Part:BBa_K2739009
Hybrid promoter-PhaCAB-Bktb
This is a composite part that was created to allow us to test the functionality of BktB. PHA operon is known to produce bioplastic PHB. The coexpression of the BktB allow the production of copolymer, PHBV.
Usage and Biology
The BktB was isolated from R. eutropha H16 and being recognised as a phaA paralogous, which allows the formation of 3-ketovaleryl-CoA and leads to PHBV production. In order to enhance the 3HV fraction in PHBV, paralog bktB was introduced into E. coli BL21 (DE3) with co-expression of phaCAB operon from Ralstonia eutropha.
Figure 1. Schematic illustration of the pathways leading to the PHBV biosynthesis.
Results and Discussion
E. coli strain BL21 (DE3) that harboured these two plasmids was spread on the Nile red agar plates with negative control (pSB1C3) respectively, and two plates were exposed to blue light. Compared with negative control, the strong Nile red fluorescence from strains that harboured either pSB1C3-phaCAB-bktB or pSB1C3-phaCB-bktB, indicating that PHA (PHB and PHBV) production was assessed after 24 hours.
Figure 2. Nile red agar plate detection of PHA production.
Paralogous gene bktB represented similar function with phaA gene in the pathway, which showed higher specificity to C5 monomers contributed to the PHBV productivity and 3HV fraction. Although gas chromatograph remained to be done to analyse PHBV composition, lower melting temperature still gave strong suggestion that replace phaA gene with bktB could significantly increase the PHBV content in PHA production and co-expression of two genes would show small increase of PHBV production. Combined with the culture condition optimisation, cells harbouring pSB1C3-phaCB-bktB showed great potential to improve production of PHBV with higher 3HV fraction.
Tm 1(℃.) Tm 2 (℃.) Tm 3 (℃.) Pure PHB product from sigma 170-179 168-176 168-174 PHBV with 12% 3HV from Sigma 159-161 160-160 161-164 PHA from pSB1C3-phaCAB 160-168 160-162 161-163 PHA from pSB1C3-phaCB-bktB 150-155 149-151 149-152 PHA from pSB1C3-phaCAB-bktB 155-159 156-161 157-159 PHB extraction 168-180 166-178 169-179 Table 1. Melting Temperature Measurement
Future work
Gas chromatograph analysis remain to be done to give more specific information about the composition of extracted PHA products including the percentage of PHBV content and the fraction of 3HV in PHBV, which are essential for confirming the effect of bktB on PHBV production.
References
Yu, S.T., Lin, C.C. and Too, J.R., 2005. PHBV production by Ralstonia eutropha in a continuous stirred tank reactor. Process Biochemistry, 40(8), pp.2729-2734. Shojaosadati, S.A., Varedi Kolaei, S.M. and Babaeipour, V. 2008. Recent advances in high cell density cultivation for production of recombinant protein. Iranian Journal of Biotechnology, 6(2), pp.63-84. Mifune, J., Nakamura, S. and Fukui, T., 2010. Engineering of pha operon on Cupriavidus necator chromosome for efficient biosynthesis of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) from vegetable oil. Polymer Degradation and Stability, 95(8), pp.1305-1312.
Sequence and Features
- 10COMPATIBLE WITH RFC[10]
- 12INCOMPATIBLE WITH RFC[12]Illegal NheI site found at 7
Illegal NheI site found at 30 - 21INCOMPATIBLE WITH RFC[21]Illegal BglII site found at 979
Illegal BglII site found at 1804 - 23COMPATIBLE WITH RFC[23]
- 25INCOMPATIBLE WITH RFC[25]Illegal NgoMIV site found at 285
Illegal NgoMIV site found at 356
Illegal NgoMIV site found at 956
Illegal NgoMIV site found at 1268
Illegal NgoMIV site found at 1547
Illegal NgoMIV site found at 2199
Illegal NgoMIV site found at 2221 - 1000INCOMPATIBLE WITH RFC[1000]Illegal BsaI site found at 4065
Illegal BsaI site found at 5108
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