Steri vac 5xl

Sheridan^® PVC ETTs (Hudson RIC, Temecula, CA, USA) were modified using a fungal lipase produced from R. arrhizus (Sigma Aldrich, St Louis, MO, USA). PVC ETTs were cut into pieces with a length of 0.6 cm and a width of 0.3 cm. PVC pieces were then immersed in 20 mL of a 0.1% mass solution of R. arrhizus lipase dissolved in a 1M potassium phosphate buffer (Fisher Scientific, Waltham, MA, USA). These pieces were then gently agitated on an incubator shaker (Excella E24, New Brunswick Scientific, Edison, NJ, USA) for 24 hours at 37°C and 200 rpm. After 24 hours, the lipase solution was replaced and the ETT pieces were agitated for an additional 24 hours. At the end of 48 hours, the ETT pieces were removed from the lipase solution and were washed with distilled water. The ETT pieces were then sterilized using ethylene oxide exposure (Steri-Vac 5XL, 3M, Minneapolis, MN, USA) in a 16-hour sterilization cycle.
The activity of the R. arrhizus lipase used in this experiment was 10.5 U/g, where one unit is defined as the amount of enzyme that catalyzes the release of 1 μmol of oleic acid per minute at pH 7.4 and 40°C.20