Microwave sterilization in school microbiology

Abstract

For a long time the standard procedure for ensuring total sterilization of equipment and culture media for microbiological investigations has been to autoclave; this method destroys even the most resistant bacterial spores by a combination of heat and pressure, using steam (typically 120°C and 100 kPA for 15–20 minutes). Most biology teachers are familiar with the noise, smell, condensation, and time involved with the use of the autoclave. However, there is no other effective, efficient way of preparing class-size quantities of materials. Microbiology in both research and industry is a much wider and more important field than its coverage in many biology courses might suggest. There is now an increasing trend to incorporate more microbiology into the Biology and Science syllabuses, especially in relation to Biotechnology and areas such as Food Science. While autoclaving is likely to remain the recommended method of producing large amounts of sterile apparatus and media, a typical school situation could require the quick sterilization of relatively small quantities of materials. In such circumstances the autoclave is slow and uneconomical. The use of the microwave oven could provide a suitable alternative to the familiar autoclave or the pressure cooker. This article describes an investigation carried out in a school Biology department, using a domestic microwave oven, to compare the relative attributes of the autoclave and microwave oven in school use.