Enhanced tolerance of Clostridium tyrobutyricum to furan derivatives for efficient butyric acid production by overexpressing native transporter genes

Furan aldehydes generated during the hydrolysis of lignocellulosic biomass are toxic to Clostridium tyrobutyricum, severely inhibiting its butyric acid production. This study confirmed that overexpression of the ABC-transporter gene CtAT2 in C. tyrobutyricum significantly increased furfural tolerance (> 3.0 g/L) and butyrate production (13.8 %). Conversely, overexpression of the MFS-transporter gene CtMT1 enhanced tolerance to HMF (> 4.0 g/ L). However, co-expression of CtAT2 and CtMT1 in C. tyrobutyricum failed to improve the strain's tolerance to furfural and HMF. Using undetoxified corncob acid hydrolysate as the carbon source, the recombinant strain ATCC 25755/AT2 exhibited excellent performance in butyric acid fermentation due to its heightened furfural tolerance and improved butyrate production. ATCC 25755/AT2 demonstrated impressive butyrate production and productivity in fed-batch fermentation, reaching 29.8 g/L and 0.23 g/L & sdot;h, respectively. These values rep-resented a 22.6 % increase in butyrate production and a 27.8 % increase in productivity compared to the wild-type strain.