PRODUCTION OF SOMATIC EMBRYOS IN A HELICAL RIBBON IMPELLER BIOREACTOR

Embryogenic cultures of a transformed Eschscholtzia californica cell l ine were carried out in a 11-L helical ribbon impeller bioreactor oper ated under various conditions to evaluate the performance of this equi pment for somatic embryo (SE) production. All bioreactor cultures prod uced SE suspensions with maximum concentrations at least comparable to those obtained from flask control cultures (similar to 8-13 SE.mL(-1) ). However, an increase of the mixing speed, from 60 to 100 rpm, and l ow sparging rate (similar to 0.05 VVM, k(L)a similar to 6.1 h(-1))for dissolved oxygen concentration (DO) control yielded poorer quality emb ryogenic cultures. The negative effects on SE production were attribut ed mainly to the low but excessive shear experienced by the embryogeni c cells and/or embryo-forming aggregates. High DO (similar to 60% of a ir saturation) conditions favored undifferentrated biomass production and high nutrient uptake rates at the expense of the slower SE differe ntiation process in both flask and bioreactor cultures. Too low DO (si milar to 5-10%) inhibited biomass and SE production. The best producti on of SE (similar to 44 SE.mL(-1) or similar to 757 SE.g dw(-1).d(-1)) was achieved by operating the bioreactor at 60 rpm while controlling D O at similar to 20% by surface oxygenation only (0.05 VVM, k(L)a simil ar to 1.4 h(-1)). This production was found to be a biomass production /g rowth-associated process and was mainly limited by the availability of extracellular phosphate, magnesium, nitrogen salts, and carbohydra tes. (C) 1994 John Wiley and Sons, Inc.