Production of Recombinant Butyrylcholinesterase from Transgenic Rice
Cell Suspension Cultures in a pilot scale bioreactor
Abstract
Producing recombinant proteins in transgenic plant cell suspension
cultures in bioreactors provides controllability, reproducibility,
scalability, and low-cost production, although low yields remain the
major challenge. The studies on scaling-up to pilot-scale bioreactors,
especially in conventional stainless-steel stirred tank bioreactors
(STB), to produce recombinant proteins in plant cell suspension cultures
are very limited. In this study, we scaled-up the production of rice
recombinant butyrylcholinesterase (rrBChE), a complex hydrolase enzyme
that can be used to prophylactically and therapeutically treat against
organophosphorus nerve agents and pesticide exposure, from
metabolically-regulated transgenic rice cell suspension cultures in a
40-L pilot-scale STB. Employing cyclical operation together with a
simplified-process operation (controlling gas sparging rate rather than
dissolved oxygen and allowing natural sugar depletion) identified in
lab-scale (5-L) bioreactor studies, we found consistent maximum total
active rrBChE production level of 46-58 µg/g fresh weight in four cycles
over 82 days of continuous operation. Additionally, maintaining the
overall volumetric oxygen mass transfer coefficient (kLa) in the
pilot-scale STB to be equivalent to the lab-scale STB improves the
maximum total active rrBChE production level and the maximum volumetric
productivity to 85 µg/g fresh weight and 387 µg L-1 day-1, respectively,
which are comparable to the lab-scale culture. Here, we demonstrate
pilot scale bioreactor performance using a metabolically-regulated
transgenic rice cell culture for long-term, reproducible, and sustained
production of rrBChE.