Features of respiration and formation of steroidal glycosides in Dioscorea deltoidea cell suspension culture grown in flasks and bioreactors

An important task is to monitor the physiological state of the cell population when scaling apparatus cultivation of higher plants’ cell cultures to industrial volumes. Investigations were carried out on the culture of Dioscorea deltoidea Wall—strain producer of steroidal glycosides (protodioscin and deltoside)—for which growth characteristics and content of furostanol glycosides were determined during the semirunning growth in bubble bioreactors (20 and 630 L); total rate of oxygen uptake and the portion of participation of alternative oxidase (AO) in the process were measured in the exponential growth phase. The measurements were performed for 3–4 subculture cycles for each apparatus, starting from the second cycle from the moment of inoculation. The values of oxygen mass transfer coefficients (K La, h−1) for bioreactors were determined at modes of mixing and aeration optimal for growing strain. The maximal portion of cyanide resistant respiration was determined in 20-liter bubble bioreactor with a point aerating device (up to 60–65% of total respiration rate). The minimal values of (K La (2.0–2.4 h−1) were obtained for the same apparatus, as well as lower levels of furostanol glycosides (4.2–8.0% of dry cell weight). Apparently, this effect was due to insufficiently uniform distribution of oxygen in the nutrient medium. Minimal activity of AO (within 15–25%) was noted for the system with more intensive mass transfer of oxygen-in 630-liter bubble bioreactor with the annular aerator (K La 7.1–8.0 h−1). Higher biosynthetic rates (7.7–13.9% of dry cell weight) were found in the same bioreactor.