Bioconversion of ferulic acid into aroma compounds by newly isolated yeast strains of the Latin American biodiversity

Nine yeast strains isolated from Latin American biodiversity were screened for ferulic acid (FA) consumption and conversion into aroma compounds such as vanillin, vanillic acid (VA), and 4-vinylguaiacol (VG). Selected strains (Rhodotorula mucilaginosaUFMG-CM-Y3647, UFMG-CM-Y2190, UFMG-CM-Y665) were evaluated in flask experiments to investigate the influence of the pH media on bioconversion and a two-step process was conducted to maximize the metabolites production. The effect of pH was found to be significantly important for FA bioconversion, as acidic conditions (pH < 6.0) improved VA accumulation, with highest production of 1.14 +/- 0.02 and 1.25 +/- 0.03 g/L shown by UFMG-CM-Y3647 and UFMG-CM-Y2190, respectively. The two-step process favored 4-VG production for most strains, being UFMG-CM-Y2190 the best producer, its cultures reaching 1.63 +/- 0.09 g/L after 55 hr, showing a productivity of 29.59 +/- 1.55 mg/(L center dot hr), as glucose affected the metabolites pool and redirected yeast metabolism.R mucilaginosaUFMG-CM-Y3647 was selected for scaled-up cultivations in a 2-L bioreactor, where pH-controlled pH 5.5 and aeration of 2.5 vvm was found to be the best condition to improve VA productivity, attaining final concentrations of 1.20 +/- 0.02 g/L-1(78% molar yield) and a productivity of 40.82 +/- 0.57 mg/(L center dot hr).

Automated summary

Nine yeast strains isolated from Latin American biodiversity were evaluated for ferulic acid (FA) utilization and conversion into aroma compounds. The influence of pH on bioconversion was found significant, with acidic conditions enhancing vanillic acid (VA) accumulation. A two-step process favored 4-vinylguaiacol (VG) production, with strains showing varied productivity under different pH levels. Yeast strain R. mucilaginosa UFMG-CM-Y3647 was selected for scaled-up cultivations, achieving improved VA productivity under controlled pH and aeration conditions.