To increase the biological activities of flavonoids and to enhance their stability and solubility by functionalization reactions (polymerization, esterification, alkylation, glycosylation and acylation), an increase in the number of hydroxyl groups in these molecules is needed. Hydroxylation reactions may be achieved using either chemical or enzymatic methods, the latter being more highly specific than the former. In our study, the flavonoid 3' hydroxylase (F3'H) from Gerbera hybrid, functionally expressed in Saccharomyces cerevisiae, was used to hydroxylate naringenin (the first flavonoid core synthesized in plants). Furthermore, we studied factors that may affect naringenin hydroxylation by recombinant cell-like yeast growth on selective or rich media and plasmid stability. The whole recombinant cells hydroxylated naringenin at position 3' to give eriodictyol. In a selective media, the yeast failed to grow to high cell densities (maximum 5 g/L), but the plasmid stability was nearly 90 %, and naringenin hydroxylation reached 100%. In a rich complex media, the biomass reached 10 g/L, but the yield of naringenin hydroxylation reached only 71 %, and the plasmid stability decreased. When yeast functionally expressing F3'H from Gerbera hybrid was used, in a selective media, 200 mg/L of eriodictyol from naringenin was produced.