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Influence of oxygen transfer on benzaldehyde lyase production by recombinant Escherichia coli BL21(DE3) pLySs

Angardi, Vahideh
In this study, the effects of oxygen transfer conditions on the synthesis of the enzyme benzaldehyde lyase as intracellular in recombinant E. coli BL21 (DE3) pLysS was investigated sistematically and a comprehensive model was developed to determine benzaldehyde lyase activity. For this purpose, the research program was carried out in mainly two parts. In the first part of study, the effects of oxygen transfer together with the mass transfer coefficient (KLa), enhancement factor E (=KLa/KLao), volumetric oxygen transfer rate, volumetric and specific oxygen uptake rates, mass transfer and biochemical reaction resistances; moreover, the variation in product and by-product distribution, specific substrate uptake rates, yield and maintenance coefficient were investigated in the pilot scale batch bioreactor at QO/VR = 0.5 vvm and agitation rates of N= 250, 500, 625, and 750 min-1, and dissolved oxygen levels DO= 20%, 40% conditions, while medium components were CGlucose= 8.0 kg m-3, C(NH4)2HPO4= 5.0 kg m-3 and salt solution at controlled pHc=7.2. The highest cell concentration and benzaldehyde lyase activity were obtained at DO=40% condition as 3.0 kg m-3 and A=1095 Ucm-3, respectively. v Then a mathematical model was proposed to estimate benzaldehyde lyase activity as function of time, agitation rate, cell concentration, dissolved oxygen concentration, and by-product concentration with reasonable accuracy.