(544b) Engineering Escherichia coli for Ethanol Production from Pyrolytic Sugar

Lignocellulosic biomass has been extensively utilized as a source of carbon and energy for the fermentative production of ethanol and other biorenewable fuels. However, the sugar streams released from biomass frequently contain inhibitory contaminants, such as aldehydes, phenolic compounds, and alcohols, which will inhibit the growth, biofuel production, and substrate utilization of microorganisms during fermentation. It is necessary to improve the performance of  the biocatalysts. Hybrid processing, which we applied, is a method that employs a combination of thermochemical and biochemical steps to produce biofuels and chemicals from fermentation substrates, which are derived from lignocellulosic biomass, through biocatalysts. Because it is difficult to attribute the toxicity to one component or mechanism due to the complexity and uncertainty of pyrolytic sugar, it is unable to engineer the biocatalyst rationally to increase its robustness. Therefore, metabolic evolution is sufficient to acquire a strain with the desired phenotype of increased tolerance to pyrolytic sugar. The mutations of the evolved strains responsible for the increased tolerance is to be verified. Besides, we also evaluate the toxocity of the pyrolytic sugar by inspecting its impact on the cell membrane from the aspects of membrane fluidity and leakage.