PH-MEDIATED RELEASE OF BETALAINS FROM TRANSFORMED ROOT CULTURES OF BETA-VULGARIS L

Brief exposure of Beta vulgaris root cultures to acidic medium resulte d in release of betalain pigments while the capability for regrowth an d continued pigment accumulation was retained. A 10-min exposure to pH 2 followed by return to standard growth medium (pH 5.5, 1.1 mM PO4) r esulted in release of 0.59 mg pigment/g dry weight over the subsequent 24-h period. The released pigment corresponds to 36.8% of the total p igments. Further improvement in culture productivity was achieved thro ugh phosphate limitation. Specific pigment productivity increased five fold for cultures grown in phosphate-free medium as compared to cultur es grown in control medium (1.1 mM PO4). A maximum total pigment produ ction of 25.2 mg/l was observed at an initial medium phosphate level 0 .3 mM. When combined with phosphate limitation, low pH facilitated the release of 3.03 mg pigment/g dry weight, which corresponds to 50% of the total pigment. The permeabilized roots were capable of regrowth an d continued pigment accumulation. A cytochemical assay for respiratory activity revealed that the basis of regrowth was lateral root initial s that were unaffected during the acidic pH treatment.