Growth of yeast on solid medium containing different sugars. Screening of 306 yeast strains was performed by observing their growth on YNB medium supplemented with either L-arabinose (YNA), xylose (YNX), xylitol (YNXL) or xylose mother liquor (YPX). Black arrows indicate the sector inoculated with the selected strain that was capable of growth on all the above medium except YNA. After repeated culturing of this strain in YPX medium for 30 cycles, it appeared to have adapted as seen from the comparison of its growth (bottom left panel) with an unadapted culture (bottom right panel). The adapted strain was then designated as strain Y161. On YNA medium, Y161 showed poor growth in the first 3 days, and no further increase in colony size or number was observed in the next 4 days.