1•Sterilization–Why sterilize–The sterilization bioreaction–Effect of scaling on sterilization–MethodsWhy Sterilize?•Sterility – NO living organisms–Economic penalty is high for loss of sterility–Contamination–Vaccines must have only killed viruses–Recombinant DNA fermentations - exit streams must be sterilized
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2Sterilization Agents•Thermal - preferred for economic large-scale sterilizations of liquids and equipment•Chemical - preferred for heat-sensitive equipment–ethylene oxide (gas) for equipment–70% ethanol-water (pH 2) for equipment/surfaces–3% sodium hypochlorite for equipment•Radiation - UV for surfaces, x-rays for liquids (cost/safety)•Filtration–membrane filters have uniform micropores–depth filters of glass woolThermal Sterilization•Heat susceptibility is organism dependent.–Decimal reduction time (D Time) - Time to kill 90 % or 1 log unit of a population at a given temperature.•Moist heat - Acts by denaturationand coagulation of proteins.–To kill vegetative bacteria, yeast and mold -- 80º C for 5 -10 minutes; Mold spores -- 80º C for 30 minutes; Bacterial spores --121º C, 15 lbs/sq. in. pressure for at least 15 minutes.