Bioreactor for cultivation of red beet hairy roots and in situ recovery of primary and secondary metabolites

To arrive at an appropriate bioreactor design and in situ recovery of the products,
red beet hairy roots were used as a model system where the levels of betalain
pigments (betacyanins and betaxanthins) were followed as secondary metabolite
and the peroxidase enzyme as primary metabolite. Medium volume and other
kinetic parameters were found to play significant roles by way of directly affecting
the biomass yield rather than a specific metabolite. The hydrodynamic stress created
on the roots by large culture volume could be minimized by pulse-feeding of
medium in shake-flasks; and by separating the biomass chamber from the aerated
medium reservoir in circulatory fed-batch bioreactor. Accordingly the bioreactor
was modified to provide anchorage and air-enrichment chamber which resulted in
higher formation of both the metabolites than in shake-flasks. Various down-stream
processing aspects such as in situ release of pigments by non-destructive methods,
followed by adsorption through a column and recovery by desorption were optimized
for betalains. A strategy for simultaneous recovery of pigment and peroxidase
was worked out using aqueous two phase extraction (ATPE).