Effect of methanol concentration on the production of human beta(2)-glycoprotein I domain V by a recombinant Pichia pastoris: A simple system for thecontrol of methanol concentration using a semiconductor Gas Sensor

The methylotrophic yeast Pichia pastoris is one of the best hosts for the p roduction of foreign proteins because of the presence of the strong AOX1 pr omoter induced by methanol. Methanol feeding during the production phase of the foreign proteins is important because methanol not only induces protei n production but also provides energy source for the host cells. Excess met hanol inhibits the growth of host cells, while an insufficient amount of en ergy source and/or methanol starvation lead to poor growth and production. We constructed a simple methanol control system consisting of a semiconduct or gas sensor and a relay. Using this system, we studied the effect of meth anol concentration on the production of a model foreign protein, human beta (2)-glycoprotein I domain V. The methanol concentrations were kept constant at 1.5, 10, 17, or 31 g.l(-1) (+/-5%) during the production phase. Althoug h the specific rates of growth and methanol consumption decreased with incr ease in the methanol concentration, the specific production rates increased , indicating that the energy for the production competed with that for cell growth. Accordingly, we provided glycerol as an extra energy source during the production phase, with the result that the specific production rate in creased two times. Our simple and inexpensive system will help bioengineeri ng studies on the production of recombinant proteins in P. pastoris, the gr owth and production of objective proteins in which are dependent on the met hanol concentration.