Multilevel Defense System (MDS) Relieves Multiple Stresses for Economically Boosting Ethanol Production of Industrial Saccharomyces cerevisiae

In the biofuel industry, improving the tolerance of Saccharomyces cerevisiae to the multiple stresses is essential to enhance the production efficiency and reduce the economic cost. We herein developed a multilevel defense system (MDS) by random assembly of tolerance genetic circuits, adaptive evolution, and multistep screening to obtain industrial yeasts with higher robustness and productivity. MDS was applied to increase the ethanol concentration by 6.9% in industrial pilot-scale fermentation at high temperature, and the energy consumption for the cooling was decreased by 45.1% compared with that for the normal process. Furthermore, MDS showed a significant effect on relieving the multiple stresses by reducing intracellular reactive oxygen species (ROS) and balancing the productive transcriptional performance. This system offers a new solution for remolding industrial yeast and may accelerate further development of ethanol refinery.