella quercitrusa: var. comoensis (CBS 16678, IBT 709) and var. filamentosus (CBS 16680, IBT 711). The two K. quercitrusa strains grow 15% faster on synthetic glucose medium than Saccharomyces cerevisiae CEN.PKT in acidic conditions (pH = 3.2) and both strains grow on D-xylose as the sole carbon source at a rate of 0.35 h-1. At neutral pH, the yeast form of K. quercitrusa var. filamentosus, but not var. comoensis, switched to filamentous growth in a carbon source dependent manner, revealing phenotypic diversity among strains within the species. The utilisation of plant-derived sugars by K. quercitrusa indicates the potential for a mutualistic relationship between this yeast and the termite. Besides its metabolism, K. quercitrusa var. filamentosus also has a large potential as a production organism, because of its capacity to grow at low pH and to undergo a dimorphic shift.
