Current status of using bioreactors to produce secondary metabolites from medicinal and aromatic plants

Interest in medicinal and aromatic plants (MAPs) has always been very high due to their secondary metabolites. These compounds have relevance in several fields, in pharmaceutical and cosmetic applications and for the food industry. The use of MAPs has a long history, and, in several cases, the cultivation, harvesting, and processing techniques are still based on traditional methods. However, these methods do not always ensure the high quality and quantity of compounds of interest. Moreover, several species of interest are at risk of extinction, or their production and usage are not sustainable from both an environmental and economic point of view. Many bottlenecks can be balanced thanks to the use of bioreactors: in this systems, growing conditions can be adjusted to culture the plants or its organs and to stimulate the metabolic pathway of interest, whit no influence by external factors. Bioreactors ensure high-quality produce that can be employed in pharmaceutical applications or in the food industry, such as food flavor or additives. Moreover, extraction of bioactive compounds from plants can be difficult while production in bioreactors can overcome this issue. For all this reasons, in recent years, the interest in bioreactor application for MAPs has increased: a query in the Scopus database reports 221 results from 1990 to 2021 related to the search keywords “bioreactors” and “medicinal plant” or “aromatic plant”, while 149 records have been found in WoS with the same parameters. Based on this inquiry, the present work aimed to select the most promising applications of bioreactors to produce secondary metabolites of interest from MAPs. In this work, specific fields of application are discussed with the use of bioreactors (e.g., plant cell suspension, hairy, and adventitious root cultures) from promising scientific works.