High cell-density expression system: yeast cells in a phalanx efficiently produce a certain range of...

Yeast's extracellular expression provides a cost-efficient means of producing recombinant proteins of academic or commercial interests. However, depending on the protein to be expressed, the production occasionally results in a poor yield, which is frequently accompanied with a deteriorated growth of the host. Here we describe our simple approach, high cell-density expression, to circumvent the cellular toxicity and achieve in a production of a certain range of "difficult-to-express" secretory protein in preparative amount. The system features an ease of performing: (1) precultivate yeast cells to the stationary phase in non-inducing condition, (2) suspend the cells to a small aliquot of inducing medium to form a high cell-density suspension or "a phalanx," and then (3) give a sufficient aeration to the phalanx. Factors and pitfalls that affect the system's performance are also described.