Kinetics of Red-Pigment Fermentation by Monascus Purpureus FTC 5391 in Shake Flask Culture and Stirred Tank Fermenter Using Different Carbon and Nitrogen Sources
Abdul Manan, Musaalbakri (2005) Kinetics of Red-Pigment Fermentation by Monascus Purpureus FTC 5391 in Shake Flask Culture and Stirred Tank Fermenter Using Different Carbon and Nitrogen Sources. Masters thesis, Universiti Putra Malaysia.
A newly isolated red-pigment producing fungus from local source was identified using Microbial Identification System based on fatty acids profiles. Growth morphology and structure of the fungus were also identified using Scanning Electron Microscope. Monospore isolation technique was performed to obtain the improved strain that has high and consistent ability to produce red pigment. Kinetics of red-pigment fermentation by this local strain, identified as Monascus purpureus FTC 5391, in 500 mL shake flask culture and 2 L stirred tank fermenter using different carbon and nitrogen sources were also investigated. From scanning electron microscope examination, M. purpureus FTC 5391 exhibited reproduction characteristics by sexually formation of cleistothecium with ascospores and also asexual formation of conidia. The ability of M. purpureus FTC 5391 wild strain in producing red pigment was successfully improved using monospore isolation technique. By using this approach of improvement, three different monospore isolates of M. purpureus FTC 5391 (MP 3, MP 4 and MP 5) were obtained as the best red-pigment producers when glucose, potato starch and rice starch were used as carbon source, respectively. For subsequent experiments on the development of red-pigment fermentation using glucose as a basal medium, M. purpureus FTC 5391 MP 3 was employed. Among the different nitrogen sources investigated ((NH4)2HPO4, (NH4)H2PO4, NaNO3, NH4NO3, (NH4)2SO4, (NH4)2S2O8, (NH4)Cl, peptone, yeast extract, monosodium glutamate, urea and tryptone, where monosodium glutamate was found to be the preferred nitrogen source for growth of M. purpureus FTC 5391 and red pigment production. From medium optimization studies, medium consisted of 50 g/L glucose and 12 g/L of monosodium glutamate with the addition of trace elements [K2HPO4 (2.5 g/L), KH2PO4 (2.5 g/L), MgSO4.7H2O (1.0 g/L), KCl, (0.5 g/L), ZnSO4.7H2O (0.01 g/L), FeSO4.7H2O (0.01 g/L) and MnSO4.H2O (0.03g/L)] was found optimal for red-pigment production by M. purpureus FTC 5391. On the other hand, optimal fermentation conditions for red pigment production in 2 L stirred tank fermenter were obtained at initial pH 6.5 with agitation speed of 600 rpm, and dissolved oxygen tension (DOT) was maintained at high level (>30% saturation) throughout the fermentation. The experimental data from batch fermentation were analysed in order to form a kinetic model of the process. The unstructured model based on logistic and Leudeking-Piret equations was found suitable to describe growth, substrate consumption and red pigment production by M. purpureus FTC 5391. The maximum specific growth rate (µmax) of 0.055 h-1 and 0.065 h-1 were obtained from simulated modeling of M. purpureus FTC 5391 during growth in shake flask and 2 L stirred tank fermenter, respectively. The maximum red pigment and cell concentrations obtained in batch fermentation using 2 L stirred tank fermenter (20.63 UA500 and 13.2 g/L) and using shake flask (9.26 UA500 and 11.425 g/L) with overall productivity (P) was 0.122 UA500/h and 0.055 UA500/h, respectively. The production of red-pigment by M. purpureus FTC 5391 appeared to be a non-growth associated process; where by rapid red-pigment production occurred during non-growth phase after the depletion of glucose in the medium and the on-set of ethanol accumulation. It seemed that the red-pigment was formed from the metabolism of ethanol accumulated in the culture.
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