Plant Hairy Roots as Biofactory for the Production of Industrial Metabolites

Plants are a rich source of secondary metabolites, and plant cell culture technologies developed in the past are the best possible tool for secondary metabolites production having various importance in the pharmaceuticals, insecticides, dyes and drugs production, food and flavor industries, etc. Medicinal plants are those plants that produce certain compounds that acts as therapeutic agents, nutritional additives or supplements, and toxic agents on several other species including human. Due to strict metabolic regulation and tissue specific localization, differentiated cultures such as hairy root cultures are widely studied. Hairy roots emerge when a plant is infected by a symbiotic bacteria called Rhizobium rhizogenes that is an important method for the production of secondary metabolites synthesized in plant roots. Agrobacterium rhizogenes (or R. rhizogenes ) transforms plant genomes and induce the production of hairy roots that are also known to produce a spectrum of secondary metabolites that are not present in the parent plant. The physical characteristics of hairy root formed are identified by fast hormone-independent growth, lack of geotropism, lateral branching, and their stability at genetic level. Elicitation of hairy roots is the process used to enhance and increase the production of secondary metabolites, and it also helps in forming metabolic pathways for preventing the feedback inhibition and protecting metabolites from degrading in the production media. A. rhizogenes infection in plants causes transformed roots characterized by high growth rate, genetic stability, and growth in hormone free media. In situ adsorption of the products results in the increased yield of the product by many folds. Due to the recent advancements in the field of transgenic research, the possibility of the metabolic engineering of biosynthetic pathways for high-value secondary metabolites production is increased thus improving yields. This adaptability gives hairy roots a name as a platform for major biotechnological tools. In recent years, the use of plants as bioreactors has emerged as an exciting area of research and significant advances have created new opportunities. Development of large-scale culture methods using bioreactors has made production of secondary metabolites easy at the industrial scale. Now these expression systems are ready to be used by different industries like pharmaceutical, cosmetics, and food sectors due to the development of fully controlled large-scale bioreactors. Low production cost, product safety, and easy scale up have been the best characteristics in the rapid growth of plant bioreactors.