Production of betalains from callus and cell suspension cultures of Pereskia aculeata Miller, an unconventional leafy vegetable

Betalains are hydrophilic pigments found in Caryophyllales species, considered important as food colorants, a source of essential amino acids and as a phytomedicine. Pigmented friable calluses were induced from leafy cotyledon and hypocotyl segments of Pereskia aculeata Mill. cultivated on MS basal medium supplemented with 4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid (Picloram). The highest callus biomass accumulation with reddish-pink pigmentation was achieved in cultures initiated from hypocotyl explants on medium supplemented with 10 A mu M Picloram. Instead of improving callus proliferation, the use of Picloram together with either 6-Benzylaminopurine or Kinetin induced cell oxidation. In contrast, the use of half-strength MS medium (A1/2 MS) with Picloram supplementation resulted in the proliferation calli, and the pigments were characterized as betalains. Betalain production was enhanced on modified MS medium (30 mM total nitrogen and 1:4 or 1:8 ratio of NH4 (+)/NO3 (-)). Cell suspension cultures were established in liquid media after transfer of 1 g of betalain-producing calli which had been kept on A1/2 MS medium with 10 A mu M Picloram. After 15 days of culture, cell suspensions achieved eight-fold increase in biomass accumulation. Cell suspensions were maintained through three subcultures for 12-16 days through the exponential growth phase. The in vitro system that induced the highest betalain content and biomass accumulation was achieved from cell suspension cultures on modified MS (1:4 ratio NH4 (+)/NO3 (-)). Therefore, this study established an efficient protocol for betalain and biomass accumulation from callus and cell suspensions of P. aculeata Mill. under the same culture conditions, thus providing a new source of betalain production for commercial purposes.