PRODUCTION OF SUPEROXIDE-DISMUTASE FROM PLANT HAIRY ROOTS BY CONSIDERING THE EFFECT OF NITROGEN-SOURCE IN THEIR CULTURES

The plant hairy roots derived from pak-bung and horseradish were found to possess high activity of superoxide dismutase (denoted as SOD). Based on an examination of the effect of nitrogen source in these hairy root cultures, NH4+ in medium had an inhibitory effect on hairy root growth. It was possible to express the growth properties of hairy roots by a kinetic formula with the term of noncompetitive inhibition by NH4+ and the branching growth model of hairy roots. High growth rates of hairy roots were obtained in the medium with NO3- as nitrogen source. However, the presence of NH4+ in the medium resulted in enhanced SOD activity in the hairy root cells. Thus a two-step culture of pak-bung hairy root was performed, wherein the culture was divided into two phases: cell growth phase in the medium with NO3- and SOD production phase in the medium with NH4+. In this culture system the SOD productivity was 5-7 times that in a culture with medium containing only NO3- as a nitrogen source.