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

Abstract

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 µM 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 (½ 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 ½ MS medium with 10 µM 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.