Engineering Clostridium ljungdahlii as the gas-fermenting cell factory for the production of biofuels and biochemicals

Functional dissection and modulation of the BirA protein for improved autotrophic growth of gas‐fermenting Clostridium ljungdahlii

“…In view of that biotin synthesis is a high energy‐consuming process in cells (Feng et al ., 2013), such a BirA‐mediated feedback regulation on biotin synthesis may be crucial for the control of energy expenditure in bacteria. Theoretically, this regulatory mechanism is especially important for gas‐fermenting clostridia because the carbon fixation and assimilation in these autotrophic bacteria are a net energy consumption process (Zhang et al., 2020a,2020b), and excessive energy consumption in biotin synthesis will cause metabolic burden. But interestingly, a modified Cl BirA with only enzymatically active domain led to a better performance of C. ljungdahlii in gas fermentation (Figs 6 and 8), indicating that an uncontrolled overproduction of biotin is not the key point for the autotrophic growth of C. ljungdahlii .…”

“…However, to date, this aspect remains minimally explored due to the challenges in genetic tools. Specific to transcriptional regulators (TFs), to our knowledge, only a global regulator CcpA and a TetR‐family regulator (CAETHG_0459) have been identified and characterized in these autotrophic bacteria (Lemgruber et al ., 2019; Zhang et al., 2020a,2020b). CcpA was found to directly regulate the expression of some WLP genes in Clostridium.…”

“…CcpA was found to directly regulate the expression of some WLP genes in Clostridium. ljungdahlii , and the elimination of CcpA’s inhibition on these genes could significantly enhance CO 2 utilization (Zhang et al., 2020a,2020b). CAETHG_0459, as a transcription activator in Clostridium autoethanogenum , can directly bind to the core enzyme of RNA polymerase and subsequently activate the expression of multiple WLP genes (Lemgruber et al ., 2019).…”

Protein acetylation-mediated cross regulation of acetic acid and ethanol synthesis in the gas-fermenting Clostridium ljungdahlii

“…Our current knowledge includes an understanding of the metabolic pathways responsible for the formation of acids and alcohols as well as of the conversion of acids to alcohols in autotrophic acetogens ( 1 , 4 , 5 , 6 , 7 ). Furthermore, some key enzymes and the corresponding genes have been identified and characterized ( 5 ).…”

A Heterodimeric Reduced-Ferredoxin-Dependent Methylenetetrahydrofolate Reductase from Syngas-Fermenting Clostridium ljungdahlii

“…This process can not only capture CO 2 to reduce its emission but also make wastes recyclable through directly fermenting the waste gases from steel factories or those from waste gasification. The use of acetogens in the process has attracted considerable attention as the basis for a new and valuable biomanufacturing platform ( 4 ).…”