Growth and Biosynthetic Characteristics of Phlojodicarpus sibiricus Cell Suspension Cultures

Features of the growth and qualitative composition of secondary metabolites in two lines of suspension cell cultures of Phlojodicarpus sibiricus (Steph. ex Spreng.) K.-Pol., an endangered endemic species of Eastern Siberia, have been studied. A suspension cell culture of leaf origin demonstrated the best growth characteristics, which included growth indices for different criteria (dry and crude biomass and cell concentration): I = 10–14; specific growth rate μ = 0.3–0.4 day –1 ; the maximum dry biomass accumulation М = 9.6 g/L and economic coefficient Y = 0.29. A plant cell culture derived from a hypocotyl was characterized by lower growth parameters: I = 3.6–4.9, μ = 0.12–0.18 day –1 , M = 6.6 g/L, Y = 0.16. Differences in the growth of the studied cultures correlated with the cell aggregation level: the “leaf” culture consisted mainly of small-size aggregates (10–30 cells), whereas the “hypocotyl” culture was presented by large aggregations (50 cells or more). The instrumental cultivation of the small-aggregated suspension cell culture of leaf origin was carried out using two types of laboratory bioreactors (bubble column and stirred tank). Cultivation in a bubble column reactor improved the basic growth characteristics of the cell culture: the growth index for the dry biomass I = 12.7; dry biomass productivity P = 0.78 g/L day, μ = 0.18 day –1 , М = 15.8 g/L, Y = 0.49. In the case of a stirring tank reactor, all growth parameters were decreased, which was probably connected with the cell damage with stirring devices. Additionally, a phytochemical analysis of the secondary metabolite composition in the studied cell cultures was carried out in comparison with the root cells of intact Ph. sibiricus plants. Significant differences in the composition of phenolic compounds were revealed between in vitro cell cultures and plant roots. In the case of cell cultures, polar (hydrophilic) compounds belonging to phenolic derivatives (coumarin glycosides and benzofurans) prevailed. In roots, the main components were more hydrophobic (khellactone ethers). The obtained results confirmed the earlier developed concept of differences in the secondary metabolism of in vitro and in vivo plant cells.