Copy-number variation of xylose isomerase for efficient adaptive evolution of engineered industrial Saccharomyces cerevisiae strain

The development of yeast strains capable of fermenting a five-carbon sugar xylose is a key step for achieving a feasible production of second-generation ethanol. An efficient expression of xylose isomerase (xylA), the primary gene of xylose metabolism, is essential in order to achieve an efficient conversion of this sugar. To enhance strain performance following initial genetic engineering steps, cycles of adaptive evolution are typically conducted in xylose medium. However, this process can be slow as it depends on xylA activity. In this study, we established a faster and powerful process for evolution based on the increased copy-number of xylA. The cell that presents higher copy-number of this gene during adaptive evolution in xylose media could convert this sugar and produce ethanol faster, being positively selected by evolution.