Increased production of digoxin by digitoxin biotransformation using cyclodextrin polymer inDigitalis lanata cell cultures

Addition of β-cyclodextrin (β-CD) polymer during the biotransformation of digitoxin into digoxin using cell suspension cultures ofDigitalis lanata enhanced the conversion yield. Digitoxin showed better adsorption to CD polymer compared to digoxin, so that the optimization of addition time was found to be necessary. In the case of adding CD polymer 24 hours after the feeding of substrate digitoxin, the highest digoxin production could be achieved. At this period, digitoxin was almost consumed by cells and productivity was proportionally enhanced according as the amount of substrate was increased. Immobilization of CD polymer did not promote the biotransformation. When 3.33 g/L of CD polymer was added, 90% and 50% of digitoxin and digoxin was adsorbed respectively. Thus selective inclusion complex formation could be expected. Adsorption rate was found to be rapid and saturation was obtained within 10 hours of contact.