Modifying Yeast Tolerance to Inhibitory Conditions of Ethanol Production Processes

Abstract

Saccharomyces cerevisiae strains having a broad range of substrate utilization, rapid substrate consumption, and conversion to ethanol, as well as good tolerance to inhibitory conditions are ideal for cost-competitive ethanol production from lignocellulose. A major drawback to directly design S. cerevisiae tolerance to inhibitory conditions of lignocellulosic ethanol production processes is the lack of knowledge about basic aspects of its cellular signaling network in response to stress. Here, we highlight the inhibitory conditions found in ethanol production processes, the targeted cellular functions, the key contributions of integrated -omics analysis to reveal cellular stress responses according to these inhibitors, and current status on design-based engineering of tolerant and efficient S. cerevisiae strains for ethanol production from lignocellulose.

Keywords: cellular stress response; design-based engineering; ethanol production process; inhibitory environment; integrated -omics analysis; stress tolerance; yeast.

Figure 1

Basic unit operations for the production of ethanol by S. cerevisiae using lignocellulosic biomass hydrolyzates. Inhibitory conditions appear in pretreatment and saccharification/fermentation steps.

Figure 2

Summarized molecular responses of S. cerevisiae upon exposition to chemical and physical stresses discussed in the main text. This figure condenses the complexity of yeast stress responses upon exposition to high temperature, elevated osmolarity, and low pH. Most of these responses are also triggered upon exposition to toxic chemicals referred to in the main text. The signaling networks from membrane sensors to transcription factors which end with the reconfiguration of transcriptional programs according to stress, and the cross-talk between cellular stress responses are also depicted.