Overcoming Oxygen Limitation in High Density Cell Culture by Expression of a Vitreoscilla Hemoglobin (VtHb) Gene

Abstract

Vitreoscilla hemoglobin (VtHb) has been expressed in Saccharomyces cerevisiae, and its influence on yeast growth has been investigated. An expression vector was constructed to express VtHb under the control of GPD promoter and GAL7 terminator. The expression of a VtHb gene (460 bp) and a protein product (15.8 kDa) in recombinant strain was shown by colony PCR and Western blot analysis, respectively. Batch cultivations were performed at 30°C and 200 rpm with a constant air flow rate of 2 vvm in YEPD medium until 48 hr. The recipient strain showed a typical sigmoidal growth curve with the entry of stationary phase after 9 hr of cultivation. However, the recombinant strain exhibited the continuous growth until 26 hr and it reached the cell density of O.D. 19 at 600 nm, which corresponded to 50 % increase of cell mass compared with the recipient strain. These results suggest that the yeast strain can be engineered to have better growth even in the oxygen limited condition by the expression of VtHb.