A heat-resistant xylanase xynb with high enzyme activity at low temperature and its mutant gene, application and gene sequence preparation method
A xylanase and mutant technology, applied in the fields of protein engineering and genetic engineering, can solve the problems of increased production cost, unfavorable product quality, impact, etc., and achieve the effect of less enzyme inactivation and high enzyme activity
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Embodiment 1
[0035] Embodiment 1: Obtaining of XYNB gene sequence of xylanase mutant strain
[0036] According to sequence comparison, the amino acid sequence of xylanase 1VBR from Thermotoga maritima MSB8 published in PDB and the predicted xylanase (EHA58720.1 ) have an amino acid sequence similarity of 100%. The predicted xylanase gene sequence is a gene sequence (873,589→874,572 bp) in the genome sequence of Thermotoga maritima MSB8.
[0037] Based on the codon usage preference of Pichia pastoris, the rare codons were converted to high-frequency expression codons, and the predicted xylanase (EHA58720.1) gene sequence was compared with the amino acid sequence of xylanase 1VBR Codon optimization was performed to obtain the optimized xylanase 1 VBR gene sequence (NCBI gene number: KR078269). Using the pET-22b(+)-1VBR plasmid as a template, use Taq enzyme and set the concentrations of Mg2+ and Mn2+ in the PCR system to 2.5mM and 0.8mM respectively, and the primer sequences are 5'-CGCCATGG...
Embodiment 2
[0038] Example 2: Construction of recombinant expression plasmid pPIC9K-XYNB containing xylanase mutant strain XYNB gene
[0039] Add the preferred terminator sequence of Pichia pastoris at the 3' end of the xylanase XYNB gene, and introduce restriction endonuclease EcoR I and Not I sites at the 5' end and 3' end respectively, and cross the gene sequence with Wuhan Qingke Innovation Biotechnology Co., Ltd. completed the whole gene synthesis. The optimized xylanase XYNB gene and the secreted expression vector pPIC9K were double-digested with restriction endonucleases EcoR I and Not I, and then connected with ligase to construct the recombinant expression plasmid pPIC9K-XYNB. The recombinant expression plasmid was transformed into Escherichia coli DH5α competent cells, and the positive clone strain pPIC9K-XYNB-DH5α was screened out by PCR verification method.
Embodiment 3
[0040] Example 3: Construction of Pichia pastoris genetically engineered strains that efficiently secrete and express xylanase XYNB
[0041] The LB liquid medium was used to activate the cultured strain pPIC9K-XYNB-DH5α, and the recombinant plasmid pPIC9K-XYNB was extracted. The recombinant plasmid was linearized with restriction endonuclease Bgl II, and the digested product was recovered. Refer to EasySelectTM PichiaExpression Kit to prepare Pichia GS115 competent cells. Take about 10 μg of linearized plasmid and 80 μL of competent cells, mix gently, place on ice for 15 min, transfer to a pre-cooled 0.2 cm electroporation cuvette, add 1 mL of pre-cooled 1 mol / L sorbitol immediately after the 1500V electric shock, and Let it stand in a 30°C incubator for 1 hour, spread it on an MD plate, and incubate it upside down at 30°C for about 48 hours until transformants appear.
[0042] Pick a single colony and inoculate them on MD plates containing 0.25, 0.5, 1.0, 2.0, 3.0 and 4.0 m...
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