Carrot hairy roots (Daucus carota L.) characterisation and optimisation for high β-carotene extraction

Abstract

Hairy roots are widely known as a biological system for the production of highly diverse biomolecules. β-carotene - a precursor for vitamin A - is known to be an anti-oxidant and anti-gastric cancer and protection agent against cardiovascular disease, heart disease and stroke. β-carotene has been chemically synthesised and consumed by humans. However, the chemical process often produces a by-product that may be harmful to human health. Therefore, this study established a protocol to induce hairy roots (HRs) from a Vietnamese carrot variety and produce natural β-carotene. The Rhizobium rhizogenes ATCC15834 harbouring Ri plasmid and a Vietnamese carrot variety were used as materials for genetic transformation and HR induction studies. The result showed that approximately 50 HR lines were obtained. Culture medium supplemented with 30 mg/L of sucrose that gave the highest biomass of HR was shown in carrot HR line 30, which had a doubling time of 6.5 days. The highest content of β-carotene extraction, at 128 mg/100g hairy roots, was achieved with a ratio volume (v/v) of 2-propanol and plant samples of 20:1, followed by two hours' incubation with 2-propanol at 60°C. Our study reveals a highly efficient protocol for Vietnamese carrot hairy root establishment and multiplication. A very efficient protocol for β-carotene extraction from the hairy root was established to produce natural β-carotene that achieves the same β-carotene quantity as that produced by normal roots. This study provides new insight into the production of high-content and natural β-carotene for therapeutic application.