Process characterization using multi-bioreactor for hCTLA4Ig production in transgenic rice cell cultures

초록

Most of the technical know-how and experience of bioreactor engineering is applicable to plant cell cultures and there are several factors which are related to bioreactor design and operating strategies. Plant cell suspension cultures have more complex rheology due to the formation of large aggregates with various sizes and are more difficult to mix than the other expression systems. Nevertheless, there are few reports regarding the bioreactor operations in transgenic plant cell cultures for the production of plant-made biopharmaceuticals (PMPs). In this study, transgenic rice cell cultures using RAmy3D promoter were used for the production of human cytotoxic T-lymphocyte antigen 4-immunoglobulin (hCTLA4Ig). However, the promoter is induced by sugar depletion, so it causes rapid cell death. In process aspect, the rice cells during production phase are influenced strongly by hydrodynamic stresses such as shear stress and bubble burst. Therefore, for the process characterization, effects of agitation and aeration rates on the cell growth and the production of hCTLA4Ig were investigated. Operating ranges of each parameter were studied in a multi-bioreactor. At various agitation rates, the maximum hCTLA4Ig levels reached 21.1, 21.6, 10.5, and 4.0 mg/L at 80, 160, 240, and 320 rpm, respectively. Among various aeration rates (0.05, 0.1, 0.2, 0.3, and 0.4 vvm), 0.2 vvm provided the best results in hCTLA4Ig level and the specific productivity, and those values were 16.8 mg/L and 0.65 mg/L/day, respectively. Then, their combination experiment was performed in production phase without cell growth. At higher aeration rate (0.3 vvm) regardless agitation rates, the relative cell viability decreased sharply 2 days earlier than those of lower aeration rates. Also, it was confirmed that specific yields and specific productivity at 0.3 vvm were superior to those at 0.05 vvm. Overall, higher aeration rate showed the improved hCTLA4Ig production.