Date of Award
Master of Science in Chemical Engineering - (M.S.)
Chemical Engineering, Chemistry and Environmental Science
Richard Clyde Parker
A total of thirty chemostat runs were evaluated for steady state biomass concentration of L. brevis and arginine deiminase activity at dilution rates ranging from 0.022 to 0.1.07 h-1 for a substrate feed consisting of 1.0% glucose and 0.5% arginine (w/v). Biomass concentration and enzyme activity responses were also evaluated for variations in glucose concentration from 0.05% to 1.5% and variations in arginine concentrations from 0.25% to 1.0% at a constant dilution rate (0.06 h-1).
The system exhibited multiple steady states for the range of dilution rates from 0.022 to 0.107 h-1. A steady state biomass concentration of 0.131 mg cells/ml and an enzyme activity measuring 0.065 units/mg p were obtained at a low dilution rate (0.036 h-1). At a higher dilution rate (0.097 h-1) the biomass was 0.049 mg cells/mi and the enzyme activity was 0.022 units/mg p. Wash-out of biomass occurred above a dilution rate of 0.107 h-1.
Optimum enzyme activity in the chemostat occurred when the glucose concentration was reduced to 0.05% with an arginine concentration of 0.5%. Batch results demonstrated an even higher activity for a stationary phase culture with the same initial substrate concentrations. The resulting optimum activities for chemostat and batch cultures were 0.083 and 0.114 units/mg p, respectively.
The possibilities of glucose-mediated catabolite repression or other mechanisms regulating arginine catabolism are discussed for both batch and continuous conditions.
Carque, Jeanette, "The catabolism of arginine by lactobacillus brevis in a chemostat" (1985). Theses. 2051.