The Effect of oxygen transfer conditions on recombinant glucose isomerase production by Pichia pastoris under glyceraldehyde-3-phosphate dehydrogenase promoter

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2015
Güneş, Hande
The aim of this study is to investigate effects of oxygen transfer conditions on recombinant glucose isomerase (r-GI) production by Pichia pastoris under glyceraldehyde-3-phosphate dehydrogenase promoter (PGAP). Two different sets of operation strategies were investigated in terms of oxygen transfer conditions. In the first one, aeration rate was kept constant at QO/V = 3 vvm, 6 vvm, and 10 vvm while agitation rate was kept at N = 900 rpm; and in the second one, dissolved oxygen concentration was kept constant at CDO = 5%, 10%, 15%, 20% and 40% air saturation throughout the bioprocesses. In the strategies where oxygen supplementation was relatively high, QO/V = 6 vvm and 10 vvm, excessive abundance of oxygen at the earlier hours of the bioprocesses limited cell growth and GI activity. Regardless of the oxygen transfer conditions, the cell concentration and glucose isomerase activity profiles showed similar trends in each strategy with different highest values. The highest cell concentration was achieved when dissolved oxygen concentration was constant at 20% air saturation as 44 g L-1 at t = 9 h, while the highest recombinant GI activity was achieved when dissolved oxygen concentration was kept constant at 15% saturation as 4440 U L-1 at t = 15 h. The highest overall cell yield on substrate was obtained when the dissolved oxygen concentration was kept at 20% air saturation as 0.48 g cell g-1 substrate, which is the theoretical yield used for the calculation of substrate feeding rate. Lower GI activities were obtained by PGAP compared to alcohol oxidase 1 promoter (PAOX1); however, decrease in fermentation time by more than 3-fold and elimination of methanol usage make PGAP a favorable alternative to PAOX1-driven expression systems.

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Citation Formats
H. Güneş, “The Effect of oxygen transfer conditions on recombinant glucose isomerase production by Pichia pastoris under glyceraldehyde-3-phosphate dehydrogenase promoter,” M.S. - Master of Science, Middle East Technical University, 2015.