LAUSR

A heterologous xylose utilization pathway, either xylose reductase–xylitol dehydrogenase (XR–XDH) or xylose isomerase (XI), is usually introduced into Saccharomyces cerevisiae to construct a xylose-fermenting strain for lignocellulosic ethanol production. To investigate the molecular basis underlying the effect of different xylose utilization pathways on the xylose metabolism and ethanol fermentation, transcriptomes of flocculating industrial strains with the same genetic background harboring different xylose utilization pathways were studied. A different source of xylA did not obviously affect the change of the strains transcriptome, but compared with the XR–XDH strain, several key genes in the central carbon pathway were downregulated in the XI strains, suggesting a lower carbon flow to ethanol. The carbon starvation caused by lower xylose metabolism in XI strains further influenced the stress response and cell metabolism of amino acid, nucleobase, and vitamin. Besides, the downregulated genes mostly included those involved in mitotic cell cycle and the cell division–related process. Moreover, the transcriptomes analysis indicated that the after integrate xylA in the δ region, the DNA and chromosome stability and cell wall integrity of the strains were affected to some extent. The aim of this was to provide some reference for constructing efficient xylose-fermenting strains.