Journals / Turkish Journal of Biology / 2015 / Cilt: 39 - Sayı: 2
Enhancing the expression of Aspergillus niger Ã-mannanase in Pichia pastoris by coexpression of protein disulfide isomerase
- Journal
- Turkish Journal of Biology
- Pages
- 312–319
- DOI
- —
Abstract
A gene encoding Ã-mannanase from Aspergillus niger GIM3.452 was amplified and inserted into a pPIC9K vector. The resulting recombinant plasmid, pPIC9K-MAN, was transformed into Pichia pastoris GS115. One strain (GSKM-1) having the highest Ã-mannanase activity of 26.6 U/mL was obtained. In order to increase the secretion of Ã-mannanase in P. pastoris, we constructed a double recombinant yeast and made it coexpress protein disulfide isomerase. One strain (GSKZ\alphaM2) with the highest Ã-mannanase activity of 40 U/mL was then obtained and used to optimize expression conditions. When the GSKZ\alphaM2 strain was induced under the optimized conditions (methanol concentration 1.5%, induction time 7 days), Ã-mannanase activity reached 222.8 U/mL. SDS-PAGE and deglycosylation assays demonstrated that the recombinant A. niger Ã-mannanase, a glycosylated protein with an apparent molecular weight of 45 kDa, was secreted into the culture medium. It displayed maximum activity at pH 4.4 and 60 °C, and it was stable in a pH range of 2.4-8.0 and at a temperature of 60 °C or below. Our results suggested that coexpression chaperones could improve the yield of Ã-mannanase.
Özet
A gene encoding Ã-mannanase from Aspergillus niger GIM3.452 was amplified and inserted into a pPIC9K vector. The resulting recombinant plasmid, pPIC9K-MAN, was transformed into Pichia pastoris GS115. One strain (GSKM-1) having the highest Ã-mannanase activity of 26.6 U/mL was obtained. In order to increase the secretion of Ã-mannanase in P. pastoris, we constructed a double recombinant yeast and made it coexpress protein disulfide isomerase. One strain (GSKZ\alphaM2) with the highest Ã-mannanase activity of 40 U/mL was then obtained and used to optimize expression conditions. When the GSKZ\alphaM2 strain was induced under the optimized conditions (methanol concentration 1.5%, induction time 7 days), Ã-mannanase activity reached 222.8 U/mL. SDS-PAGE and deglycosylation assays demonstrated that the recombinant A. niger Ã-mannanase, a glycosylated protein with an apparent molecular weight of 45 kDa, was secreted into the culture medium. It displayed maximum activity at pH 4.4 and 60 °C, and it was stable in a pH range of 2.4-8.0 and at a temperature of 60 °C or below. Our results suggested that coexpression chaperones could improve the yield of Ã-mannanase.