Formate Dehydrogenase Improves the Resistance to Formic Acid and Acetic Acid Simultaneously in Saccharomyces cerevisiae

Abstract

Bioethanol from lignocellulosic biomass is a promising and sustainable strategy to meet the energy demand and to be carbon neutral. Nevertheless, the damage of lignocellulose-derived inhibitors to microorganisms is still the main bottleneck. Developing robust strains is critical for lignocellulosic ethanol production. An evolved strain with a stronger tolerance to formate and acetate was obtained after adaptive laboratory evolution (ALE) in the formate. Transcriptional analysis was conducted to reveal the possible resistance mechanisms to weak acids, and fdh coding for formate dehydrogenase was selected as the target to verify whether it was related to resistance enhancement in Saccharomyces cerevisiae F3. Engineered S. cerevisiae FA with fdh overexpression exhibited boosted tolerance to both formate and acetate, but the resistance mechanism to formate and acetate was different. When formate exists, it breaks down by formate dehydrogenase into carbon dioxide (CO2) to relieve its inhibition. When there was acetate without formate, FDH1 converted CO2 from glucose fermentation to formate and ATP and enhanced cell viability. Together, fdh overexpression alone can improve the tolerance to both formate and acetate with a higher cell viability and ATP, which provides a novel strategy for robustness strain construction to produce lignocellulosic ethanol.

Saccharomyces cerevisiae strains performing similarly during fermentation of lignocellulosic hydrolysates show pronounced differences in transcriptional stress responses

“…Adaptive laboratory evolution to improve formate tolerance in S. cerevisiae CEN.PK 113-5D led to a ~ 3,000-fold higher expression of the formate dehydrogenase-encoding genes FDH1 , YPL276W , and FDH2 ( 49 ). Overexpression of FDH1 has been demonstrated to increase tolerance to formic acid and acetic acid, through decomposition of formic acid and generation of additional ATP, respectively ( 50 ).…”

Renewing Lost Genetic Variability with a Classical Yeast Genetics Approach

“…Overall, the sporulation of YI30 resulted in MSCs with differential ability to withstand increasing concentrations of formic acid and was useful for the selection of a few candidates with promising phenotypes to be further studied to both shed light on the still poorly investigated mechanism of formic acid tolerance in S. cerevisiae and to develop superior yeast strains with increased resistance to this weak acid [ 57 , 58 ]. Few MSCs, indeed, showed a lower lag phase, thus reacting much faster than the parental strains thanks to strong and strain-specific intracellular metabolomic reactions.…”

Fixing carbon dioxide in situ during ethanol production by formate dehydrogenase

“…This makes ScFDH1 overexpression play a bigger role in the fermentation of lignocellulosic hydrolysates. 24 NADH plays a vital role in CO 2 fixation by FDHs. Desirably, during the production of ethanol, TCA and biomass growth from glucose generate surplus NADH.…”

“…22,23 Consequently, the co-production of bioethanol and valueadded formate from CO 2 can significantly decrease production costs. In our previous study, 24 ScFDH1 was overexpressed in the main bioethanol producer Saccharomyces cerevisiae. It was reported that overexpressed ScFDH1 improved the tolerance to formic acid and acetic acid simultaneously derived from lignocellulosic hydrolysate by increasing the cell viability.…”