Random methods such as mutagenesis, adaptation, hybridization, and evo­lutionary engineering [130] have been employed to obtain improved xylose­utilizing [5,42,110,131] (strains TMB3400, C1, C5, BH42, RWB218, RWB202- AFX, H2490-4, Tables 1, 3, and 4) and arabinose-utilizing [71] S. cerevisiae strains. Some of the resultant strains have been analyzed in order to identify molecular traits related to the improved ethanolic fermentation of pentose sugars. High-throughput technologies, such as transcription analysis [71,91, 109,132], enzyme and metabolite analysis [110], and proteome analysis [57], have been used. In many cases, the mutations and alterations observed in mutant strains are the same as have been earlier rationally engineered, con­firming previous knowledge and hypotheses about control and regulation of pentose metabolism. So far, no report exists where completely novel infor­mation would have been obtained from high-throughput molecular analyses. Thus, the investigations have mainly served to confirm and demonstrate the validity of the technologies.

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