Optimization of sucrose concentration to promote root proliferation and secondary metabolite accumulation in adventitious root cultures of Ocimum basilicum

Ocimum basilicum L. (sweet basil) is a medicinal herb that contains valuable secondary metabolites belonging to different groups. Therefore, the plant displays a wide range of pharmacological activities. In vitro cultures of sweet basil are a very promising approach to produce bioactive compounds, but studies on optimization of essential medium components are very limited. To the current author's knowledge, there is no previous report on the determination of the optimal sucrose concentration for rosmarinic acid production in adventitious roots of sweet basil in airlift bioreactors. This study aimed to determine the effects of 2.0, 3.0, 4.0, and 5.0% sucrose on rosmarinic acid content, biomass accumulation, and antioxidant activities (DPPH, ABTS, and FRAP) in adventitious root culture of sweet basil under balloon-type bubble bioreactors. Also, phenylalanine ammonia lyase activities (PAL) and accumulation of total phenolic and flavonoid were measured. Additionally, the amounts of some stress parameters (proline, malondialdehyde, and hydrogen peroxide) and the activities of antioxidant enzymes (CAT, POD, and SOD) were measured to assess the levels of sucrose-induced stress and antioxidant defense system. UHPLC-HESI-MS/MS analysis showed that the maximum rosmarinic acid content was determined as 28.11 +/- 0.61 mg g(-1) DW at 2.0% sucrose, which was 1.28, 1.34, and 1.78 times higher than 3.0, 4.0, and 5.0% sucrose, respectively. Similarly, the highest accumulations of fresh weight, total phenolic, and flavonoid were obtained at 2.0% sucrose as 91.46 +/- 1.91 g L-1, 28.83 +/- 0.70 mg g(-1) DW, and 3.26 +/- 0.07 mg g(-1) DW, respectively. In addition, the highest levels of PAL activity and antioxidant activity (DPPH, ABTS, and FRAP) were achieved at 2.0% sucrose. On the other hand, stress parameters and antioxidant enzyme activities of adventitious roots were the lowest at 2.0% sucrose. These results indicated that determination of optimum sucrose concentration is an indispensable parameter for further enhanced production of rosmarinic acid and biomass in adventitious root culture of sweet basil through bioreactors.

Automated summary

This study aimed to determine the effects of different sucrose concentrations on rosmarinic acid content, biomass accumulation, and antioxidant activities in adventitious root culture of sweet basil. The results showed that the optimum sucrose concentration for maximum rosmarinic acid production, fresh weight, total phenolic and flavonoid accumulation, PAL activity, and antioxidant activity was 2.0%. Additionally, stress parameters and antioxidant enzyme activities were the lowest at this sucrose concentration.