Part:BBa_K1972013
dszBAC with tac promoter and dszD with lac promoter
We constructed dszBCA genes with tac promoter and dszD gene with lac promoter choose E.coli BL21 as our host cell. When IPTG is added to our system, DszABCD enzymes will be successful expressed and these four enzymes convert dibenzothiophene (DBT) undergoes through three successive oxidation steps and one a hydrolytic step to 2-hydroxybiphenyl (2HBP) by the 4s pathway.
Each single enzyme gene was synthesized by Generay with E.coli optimized and we constructed them together and suquencing comformed. the sequences can be found in NCBI (GenBank Accession number L37363.1)
Sequence and Features
- 10COMPATIBLE WITH RFC[10]
- 12COMPATIBLE WITH RFC[12]
- 21INCOMPATIBLE WITH RFC[21]Illegal BglII site found at 2737
Illegal XhoI site found at 4243 - 23COMPATIBLE WITH RFC[23]
- 25INCOMPATIBLE WITH RFC[25]Illegal NgoMIV site found at 267
Illegal NgoMIV site found at 1761
Illegal AgeI site found at 1104
Illegal AgeI site found at 1865
Illegal AgeI site found at 2148
Illegal AgeI site found at 2966
Illegal AgeI site found at 4431 - 1000INCOMPATIBLE WITH RFC[1000]Illegal BsaI.rc site found at 864
The DszB desulfurase catalyzes the rate-limiting step of the 4S-pathway and the Y63F amino acid substitution was previously reported to enhance its activity and stability. Therefore, the Y63F amino acid substitution of the DszB desulfurase was performed.
Figure 1. Bio-circuit of BBa_K1972013 after our third optimization
Furthermore, the desulfurization experiment showed that the activities of enzyme C and A were still stronger than B, which caused undesirable accumulation of intermediate products (DBTO2/HBPS), seriously affecting the activity of enzyme B. The promoters of dsz genes were further adjusted. Gene dszB, dszC and dszA were controlled by the tac promoter, which was strong enough and endogenous for E.coli. At the same time, dszD was under the weak lac promoter as an independent operon, making the expression of enzyme D relatively weak, with the purpose of indirectly attenuating the effect of the enzyme A and C (as shown in Figure 1).
Figure 2. The desulfurization results of Recombinant strain BL21-dszBACD (optimized) tested by HPLC
The desulfurization efficiency of the recombinant strain BL21-dszBACD (optimized) is greatly improved.
Reference
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[2] Franchi E RF, Serbolisca L, et al. Vector development, isolation of new promoters and enhancement of the catalytic activity of the Dsz enzyme complex in Rhodococcus sp. strains[J]. Oil & gas science and technology, 2003, 58(4): 515-520.
[3] Abin-Fuentes A, Mohamed Mel S, Wang DI, Prather KL. Exploring the mechanism of biocatalyst inhibition in microbial desulfurization[J].Applied and environmental microbiology.2013,79(24):7807-17.
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[6] Li GQ, Li SS, Zhang ML, Wang J, Zhu L, Liang FL, et al. Genetic rearrangement strategy for optimizing the dibenzothiophene biodesulfurization pathway in Rhodococcus erythropolis[J].Applied and environmental microbiology.2008,74(4):971-6.
[7] Hirasawa K, Ishii Y, Kobayashi M, Koizumi K, Maruhashi K. Improvememt of Desulfurization Activity in Rhodococcus erythropolis KA2-5-1 by Genetic Engineering[J].Bioscience, Biotechnology and Biochemistry.2014,65(2):239-46.
[8]Martínez I, Mohamed M E S, Rozas D, et al. Engineering synthetic bacterial consortia for enhanced desulfurization and revalorization of oil sulfur compounds[J]. Metabolic engineering, 2016, 35: 46-54.
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