Production of somatic embryos in a helical ribbon impeller bioreactor

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Abstract
Embryogenic cultures of a transformed Eschscholtzia californica cell line were carried out in a 11‐L helical ribbon impeller bioreactor operated under various conditions to evaluate the performance of this equipment for somatic embryo (SE) production. All bioreactor cultures produced SE suspensions with maximum concentrations at least comparable to those obtained from flask control cultures (∼8–13 SE · mL−;1). However, an increase of the mixingspeed, from 60 to 100 rpm, and low sparging rate (∼0.05 VVM, kL a ∼ 6.1 h−;1) for dissolved oxygen concentration (DO) control yielded poorer quality embryogenic cultures. The negative effects on SE production were attributed mainly to the low but excessive shear experienced by the embryogenic cells and/or embryoforming aggregates. High DO (∼60% of air saturation) conditions favored undifferentrated biomass production and high nutrient uptake rates at the expense of the slower SE differentiation process in both flask and bioreactor cultures. Too low DO (−5–10%) inhibited biomass and SE production. The best production of SE (∼44 SE · mL−1 or ∼757 SE · g dw−1 · d−1) was achieved by operating the bioreactor at 60 rpm while controlling DO at ∼20%by surface oxygenation only (0.05 VVM, kL a ∼ 1.4 h−;1). This production was found to be a biomass production/growth‐associated process and was mainly limited by the availability of extracellular phosphate, magnesium, nitrogen salts, and carbohydrates. © 1994 John Wiley & Sons, Inc.