Modeling of azadirachtin production by Azadirachta indica and its use for feed forward optimization studies

Azadirachtin, obtained from Azadirachta indica (neem) has emerged as wonderful natural biopesticide for pest control due to its efficacy, biodegradability and minimum side effects. To overcome constraints associated with its limited, variable and unreliable supply from natural trees, plant cell suspension culture of A. indica was developed (obtained from callus of seeds). The kinetics of cell growth/azadirachtin formation and substrate consumption of A. indica suspension culture was established in bioreactor with low shear setric impeller under optimized culture conditions (statistically optimized independently). The culture featured a growth of 15.5 and 0.05 g/l azadirachtin in 10 days of cultivation after which azadirachtin concentration declined. To prevent any inhibition caused by the excess feeding of substrate during fed-batch cultivation, inhibition of the carbon, nitrate and phosphate were separately established. Based on batch kinetics/inhibitory data a mathematical model was proposed and model parameters were evaluated. The model was extrapolated to fed-batch cultivation and nutrient feeding strategy (with respect to carbon, nitrate and phosphate) were computer simulated for a suitable fed-batch cultivation of A. indica cells to enhance growth and product formation. Fed-batch cultivation demonstrated a growth of 20.06 g/l biomass and 0.082 g/l of azadirachtin in 14 days of cultivation. A 30% increase in cell growth and 83% increase in azadirachtin production were obtained when a computer simulated feeding strategy was experimentally implemented in 3 l bioreactor.