Part:BBa_K4886004
Pfba-FXpk(BD)
It is a part that is responsible for expressing F/Xpk from Clostridium tyrobutyricum. with fba promotor. X-FXpk(BD) vector (7670 bp) was obtained by using the constructed recombinant plasmid Pthl-FXpk(BD) as template and X-PN-F and X-PN-R as primers. Using the genome of Clostridium butyricum as template, P-Ptkt-F and P-Ptkt-R as primers, Ptkt gene fragment (300bp) was amplified. Gibson assembly method was used to connect the Ptkt fragment to the X-FXpk(BD) linearized vector. Colony PCR (1396 bp) was performed on the transformed colonies with primers P-Ptkt-F and CX. The positive colonies with correct colony PCR were transferred, plasmid was extracted, and the recombinant plasmid was obtained after sequencing verification.
Sequence and Features
- 10INCOMPATIBLE WITH RFC[10]Illegal EcoRI site found at 1689
Illegal XbaI site found at 632 - 12INCOMPATIBLE WITH RFC[12]Illegal EcoRI site found at 1689
- 21INCOMPATIBLE WITH RFC[21]Illegal EcoRI site found at 1689
- 23INCOMPATIBLE WITH RFC[23]Illegal EcoRI site found at 1689
Illegal XbaI site found at 632 - 25INCOMPATIBLE WITH RFC[25]Illegal EcoRI site found at 1689
Illegal XbaI site found at 632 - 1000COMPATIBLE WITH RFC[1000]
Results
（1）Plasmid construction
By using a recombinant plasmid pMTL-Pthl-F/Xpk(BD) as a template, and X-PN-F and X-PN-R as primers, we obtained a X-F/Xpk(BD) vector (7670 bp). Pfba fragment (300bp) was amplified from the genome template of C. acetobutylicum using P-Pfba-F and P-Pfba-R as primers, by PCR. DNA electrophoresis confirmed the lengths of the PCR products (Figure 2). Pfba fragment was ligated with X-F/Xpk(BD) vector into a pMTL-Pfba-FXpk(BD) recombinant plasmid by Gibson assembly. The plasmid was transformed into a E. coli JM109 strain. After verification by colony PCR and DNA electrophoresis (623 bp), positive colonies were transferred and expanded. Gene sequencing was used to verify that the plasmid extracted from the colonies was pMTL-Pfba-FXpk(BD).
Figure 2 Verification of Pfba (300bp) by DNA gel electrophoresis
（2）Transfection and function analysis
By using E. coli CA434 as a donor strain, pMTL-Pfba-FXpk(BD) plasmid was transferred to C. tyrobutyricum, noted as Ct(Pfba F/Xpk(BD)). C. tyrobutyricum transfected with pMTL-Pthl-F/Xpk(BD) was used as the control. C. tyrobutyricum transfected with pMTL-Ptkt-F/Xpk(BD) was noted as Ct(Ptkt F/Xpk(BD)). pMTL-Pthl-F/Xpk(BD) and pMTL-Ptkt-F/Xpk(BD) plasmids were same as pMTL-Pfba-FXpk(BD) except using a different promoter, Pthl or Ptkt. Xylose was used as the carbon source for fermentation.
Fermentation experiment showed that the growth of Ct(Pfba F/Xpk(BD)) was better than that of the control and that of Ct(Ptkt F/Xpk(BD)) (Figure 3).
HPLC experiment showed that after culturing on xylose for 48h, the yield of butyric acid was 2.58 g/L in Ct(Pfba F/Xpk(BD)), higher than the 2.40 g/L yield in the control (Figure 4). Ct(Pfba F/Xpk(BD)) showed higher glucose consumption than the control. However, the yield of butyric acid was 2.02 g/L in Ct(Ptkt F/Xpk(BD)), lower than the 2.40 g/L yield in the control.
From this, it can be concluded that using Pfba as the promoter for F/Xpk(BD) gene can enhance growth and increase butyric acid production in the NOG pathway of the engineered C. tyrobutyricum, compared with Pthl and Ptkt.
Figure 3 Growth performance of Ct(Pfba F/Xpk(BD)) and Ct(Ptkt F/Xpk(BD)) （Control：Ct(F/Xpk-BD) with Pthl promoter）
Figure 4 Butyric acid yield and glucose consumption of Ct(Pfba F/Xpk(BD)) and Ct(Ptkt F/Xpk(BD))（Control：Ct(F/Xpk-BD) with Pthl promoter）
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