Efficient chemoselective biohydrogenation of 1,3-diaryl-2-propen-1-ones catalyzed by Saccharomyces cerevisiae yeasts in biphasic system

A series of chalcones (1–9) was synthesized by base catalyzed aldol condensation with 50–94% yields. These α,β-unsaturated carbonyl compounds were used as substrates in biotransformation reactions mediated by three industrial Saccharomyces cerevisiae strains in biphasic systems. Several reaction parameters were evaluated, such as yeast concentration, temperature, pH, substrate concentration, organic solvent, volume of aqueous and organic phases and the influence of substituent groups on chalcones 1–9. The biotransformation was chemoselective and formed only the corresponding saturated ketones. The highest conversion (>99%) to the dihydrochalcone was obtained at 30–45 °C and pH above 5.5, while the cellular and substrate concentrations also showed a strong influence on the biohydrogenation reaction. Organic solvents with log P >3.2 (hexane or heptane) were the most appropriate, and 40–80% of aqueous phase allowed the highest conversions probably by maintaining the yeast enzymes catalytically active. The influence of substituents on rings A and B of chalcones 1–9 was low and no correlation between the donor or withdrawing electron groups was observed.