GROWTH OF PLANT-ROOT CULTURES IN LIQUID-DISPERSED AND GAS-DISPERSED REACTOR ENVIRONMENTS

The growth of Agrobacterium transformed ''hairy root' cultures of Hyos cyamus muticus was examined in various liquid- and gas-dispersed biore actor configurations. Reactor runs were replicated to provide statisti cal comparisons of nutrient availability on culture performance. Accum ulated tissue mass in submerged air-sparged reactors was 31 % of gyrat ory shake-flask controls. Experiments demonstrate that poor performanc e of sparged reactors is not due to bubble shear damage, carbon dioxid e stripping, settling, or flotation of roots. Impaired oxygen transfer due to channeling and stagnation of the liquid phase are the apparent causes of poor growth. Roots grown on a medium-perfused inclined plan e grew at 48 % of gyratory controls. This demonstrates the ability of cultures to partially compensate for poor liquid distribution through vascular transport of nutrients. A reactor configuration in which the medium is sprayed over the roots and permitted to drain down through t he root tissue was able to provide growth rates which are statisticall y indistinguishable (95 % T-test) from gyratory shake-flask controls. In this type of spray/trickle-bed configuration, it is shown that dist ribution of the roots becomes a key factor in controlling the rate of growth. Implications of these results regarding design and scale-up of bioreactors to produce fine chemicals from root cultures are discusse d.