The Effects of Operating Parameters on Cell Growth and Alkaloid Production in a Novel Plant Cell Membrane Reactor

Abstract

A novel plant cell membrane reactor has been developed for use in secondary metabolite production by plant cell cultures. Inoculated cells (50 g, fresh weight) were immobilized in a 3mm layer on the membrane (130 cm2). Medium (400 mL per batch run) was recirculated in a closed loop underneath the membrane. Cells were supplied with liquid nutrients by medium which permeated the membrane diffused into the cell layer. The cells obtained oxygen from the gas phase which surrounded the inoculated layer. Secondary metabolites which were produced and excreted diffused from the cell layer through the membrane into the medium recirculation stream and were detected by off-line HPLC. The membrane used was a Celgard K-381 polypropylene sheet (Hoechst-Celanese, Wiesbaden, W-Germany) with the following properties: effective pore size 0.075 m, porosity 45%, and thickness 25 ± 2.5 m. The membrane was surfactant treated by the manufacturer. This system was applied to Coffea arabica cells. The cells produce theobromine and caffeine as secondary metabolites. The effects on alkaloid formation can be summarized as follows: 1) glucose had no effect on alkaloid formation, 2) reduction of micro- and macronutrients by 50% reduced alkaloid formation by 60%, 3) adding 50% oxygen to the gas stream reduced alkaloid formation by 40%, and 4) adding 50% nitrogen to the gas stream reduced alkaloid formation by 25%.