Optimal Operating Conditions for Cultivation of Plant Cells in an External Loop Airlift Bubble Colum

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The present research employed the cultivation of carrot calluses for production of beta-carotene as a model system of plant cell culture and the external loop airlift bubble column as a bioreactor suitable to large scale culture under lower and more uniform hydodynamic shear stress. The purpose of this work is (a) to examine the effects of the various operating conditions on cell growth and beta-carotene production, (b) to determine the optimum of each operating variable taking the content, yield and productivity of beta-carotene as the objective functions, and (c) to establish kinetic model to predict the time courses and to search for an optimal operating condition. The results obtained for each research subject are summarized as follows.1. Effects of bioreactor geometry and operating conditions on cell growth and beta-carotene production of suspended carrot cellsAlthough the optimum values of each operating variable were almost the same for both airlift bioreactor and shaking flask, … More the beta-carotene content and productivity in the former was grater than those in the latter. The production under the combined optimal operating conditions was several times higher than that under the control conditions. The higher temperature favored both growth and production in the earlier stage of cultivation, while the lower ne favored those in the later stage. This suggested a two-phase cultivation shifting the temperature from higher to lower one. The characteristics of airlift bioreactor was also investigated.2. Effects of bioreactor geometry and operating conditions on beta-carotene production of immobilized carrot cellsThe carrot cells immobilized in the three different calcium alginate gel beads gave the lower growth and beta-carotene content than the corresponding suspended cells by factors of 1/2 to 1/3 and 1/5 to 1/10, respectively. The higher molecular weight of the alginates used reduced the growth and enhanced the content to a greater extent. This verified the negative correlation of beta-carotene content with cell growth. A further study on excretion of beta-caratene will be continued by using a novel glycolipid.3. Comparison of various culture methods and search for optimal operating conditionsThe kinetic model assuming an inhibited cell growth and a nonlinear dependence of beta-carotene production on growth well reproduced the observed time courses. The kinetic parameters in the model were correlated with the operating conditions in the dimensionless form based on the respective variables and parameters for the control cultures. The model with the correlations fairly predicted the time courses and the optimal operating conditions. In the solid cultivation on the gellan gum medium, the four different cell lines gave the content of no greater than 1/10 of that for the corresponding suspended cells. This revealed that no great decrease in cell growth due to solid cultivation resulted in a remarkable increase in the content although the negative correlation of content with growth was observed even in the solid cultivation. Less