Abstract
Recent studies indicated that overexpression of dxs and idi genes in bacteria transformed with crtEBI genes dramatically improved the production of lycopene. The aim of the present study was the assessment of crtEBI-transformed S. cerevisiae overexpressing the bacterial synthetic dxs and yeast idi genes for lycopene production. The two genes were driven by galactose-induced promoters namely GAL1 and GAL10, respectively, of the pESC-LEU yeast vector of which gene cassettes were inserted in pTEF1/Zeo vector. The synthetic dxs gene was constructed in accordance with the preferred codon usage in S. cerevisiae with no change in the resulting amino acid sequences. The RT-PCR analysis indicated that the two genes were efficiently transcribed in crtEBI-transformed S. cerevisiae cells. The highest production of lycopene (6755 mu g lycopene/g dry cell weight) was reached for yeast cells transformed with the two genes, which is higher than the previously reported lycopene levels in yeast. The level of Acetyl Coenzyme A (Acetyl-CoA) was negatively related to that of lycopene in transformed S. cerevisiae cells, suggesting that lycopene and Acetyl-CoA biosyntheses compete for the use of pyruvate.