Agitated cultures and temporary immersion bioreactors are effective modes of cultivation for Reynoutria japonica Houtt. and stimulate synthesis of phenolic compounds

Abstract Reynoutria japonica Houtt. (Japanese knotweed) is an invasive plant belonging to the Polygonaceae family. However, being native to east Asia, it has been used in natural medicine since ages because of broad range of biological activity. Although, R. japonica is known as a rich source of phenolic compounds plant biomass collected from the field may be contaminated with toxic elements like heavy metals. Therefore, the aim of this study was to investigate biomass production and phenolic compounds synthesis in Japanese knotweed from in vitro cultures. Plants were cultivated in a traditional agar-solidified medium, in a liquid medium with rotary shaking (agitated culture), and in a temporary immersion bioreactors Plantform™, as well as in soil (ex vitro conditions). Analyses of the growth index and dry weight accumulation were performed on the collected material. In the extracts obtained from examined plants, qualitative and quantitative analysis of phenolic derivatives using DAD-HPLC was conducted to determine the sum of phenolic compounds, as well as the quantity of selected phenolic acids, catechins and other flavonoids. Results have showed that agitated cultures and temporary immersion bioreactors increased biomass accumulation compared to solid medium cultures. Tissue cultures of R. japonica had increased synthesis of phenolic compounds. Shoots and roots from agitated cultures were 2.8- and 3.3-fold richer in catechins, respectively, compared to plants from ex vitro conditions. Based on the obtained results it can be concluded that agitated and bioreactor cultures are the best source of Japanese knotweed biomass rich in valuable secondary metabolites.