Yield enhancement of phytochemicals by Azotobacter chroococcum biotization in hairy roots of Arnebia hispidissima

• Hairy roots of Arnebia hispidissima were biotized first time with five strains of Azotobacter chroococcum.
• Nitrogenase activity, dry matter contents, total nitrogen contents were significantly enhanced 2–3 times by biotization of hairy roots.
• The accumulation of propionylalkannin was higher (3 times) in biotized hairy roots.

The biological nitrogen fixation is an essential process and occurs in plants by the nitrogenase activity, which exists as a complex metalloenzyme composed of two easily separable components. The hairy roots of Arnebia hispidissima were regenerated by the infection of Agrobacterium rhizogenes (ATCC 15834). These regenerated hairy roots were biotized with selected five strains of Azotobacter chroococcum. The biotization was developed for the enhancement of the yield of medicinally important alkannin and shikonin derivatives. The nitrogenase activity (96 ± 0.381 nmol C2H4 hairy root−1), fresh weight (58 ± 0.340 mg hairy root−1) and dry matter contents (21 ± 0.349 mg hairy root−1)), total nitrogen contents (24 ± 0.635 mg hairy root−1)) and concentration of phytochemicals were significantly enhanced 2–3 times more in biotized hairy roots while these contents were lower in the hairy roots of control group. The accumulation of propionylalkannin was reached its maximum peak (86 ± 0.290 mg/g fraction) at the cell density of 105 CFU ml−1 on the 11th day of harvesting of biotized hairy roots of A. hispidissima. The observed results provide novel approach into the application of A. chroococcum for the yield enhancement of alkannin and shikonin derivatives in hairy roots of A. hispidissima.

The five strains of Azotobacter chroococcum (ATCC 9043, BCRC 10599, CCRC 10599, DSM 2286, and IAM 12666) were investigated for the establishment of biotization studies in hairy roots for the enhancement of medicinally important secondary products. From the results, it was evidenced that A. chroococcum (ATCC 9043) enhanced the maximum yield of all the isolated naphthaquinones (I to VI) in the Arnebia hispidissima hairy roots by the biotization, while other strains moderately increased the accumulation.Figure optionsDownload as PowerPoint slide