Improved growth and ethanol fermentation of Saccharomyces cerevisiae in the presence of acetic acid by overexpression of SET5 and PPR1

Abstract

To better understand the contribution of zinc-finger proteins to environmental stress tolerance, particularly inhibition from acetic acid, which is a potent inhibitor for cellulosic ethanol production by microbial fermentations, SET5 and PPR1 were overexpressed in Saccharomyces cerevisiae BY4741. With 5 g/L acetic acid addition, engineered strains BY4741/SET5 and BY4741/PPR1 showed improved growth and enhanced ethanol fermentation performance compared to that with the control strain. Similar results were also observed in ethanol production using corn stover hydrolysate. Further studies indicated that SET5 and PPR1 overexpression in S. cerevisiae significantly improved activities of antioxidant enzymes and ATP generation in the presence of acetic acid, and consequently decreased intracellular accumulation of reactive oxygen species (50.9 and 45.7%, respectively). These results revealed the novel functions of SET5 and PPR1 for the improvement of yeast acetic acid tolerance, and also implicated the involvement of these proteins in oxidative stress defense and energy metabolism in S. cerevisiae. This work also demonstrated that overexpression of SET5 and PPR1 would be a feasible strategy to increase cellulosic ethanol production efficiency.

Enhanced fermentative performance under stresses of multiple lignocellulose-derived inhibitors by overexpression of a typical 2-Cys peroxiredoxin from Kluyveromyces marxianus

“…6b). Above all, our results and some previous reports all confirmed that oxidoreductases maintained a normal level of oxidoreductases, which eventually manifested as an apparently enhanced tolerance of S. cerevisiae to multiple lignocellulose-derived inhibitors [9, 29, 34]. …”

“…Therefore, oxidoreductases help remove the excess ROS, maintaining it at a normal level, to achieve an elevated tolerance and reduce damages to cells. Intracellular ROS in cells with an increased tolerance has been reported to decrease under inhibitors, no matter what strategies were adopted [9, 29, 34]. …”

Towards efficient bioethanol production from agricultural and forestry residues: Exploration of unique natural microorganisms in combination with advanced strain engineering

“…The results indicated that specific ethanol productivity was improved by nearly four and three times independently in the presence of 2 g/L acetic acid and 1.5 g/L furfural (Chen et al, 2016). Similarly, SET5 and PPR1 were captured in our transcriptomic research by comparing zinc addition with the non-addition control, and it was demonstrated that with these two genes overexpression approximately 10% increased ethanol production was obtained in the fermentation from corn stover hydrolysate (Zhang et al, 2015).…”

The Genetic Requirements for Pentose Fermentation in Budding Yeast

“…Temporal analysis of ethanol production and sugar depletion revealed that wild-type cells grown on 2% glucose consumed the sugar within 24 hr, producing 7 g/L of ethanol (Figure 1B and Figure S1 in File S1), which corresponds to ∼70% of the theoretical yield (Zhang et al 2015). Growth on galactose produced a similar amount of ethanol but at a slower rate, depleting the sugar only after ∼40 hr of growth.…”