Agrobacterium rhizogenes-mediated hairy-root cultures are a very promising alternative to the biotechnological exploitation of plant cell cultures. Their characteristic capacity for secondary-metabolite production, inherent genetic stability reflected in stable productivity and the possibility of genetic manipulation to increase biosynthetic capacity have initiated a considerable interest, both as a fundamental research tool and as a source of valuable products. One of the most important limitations for the commercial exploitation of hairy roots is the development of technologies for large-scale culture. Though these roots have been grown in various bioreactors--stirred-tank, bubble-column, airlift or submerged, trickle-bed and nutrient mist--the question as to which of these alternatives can be successfully and economically scaled-up has yet to be definitively answered. This present minireview highlights various perspectives of hairy-root cultures, describes a comparative scale-up study and discusses various aspects of these cultures when grown in various bioreactors for the production of secondary metabolites.
In this study, we designed a strategy for selecting the operating conditions of a mist reactor for the growth of hairy roots. This was accomplished by developing a mathematical model to optimize the ON/OFF mist duty cycle for the specified growth of hairy roots. The availability and rate of transport of nutrients to the roots are important parameters in the design and operation of the reactor. The thin liquid film over the root surface, which continuously builds up during the ON cycle, is a major factor that limits mass transfer. The same film also acts as a finite reservoir of nutrients in the absence of any replenishment during the OFF cycle. This reservoir gets depleted as growing roots continue to consume the nutrients. As a result of this depletion the duration of the OFF cycle must be limited such that the nutrient concentration does not go below the critical value required for the specified growth rate. The depleted reservoir is then replenished during the next ON cycle to an extent that depends on feed concentration and duration of the next ON cycle. It was shown that the use of increasing feed concentrations in the fed-batch mode of operation could maintain a specified growth rate in the reactor. Interestingly, this also resulted in the efficient operation of the reactor whereby the reactor operated at slightly above the required concentration and close to the point of minimum mass transfer resistance. © KSBB
Hairy root culture is a promising route for large-scale secondary metabolite production. A discrete model is developed to study the kinetic growth of these valuable roots in a reactor. The growth process is defined to occur in three sequential phases. The elongation rate is modeled as exponential growth with the growth coefficient being dependent on mass transfer coefficient, nutrient concentration difference, and distribution of nutrients in growth and sustenance requirements. Results indicate that the primary root growth is reduced by one-fifth of its initial growth rate due to the branching process, and the growth of new branches is significantly faster than its primary root growth due to internal transport of nutrients. The model is successfully validated against experimental findings. Its integration with spatio-temporal variation of nutrients in a reactor will be a crucial input to large-scale production of hairy roots.
This paper presents feasible range of feed concentration and flow rate for sustained operation of nutrient mist reactor (NMR) in continuous mist feed mode for growing hairy roots. Sustained operation of NMR requires liquid holdup in the root bed that does not exceed a critical value and the nutrient concentration in the bed is maintained above a critical value. This ensures that the growing root mass gets adequate supply of both liquid and gas phase nutrients. These bounds on liquid holdup and concentration can be translated to bounds on the feed flow rate and concentration through mass balance over the root bed and numerical simulations. This approach maintains the reactor performance for a continuous mist-on cycle and does away with the uncertainty in choosing intermittent mist-on/mist-off cycles. It is expected that this paper will be of immense help in the rapidly growing NMR technology to grow hairy roots.
Background: (50 mg BD) and pentoxifylline (400 mg TDS) therapy in patients with PVD. Additionally, the adverse effects and economic burden of the combination was taken in to account. Methodology: An Observational antegrade study was done among 100 patients. A Patient with PVD visited to OPD of the vascular department was enrolled in the study. Data was collected as per the Case Record Form. Results: The mean age was found to be 58.4 ± 11.3 years of total 100 patients. An improvement in a Doppler testing (follow-up at the time interval after 1 month, 3 months and 6 months) and increased in peak systolic velocity in distal vessels as well as collaterals were observed in all patients. The PVD was prevalent in 50 to 60 years of age groups and hypertension and smoking were the most common risk factors present in PVD patients. There was more than 70% increase in walking distance after 24 weeks of treatment. Headache 24 (36.4%) and Dizziness 9 (13.6%) were observed as common side effect of therapy. The total cost of the combination therapy was affordable with improved quality of life. Conclusion: The combination treatment showed symptomatic improvement in peripheral vascular disease in the study. The peak systolic velocity gradually increased in the distal vessel and the combination was found to be cost-effective.
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