Culture condition optimization and FT-IR analysis of Polygonum multiflorum Thunb. adventitious root cultures grown in an air-lift bioreactor system

Bioreactor cultures have been used for biomass production and bioactive compounds accumulation in adventitious root cultures of medicinal plants. In this study, we evaluated the effects of different auxin types [indole-3-butyric acid (IBA) and 1-naphthaleneacetic acid (NAA)] and concentrations (0.5, 1.0, 2.0 and 4.0 mg·L −1 ), Murashige and Skoog (MS) medium salt strength (0.25, 0.5, 0.75, 1.0, 1.5 and 2X), and sucrose concentrations (0, 1.5, 3, 5, 7 and 10%) on Polygonum multiflorum Thunb. adventitious root cultures in a 3-L balloon-type bubble bioreactor (BTBB). IBA (1, 2, and 4 mg·L −1 ) was more effective than NAA in promoting root growth. Additionally, low MS salt strength (0.25 and 0.5X MS) increased the accumulation of total phenolics and flavonoids but reduced biomass accumulation. Four weeks of culture in full-strength MS medium supplemented with 2 mg·L −1 IBA and 5% sucrose resulted in the highest root biomass [98.46 g·L −1 fresh weight (FW); 13.46 g·L −1 dry weight (DW)] and bioactive compounds accumulation (total phenolics compounds, 53.08 mg·g −1 DW; total flavonoids, 25.10 mg·g −1 DW). To determine whether metabolic fingerprinting of whole-cell extracts could be used to compare metabolic equivalence of P. multiflorum root samples, we treated adventitious roots with different culture conditions, and analyzed the treated adventitious roots and natural roots by Fourier transform infrared (FT-IR) spectroscopy. The results showed that the metabolic pattern of adventitious root samples was similar under different culture conditions; however, these samples could be discriminated from each other in pilot-scale bioreactors. Overall, our study provides useful information for industrial-scale cultivation of P. multiflorum adventitious roots. Key message The optimum condition for bioreactor culture of Polygonum multiflorum is full-strength MS medium supplemented with 2 mg·L-1 IBA and 5% sucrose after 4 weeks of culture. FT-IR analysis can rapidly discriminate among root samples based on total metabolite equivalence.