High-level production of domain antibodies (dAbs) in recombinant Escherichia coli high cell-density fermentation using chemically defined media

Domain antibodies (dAbs) are emerging as a relatively new class of biopharmaceutical medicine. dAbs are the smallest known antigen-binding sections of variable regions of the heavy and light chains of immunoglobulins, ranging from 11 - 15 kDa. Our dAbs are currently produced in E. coli using complex media, and are secreted into the periplasm and released into the culture medium in a spontaneous manner involving cell lysis.  Lot-to-lot variability in raw materials and inconsistency in spontaneous release of product pose important risks that effect process performance and present significant scale-up challenges. The use of chemically defined media can overcome and/or reduce those issues by recovering the product through controlled cell lysis. We will discuss the approaches taken to express dAbs at high concentrations in E. coli high cell-density fermentation using chemically defined media, an aggressive feed profile, and an altered induction strategy. As a result, the dAbs are retained inside of the periplasm and recovered through controlled cell lysis using homogenization. The highest amount of a soluble dAb product was achieved at 28 g per L of culture. This provides a new approach to solve potential pilot and commercial scale issues and to improve process controllability and consistency.