A PLANT-CELL BIOREACTOR WITH MEDIUM-PERFUSION FOR CONTROL OF SOMATIC EMBRYOGENESIS IN LIQUID CELL-SUSPENSIONS

The Braun Biostat BF2 bioreactor system employs a novel aeration and a gitation system, designed to enhance gaseous exchange and reduce shear stresses on submerged cell suspension cultures. The Biostat BF2 biore actor employs a central pivoting spindle, around which the aeration tu bing is wound forming a large paddle-type structure suspended from the top-plate and swung in a circle by a solid-state magnetic stirrer. Th e aeration tubing is a polypropylene capillary membrane, which has a u nique microporous structure and is ideal for aeration, permitting two- way, bubble-free, gaseous exchange of the medium. This tubing can be r endered porous and can be used in the perfusion of aqueous solutions, enabling cell-free media exchange to be conducted. Thin-walled silicon e rubber tubing, although gas permeable to a degree, cannot be made po rous to aqueous solutions. The bioreactor was inoculated with a suspen sion culture of Sitka spruce (Picea sitchensis [Bong.] Can.) known to be embryogenic and capable of maturing to plantlets on solidified medi um. The perfusion capability of the bioreactor was employed to replace the inital proliferation medium with maturation medium in order to in duce the development of the somatic embryos in submerged cell culture. The size ratio of the somatic embryo heads was monitored over 7 weeks . This cell line was found to mirror just the initial elongation, prev iously observed in shake-flask culture.