ACETAMIDE DEGRADATION BY A CONTINUOUS-FED BATCH CULTURE OF BACILLUS-SPHAERICUS

The methanogenesis of acetamide occurs through a two-step reaction in methanogenic sludges. First, acetamide is hydrolyzed to acetate and am monia by a strict aerobic bacterium (Bacillus sphaericus), then acetat e is used by Bacillus as carbon source or converted to methane by meth anogens. In this work, the kinetics of acetamide degradation by B. sph aericus was studied in a continuous reactor with biomass accumulation, fed with acetamide. The oxygen supplied was dissolved in the feed (6. 4 mg/L) to resemble conditions in an anaerobic wastewater treatment re actor. A reaction in series model (acetamide --> acetate --> biomass) was used to find the kinetic parameters. Results show that B. sphaeric us can hydrolyze acetamide in a second-order reaction with K-1 = 1.1 L /g/d, implying that the amount of biomass determines the rate and that no reaction will take place at specific loading rates greater than 35 gAm/gX/d. Growth parameters on acetate, as carbon source, under limit ing O-2 conditions, are mu(max) = 0.102/d, K-s = 37 mg/L, Y = 0.081 gX /gAm.