Repeated harvest of vacuole-located secondary product from in vitro grown plant cells using 1.02 MHz ultrasound

Beta vulgaris L. (red beetroot) cells from a suspension culture were sonicated with continuous wave ultrasound (1.02 Mhz) for periods ranging from 10 s to 60 s. In general, cells sonicated for greater than or equal to 30 s released vacuole-located pigment into the surrounding medium, whereas cells sonicated for < 30 s and control (unsonicated) cells released no pigment. Sonicated cells were viable as determined using fluorescein diacetate; microscopic examination of a selected population of sonicated cells did not show any signs of obvious structural damage. Sonicated cell samples were subcultured to re-establish actively growing, pigment-competent cell cultures. Cells from such cultures were available for further harvests of the pigment by sonication. For sonication periods greater than or equal to 50 s, repeated cycles of sonication and incubation allowed pigments to be harvested from cells every 7 days during a 21-day culture period.