Engineering Saccharomyces cerevisiae for the one-step production of a functional sweetening mixture towards food applications

Fructooligosaccharides (FOS) are recognized prebiotics with proven beneficial effects, usually produced by two-step processes. In this work, an in vivo bioprocess was developed for the one-step production of a functional sweetening mixture containing FOS. Sucrose was directly fermented by yeast towards process simplification and cost reduction. Saccharomyces cerevisiae YIL162W lacking the gene responsible for sucrose hydrolysis (SUC2) was transformed to express β-fructofuranosidase FTase inv gene from Schwanniomyces occidentalis (clone GAL1_S196), and its mutated version (clone GAL1_L196), under the inducible galactokinase (GAL1) promotor. The FTase inv mutated gene was also expressed under the glyceraldehyde-3-phosphate dehydrogenase (GPD) constitutive promoter (clone GPD_L196). GPD_L196 clone showed the highest potential for FOS production, achieving a maximum productivity of 8.9 ± 0.4 mg.g−1.h−1 after 60 h, with sucrose supplementation by two pulses, 150 g.L−1 at 0 and 24 h. When co-cultured with S. cerevisiae wild type (WT), GPD_L196 clone achieved the maximum productivity of 10.9 ± 0.5 mg.g−1.h−1 (48 h) with an 1:200 inoculum ratio (WT:GPD_L196) and 150 g.L−1 of sucrose added at 0 and 24 h. After partial purification, a sweetening mixture composed by 75 ± 2 % of FOS and 24 ± 2 % of sucrose was obtained. This bioprocess approach presents high potential for industrial production of functional sweetening mixtures towards food applications.