Supercritical Fluid CO2 Technique for Destruction of Pathogenic Fungal Spores in Solid Clinical Wastes

The present study deals with the inactivation of fungal spores in clinical waste using the advanced supercritical carbon-dioxide (SC-CO2) treatment technique. The process of inactivation was investigated under different conditions of pressure, temperature, and processing time. The efficiency of SC-CO2 was determined in terms of log reduction and inactivation rate of fungal spores. Almost 100% inactivation of initial fungal spores was obtained. Predicted and experimental log reduction of fungal spores was found to be 5.93 and 6.00, respectively, under optimal conditions (35MPa, 75 degrees C in 90min). SC-CO2 treated Aspergillus niger and Penicillium simplicissimum spores were examined using scanning electron microscopy which showed spore damage in the form of rupture, tear, and shape distortion. These damages confirmed complete spore inactivation when no renewed fungal growth occurred after the treated samples were cultured onto fresh media. The inactivation of fungal spores using SC-CO2 and autoclave inhibits the production of lipase, cellulase, amylase, and protease enzymes. Thus, without addition of any chemicals, the SC-CO2 sterilization method can be potentially used for the inactivation of microorganisms in clinical waste as well as in food and pharmaceutical products.