Suspension cells of Taxus chinensis were cultivated in both shake flasks and bioreactors. The production of taxuyunnanine C (TC) was greatly reduced when the cell cultures were transferred from shake flasks to bioreactors. Oxygen supply, shear stress and stripping-off of gaseous metabolites were considered as potential factors affecting the taxane accumulation in bioreactors. The effects of oxygen supply on the cell growth and metabolism were investigated in a stirred tank bioreactor by altering its oxygen transfer rate (OTR). It was found that both the pattern and amount of TC accumulation were not much changed within the range of OTR as investigated. Comparative studies on the cell cultivation in low shear and high shear generating bioreactors suggest that the decrease of TC formation in bioreactors was not due to the different shear environments in different cultivation vessels. An incorporation of 2% CO2 in the inlet air was beneficial for the cell growth, but did not improve the TC production in bioreactors. Furthermore, the effects of different levels of ethylene addition into the inlet air on the cell growth and TC production were investigated in a bubble column reactor. The average cell growth rate increased from 0.146 to 0.204 d21 as the ethylene concentration was raised from 0 to 50 ppm, and both the content and production of TC were also greatly improved by ethylene addition. At an ethylene concentration of 18 ppm, the highest TC content and volumetric production in the reactor reached 13.28mg/(g DW) and 163.7mg/L, respectively, which were almost the same as those in shake flasks. Compared with the control reactor (bubble column without ethylene supplementation), the maximum TC content was increased by 82% and the total production of TC was doubled. The results indicate that ethylene is a key factor in scaling up the process of the uspension cultures of T. chinensis from a shake flask to a bioreactor.

In conventional suspension cultures of Taxus chinensis, the accumulation of physiologically active taxuyunnanine C (Tc) in 1l (working volume) airlift bioreactors was lower than in shake flasks. Elicitation by methyl jasmonate (MJA) or sucrose feeding could improve the taxane production in the bioreactors.Astrategy of combining MJAelicitation and sucrose feedingwas applied to cell cultures in bioreactors. Both the Tc production and productivity were significantly enhanced by combined addition of 100 M MJA and 20gl−1 sucrose at day 7 and their maximum levels reached were 344±12mgl−1 (day 18) and 18.6±0.5mgl−1 day−1 (until day 15), respectively. A further combination of MJA elicitation (at 100 M), sucrose feeding (at 20gl−1) and ethylene incorporation (at 18 ppm) in the inlet air improved the Tc productivity to 20.2±0.4mgl−1day−1 in the bioreactors. The results suggest that the above combination approach is a useful strategy for large-scale production of taxane diterpenes by plant cell cultures.

Scale-up of a novel centrifugal impeller bioreactor (CIB) was demonstrated for production of valuable plant-specific secondary metabolites by high-density cell cultures. Initial kLa was identified to be a key factor affecting cell growth and production of ginseng saponin and polysaccharide by high-density cultivation of Panax notoginseng cells in a 3-L CIB. A high level of ginseng saponin and polysaccharide production was obtained at an initial kLa value of 30.2 h-1. A maximum dry cell weight (DW) and production titer of ginseng saponin and polysaccharide reached 22.0 (0.3, 1.5

Scale-up of a liquid static culture process was studied for hyperproduction of ganoderic acid (GA) by a famous Chinese traditional medicinal mushroom, Ganoderma lucidum. Initial volumetric oxygen transfer coefficient (KLa) and area of liquid surface per liquid volume (As) were identified as key factors affecting cell growth and GA accumulation in liquid static cultures of G. lucidum, on the basis of which a multilayer static bioreactor was designed. At a low initial KLa level of 2.1 h-1, a thick layer of white mycelia was formed on the liquid surface, and an optimal production of total GA (i.e., GA production in the liquid and on the liquid surface) was obtained. Both the formation of white mycelia and production of GA on the liquid surface were enhanced with an increase of As within the range as investigated (0.24-1.53cm2/mL). At an As value of 0.90cm2/mL, the total GA production reached maximum. A successful scale-up from a 20-mL static T-flask to a 7.5-L three-layer static bioreactor was achieved based on initial KLa. The maximum biomass (20.8