(425f) Transcriptomic and Proteomic Profiling of Ethanol-Tolerant Clostridium Thermocellum

Clostridium thermocellum is a cellulolytic and ethanogenic organism that could convert cellulosic materials directly to bioethanol. However, its low ethanol tolerance has been an obstacle for the process industrialization. A strain tolerant of 6% (w/v) ethanol obtained by sequential transfer was capable of producing twice higher concentration of ethanol than wild type in fed-batch culture. Transcriptomic and proteomic analysis were performed on exponentially growing and stationary phase wild type and tolerant strain. Wild type and tolerant strain exhibited similar dynamics in transiting from growth to stationary phase in many gene classes including molecular chaperones, cellulosome, and ATP synthases. Whereas many genes underwent different responses between them, and these genes were involved in membrane transport of cellodextrin, oligopeptide, nitrogen and sulfate, maintaining redox homeostasis, such as ferredoxin, thioredoxin and rubredoxin, and hydrogen production. Combining transcriptomic data and iTRAQ-based quantitative proteomic results, genes and gene classes related to high ethanol tolerance feature were explored, which has shed light on the mechanism of ethanol tolerance of Clostridium thermocellum.