Date of Award
Doctor of Philosophy
Cyclosporin-A (CyA), a secondary endocellular metabolite of the fungus Beauveria nivea ATCC 34921, is an immunosuppressant peptide used worldwide in human organ transplant operations. CyA has also been successfully used to treat a number of autoimmune diseases and parasitic infections. While a great number of papers are published each year about medical applications and mode of action of CyA, however, limited information is available regarding the production of CyA.;This work was divided into two sections: the first dealt with the optimization of medium in shake flasks and the second with the development of fermentation strategies to further increase the volumetric productivity of Cyclosporin-A in a 14-L bioreactor unit.;A new medium was developed that resulted in 222 mg of CyA per litre of fermentation broth in shake flasks. This corresponded to the yield of 14.8 mg CyA/g mycelial dry weight. Fructose concentration higher than 30 g/L inhibited the production of CyA.;Different fed-batch strategics were applied to increase the volumetric productivity of CyA in a 14-L bioreactor. A nicotinamide adenine dinucleotide (NADH) fluorosensor, interfaced with a computer, was used to monitor the growth of the fungus B. nivea. Mathematical models were developed to relate the fluorescence intensity with biomass and fructose concentrations in the bioreactor. The most successful fed-batch fermentation strategy involved a continuous feeding of substrate at the rate of substrate consumption for 48 h, after the fructose concentration in batch mode had dropped down to 5 g/L. The substrate feed rate was then switched to the maintenance level for the next 72 h of fermentation. This strategy gave the highest CyA concentration of 504 mg CyA/L with a yield of 15.14 mg CyA/g mycelial dry weight. This is the highest concentration of CyA reported in the literature using the wild strain of B. nivea ATCC 34921.;This study also demonstrated that by monitoring in situ fluorescence of NADH, a fed-batch strategy can be developed by correlating it to the biomass and the substrate concentrations in the fermentation broth.
Chahal, Parminder Singh, "Fluorosensor-controlled Fed-batch Production Of Cyclosporin A From Beauveria Nivea" (1992). Digitized Theses. 2389.