Abstract: Growth and proliferation of bacteria may be inhibited in urine stored in a urine drainage container by placing urease in the container to generate sufficient ammonia to elevate the pH thereof to an alkaline level unfavorable for supporting microbial growth. Preferably, the urease is sealed in envelope means of semipermeable membrane which is capable of allowing diffusion of urea from urine stored in the container, while preventing substantial diffusion of the urease outwardly from the envelope means. Accordingly, the urease remains indefinitely reusable over many fillings and drainings of the container.