Gene Circuit Boosts High-Temperature Fermentation with Low Energy Consumption

The growth and production of microorganisms in bioconversion are often hampered by heat stress and product feed-back repression. In this study, the intelligent microbial heat regulating engines (IMHeRE) which are novel gene circuits were developed and customised to improve the thermo-robustness of Escherichia coli and Saccharomyces cerevisiae via the integration of a thermotolerant system and a quorum regulating system. At the cell level, the thermotolerant system composed of different heat shock proteins and RNA thermometers hierarchically expands the optimum temperature by sensing heat changes in both strains. At the community level, the quorum regulating system dynamically programs the altruistic sacrifice of individuals to reduce metabolic heat release by sensing the temperature and cell density in Escherichia coli. Using this hierarchical, dynamical and multilevel regulation, the IMHeRE are able to significantly improve cell growth and production. In real applications, the production of lysine was increased five-fold at 40°C using the IMHeRE. Additionally, both tolerant to thermo stress and high concentration of ethanol in Saccharomyces cerevisiae has recently become much useful as the industry moves toward the use of simultaneous sacchrification and fermentation (SSF). So double-tolerance gene circuits were rationally designed and successfully obtained through one-pot parts random assembly via Golden Gate Shuffling. The cooling water and energy consumption are all significantly reduced of 31% and 24% as well as ethanol production and productivity enhanced by 5% and 12% by engineered Saccharomyces cerevisiae, respectively, in 35-37°C fermentation. Our work provides new potential for the development of bioconversion by conserving energy and increasing productivity. 

Keywords: gene circuit, hierarchical thermotolerance, ethanol tolerance, bioconversion, microorganism, synthetic biology