We examined the effects of abiotic (methyl jasmonate [MeJA] and salicylic acid [SA]) and biotic (yeast extract and chitosan) elicitors for improvement of bioactive compounds production on adventitious root cultures in Polygonum multiflorum. The application of yeast extract resulted in significantly (p ≤ 0.05) higher dry root biomass (9.98 g/L) and relative growth rate versus the control. Cultures treated with abiotic elicitors showed higher percentage of dry weight than the other samples. Low concentrations of all elicitors (50 μM MeJA and SA, and 50 mg/L yeast extract) improved secondary metabolite production except for chitosan, whose performance was worse than that of the control. HPLC analysis of various bioactive compounds revealed significantly higher elicitation efficiency for MeJA than for the other treatments, with an approximately 2-fold increase in root dry weight (22.08 mg/g DW) under 50 μM MeJA treatment versus the control (10.35 mg/g DW). We also investigated the feasibility of scaling up the production process by comparing shake flask cultures with 3- and 5-L balloon type bubble bioreactors (BTBB) using 50 μM MeJA as an elicitor. Growth and metabolite accumulation increased in BTBB compared with shake flask cultures. We detected a non-significant difference in biomass productivity between 3 and 5-L BTBB, but the efficiency of bioactive compound accumulation decreased with increasing volume. These findings will be useful for developing a pilot-scale P. multiflorum adventitious root cultivation process for high biomass and bioactive compound production to meet the demands for natural ingredients by the pharmaceutical and cosmetic industries without affecting the natural habitat of this plant.

Hairy root cultures (HRCs) are characterized by fast and unlimited root growth, and they have greater genetic stability than other cultivation methods. HRCs are known to accumulate phytochemical levels comparable to those of intact plant. In this study, HRCs of Polygonum multiflorum were established from leaf explants infected with Agrobacterium rhizogenes strain KCCM 11879. Over 60% of the explants showed hairy root induction after 21 days of cultivation on hormone-free MS (Murashige and Skoog Physiol Plant 15:473-479, 1962) medium; induced roots were confirmed by PCR using a rolC-specific primer. Of the six lines of HRCs selected for further analysis, line HR-01 performed best, producing a root biomass (105.2 g L of FW, 9.7 g L of DW), which is 10-fold higher than that of non-transgenic roots. The HR-01 line also showed a significant increase in its total phenolic content (26.64 mg g DW), while non-transgenic roots accumulated 8.36 mg g DW of total phenolic. The levels of phenolic compounds in the HRCs increased more than 2.5-fold following exposure to 50 μM methyl jasmonate for 5 days. Fourier transform infrared (FT-IR) spectroscopic analysis of bioactive accumulation in P. multiflorum enabled discrimination between hairy root and adventitious root cultures. Thus, it is evident from this study that HRCs could be an attractive proposition for large-scale production of root biomass and secondary metabolites of P. multiflorum in bioreactors.

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Panax ginseng Mayer is a perennial herb that has been used as a medicinal plant in Eastern Asia for thousands of years. The aim of this study was to enhance root biomass and ginsenoside content in cultured adventitious roots by colchicine mutagenesis. Adventitious P. ginseng roots were treated with colchicine at different concentrations (100, 200, and 300 mg·L−1) and for different durations (1, 2, and 3 days). Genetic variability of mutant lines was assessed using random amplification of polymorphic DNA (RAPD) analysis. Ginsenoside biosynthesis gene expression, ginsenoside content, enzyme activities, and performance in bioreactor culture were assessed in four mutant lines (100–1-2, 100–1-18, 300–1-16, and 300–2-8). The results showed that ginsenoside productivity was enhanced in all mutant lines, with mutant 100–1-18 exhibiting the most pronounced increase (4.8-fold higher than the control). Expression of some ginsenoside biosynthetic enzymes was elevated in mutant lines. Enzyme activities varied among lines, and lipid peroxidation activity correlated with root biomass. All four lines were suitable for bioreactor cultivation, with mutant 100–1-18 exhibiting the highest biomass after culture scale-up. The results indicated that colchicine mutagenesis of P. ginseng roots increased biomass and ginsenosides production. This technique, and the root lines produced in this study, may be used to increase industrial yields of P. ginseng biomass and ginsenosides.

Cynanchum wilfordii root is used in traditional herbal medicine owing to its various pharmacological activities. However, C. wilfordii roots are misused owing to their morphological similarities with C. auriculatum. Adventitious root (AR) culture can prevent such misuse, and the selection of plant materials is an important procedure for producing high-quality ARs. This study aimed to compare the proliferation and metabolic profiles of C. wilfordii ARs in two types of explants from different cultivation methods (either cultivated in open field (ECF) or cultivated on a heap of C. wilfordii (ECH)). After 4 weeks of culture, the proliferation rate and number and length of secondary ARs were determined, and 3/4 Murashige and Skoog (MS) salt medium, 4.92 μM indole-3-butyric acid (IBA), and 5% sucrose were suggested as the best proliferation conditions for ARs originating from both ECF and ECH. Through metabolic profiling, ARs from ECH were found to show higher accumulation patterns for flavonoids, polysaccharides, hydroxyacetophenones, aromatic amino acids, and mono-unsaturated fatty acids, which were ascribed to the activation of flavonoid biosynthesis, the phenylpropanoid pathway, and fatty acid desaturase, stimulated by abiotic stresses. In contrast, ARs from ECF had higher levels of TCA cycle intermediates, amino acids in the aspartate–glutamate pathway, and saturated and polyunsaturated fatty acids, indicating energy metabolism and plant development. Overall, the current study provided information on the optimal conditions for inducing C. wilfordii ARs with higher amounts of bioactive compounds.