[Fermentation and purification of recombinant alpha-galactosidase from Pichia pastoris].
In order to obtain an adequate supply of alpha-galactosidase for research and practical use, the fermentation, purification and identification of the recombinant coffee bean a-galactosidase were carried out. Baffled flasks containing 100mL BMGY were inoculated with the pPIC9K-Gal/GS115 strain and allowed to grow at 30 degrees C, 250- 300r/min until a maximum optical density at 600nm (OD600) between 2.0 to 6.0 was attained. Entire 400 mL seed culture was transferred aseptically to the 5-liter fermenter, which contained 4 liter sterilized basal salts medium and 4% glycerol. The batch culture grew at 30 degrees C, pH 5.0 until the glycerol was completely consumed, and a glycerol feed was initiated to increase the cell biomass prior to induction with methanol. The culture was centrifuged at 8000 x g and the supernatant was collected. Following ultrafiltration, the retentate was balanced in 20 mmol/L sodium formicate buffer, pH 3.8 and loaded onto a cation-exchange column, HiTrap SP. The column was washed with the same buffer and bound proteins were eluted with 1 mol/L NaCl. The fractions containing recombinant a-galactosidase were pooled and concentrated with PEG20 000. Subsequently, the biochemical properties of the enzyme were determined with typical methods. At last, the fresh human blood A and B erythrocytes were incubated with the purified alpha-galactosidase at 26 degrees C for 2 4 hours. Hemagglutinins were assayed by the standard method. After an elapsed fermentation times (EFT) of 18h, the fed-batch phase was initiated to increase the cell biomass. A cellular yield of nearly 200 g/liter wet cells was achieved when induction was initiated. 72h later, the alpha-galactosidase activity against artificial substrate PNPG (PNP-alpha-galactopyranoside) achieved 36 000u per liter culture. The crude fementation supernatant contained few impurities as detected by SDS-PAGE. The supernatant was purified by cation-exchange chromatography, the target alpha-galactosidase was eluted with 40% 1mol/L NaCl and showed a 41kD band on SDS-PAGE. After concentration, the final recovery was about 41%. The Michaelis constant of the recombinant alpha-galactosidase was determined as 0.275 mmol/L, which slightly lower than the nature enzyme and suggested a higher affinity with specific substrate. When human blood type B erythrocytes pretreated with 100u/mL recombinant alpha-galactosidase reacted with bood type B antiserum, no hemagglutination occurred. This suggested that the B antigens had been removed by the enzyme successfully. These results demonstrated that the recombinant alpha-galactosidase could be produced in largescale and made it possible to explore the application of alpha-galactosidase in more fields.
Gao
Xin
X
Beijing Institute of Transfusion Medicine, Beijing 100850, China. gaox@nic.bmi.ac.cn
Yang
Jun
J
Li
Su-Bo
SB
Liu
Ze-Peng
ZP
Zhang
Yang-Pei
YP
D000017:ABO Blood-Group System / Q000276:immunology; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D004912:Erythrocytes / Q000187:drug effects; D005285:Fermentation / Q000502:physiology*; D006384:Hemagglutination / Q000187:drug effects; D006801:Humans; D010843:Pichia / Q000235:genetics / Q000378:metabolism*; D000519:alpha-Galactosidase / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology
D000017:ABO Blood-Group System; D000519:alpha-Galactosidase