Plant-based biopharmaceuticals have become more attractive due to several advantages of using whole plants (molecular farming) or plant cells as a production platform. For example, plants do not produce prions, and they are unable to propagate human pathogens like mammalian cells. Plants also provide proper protein folding and complex protein post-translational modifications. Unlike whole plants, plant cell cultures can be grown in low cost chemically-defined media in a contained sterile environment such as a bioreactor, which makes the system controllable, reproducible, and compatible with regulatory guidelines such as current good manufacturing practice (cGMP). However, there are limited studies on scale-up to pilot-scale bioreactors, especially in conventional stainless-steel stirred tank bioreactors (SSTBR), to produce recombinant proteins in plant cell suspension cultures. In this study, we successfully 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 pesticides exposure, from metabolically regulated transgenic rice cell suspension cultures in a 40-L pilot-scale SSTBR. Employing cyclical operation together with the efficient simplified-process operation (controlling gas sparging rate rather than dissolved oxygen and allowing natural sugar depletion) identified in lab-scale bioreactor studies, we found consistent maximum total functional rrBChE production level of 46-58 µg/g fresh weight in four cycles over 80 days of operation. Here we demonstrate the potentially cost-effective and scalable platform for rrBChE production as a result of the simplified bioreactor operation and the low cost of plant cell culture media.

Pilot-scale bioreactor production of recombinant butyrylcholinesterase from transgenic rice cell suspension cultures

ACS Fall 2020 Virtual Meeting

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