Browsing by Author "Thakore, Dhara"

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Mass production of Ajmalicine by bioreactor cultivation of hairy roots of Catharanthus roseus
(Elsevier B.V., 2017) Thakore, Dhara; Srivastava, Ashok Kumar; Sinha, Alok Krishna
Catharanthus roseus has been known to produce Ajmalicine which is used for treatment of circulatory disorders. Significantly low content of the drug in the natural plant necessitates development of alternative production protocols. Hairy root propagation was considered as a viable alternative. Mass cultivation of the hairy root culture was attempted in several bioreactor configurations; Bubble column, Rotating drum bioreactor, Modified Bubble column with polypropylene (PP) mesh support and Modified Bubble column with Polyurethane foam (PUF) support. Important factors like medium composition, inoculum density, illumination period and aeration rates were optimized before mass propagation of hairy roots. From the data gleaned, the cultivation in rotating drum bioreactor resulted in ajmalicine content of only 4.6 ± 0.4 mg/l. However, the ajmalicine concentration surpassed even that obtained in shake flask (with 34 ± 2.3 mg/l) in a customized bioreactor wherein the hairy roots were anchored onto a polyurethane foam, the highest reported in this scale of cultivation.
Model based fed batch cultivation and elicitation for the overproduction of ajmalicine from hairy roots of Catharanthus roseus
(Elsevier B.V., 2015) Thakore, Dhara; Srivastava, Ashok K.; Sinha, Alok Krishna
Batch cultivation of Catharanthus roseus hairy roots was attempted in a statistically optimized nutrient medium. This resulted in a biomass growth of 5.12 ± 0.46 g/l and ajmalicine content of 24.9 ± 1.2 mg/l on day 30 beyond which the product concentration declined. Using the observed batch kinetics data a mathematical model was developed which could describe the experimental observations to the extent of 99% accuracy as demonstrated by the statistical validity test. The model was thereafter extrapolated to fed-batch cultivation to identify suitable nutrient feeding strategies (by off-line simulations) for the overproduction of ajmalicine. Eventually the experimental implementation of three such feeding strategies and comparison with the model predictions further reinforced the efficacy of the mathematical model under dynamic fed batch conditions. A 60% increase in ajmalicine overall productivity and a 2.5 fold increase in volumetric yield was obtained by the “increasing feed rate strategy” as opposed to batch cultivation. To further improve the alkaloid accumulation a combination of statistically optimized mixture of elicitor(s) (jasmonic acid, methyl jasmonate and KCl) was added after the termination of model based increasing fed batch cultivation which resulted in a significantly high ajmalicine concentration of 123.2 ± 8.63 mg/l (a 4 fold increase compared to batch). This is the first report of such a strategy for overproduction of ajmalicine in rather complex hairy root cultivation.