Expression of Aspergillus niger glucose oxidase in yeast Pichia pastoris SMD1168

The aim of this study was to establish a system for high expression of Aspergillus niger glucose oxidase (GOD) with glyceraldehyde-3-phosphate dehydrogenase gene promoter (pGAP) in Pichia SMD1168. The GOD gene from A. niger accc30161 was inserted into pGAPZ alpha A plasmid carrying a pGAP promoter and was expressed in yeast Pichia pastoris. The expression vector, pGAPZ alpha A-GOD, was validated by colony polymerase chain reaction (PCR), agarose gel electrophoresis, restriction enzyme analysis and sequencing methods. The pGAPZ alpha A-GOD vector was transformed into yeast P. pastoris SMD1168 by electroporation and the positive strain was validated by PCR. The expression and enzyme activity of the recombinant GOD were analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and enzymatic detection. The recombinant GOD in yeast was purified by ion exchange chromatography, and its biochemical properties (dynamics, thermal and pH stability) were analysed. The obtained results showed that the expression vector, pGAPZ alpha A-GOD, was successfully constructed to express A. niger accc30161 GOD protein. After transformation, the pGAPZ alpha A-GOD DNA fragment had been integrated into the P. pastoris SMD1168-GOD genome. High expression of GOD was achieved in SMD1168-GOD, and the enzyme activity of GOD reached 107.18 U/mL in the supernatant of the culture medium at 30 degrees C and pH 6. The activity of recombinant GOD protein in yeast was 1.35-fold higher than the commercial A. niger GOD, and its affinity to glucose, thermal stability and pH stability are similar to commercial GOD. Using pGAP promoter, A. niger GOD protein is efficiently expressed in recombinant P. pastoris SMD1168-GOD with defective protease.