title: Optimizing supercritical carbon dioxide in the inactivation of bacteria in clinical solid waste by using response surface methodology.
abstract: Clinical solid waste (CSW) poses a challenge to health care facilities because of the presence of pathogenic microorganisms, leading to concerns in the effective sterilization of the CSW for safe handling and elimination of infectious disease transmission. In the present study, supercritical carbon dioxide (SC-CO2) was applied to inactivate gram-positive Staphylococcus aureus, Enterococcus faecalis, Bacillus subtilis, and gram-negative Escherichia coli in CSW. The effects of SC-CO2 sterilization parameters such as pressure, temperature, and time were investigated and optimized by response surface methodology (RSM). Results showed that the data were adequately fitted into the second-order polynomial model. The linear quadratic terms and interaction between pressure and temperature had significant effects on the inactivation of S. aureus, E. coli, E. faecalis, and B. subtilis in CSW. Optimum conditions for the complete inactivation of bacteria within the experimental range of the studied variables were 20 MPa, 60 °C, and 60 min. The SC-CO2-treated bacterial cells, observed under a scanning electron microscope, showed morphological changes, including cell breakage and dislodged cell walls, which could have caused the inactivation. This espouses the inference that SC-CO2 exerts strong inactivating effects on the bacteria present in CSW, and has the potential to be used in CSW management for the safe handling and recycling-reuse of CSW materials.
authors: Department of Environmental Technology, School of Industrial Technology, Universiti Sains Malaysia, 11800 Penang, Malaysia.
authors: Md Sohrab
authors: MS
authors: Hossain
authors: School of Distance Education, Universiti Sains Malaysia, 11800 Penang, Malaysia.
authors: Nik Norulaini
authors: NN
authors: Nik Ab Rahman
authors: Institute for Research in Molecular Medicine, Universiti Sains Malaysia, 11800 Penang, Malaysia.
authors: Venugopal
authors: V
authors: Balakrishnan
authors: Department of Environmental Technology, School of Industrial Technology, Universiti Sains Malaysia, 11800 Penang, Malaysia.
authors: Abbas F M
authors: AF
authors: Alkarkhi
authors: School of Dental Science, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia.
authors: Zainul
authors: Z
authors: Ahmad Rajion
authors: Department of Environmental Technology, School of Industrial Technology, Universiti Sains Malaysia, 11800 Penang, Malaysia. Electronic address: akmomar@usm.my.
authors: Mohd Omar
authors: MO
authors: Ab Kadir
mesh_terms: D001419:Bacteria / Q000187:drug effects* / Q000302:isolation & purification; D002245:Carbon Dioxide / Q000737:chemistry*; D008296:Malaysia; D017744:Medical Waste Disposal / Q000379:methods*; D050296:Microbial Viability / Q000187:drug effects*; D011312:Pressure; D013242:Sterilization / Q000379:methods*; D013696:Temperature; D013997:Time Factors
chemical_list: D017744:Medical Waste Disposal; D002245:Carbon Dioxide
keywords: Bacterial inactivation; Clinical solid waste; Optimization; Response surface methodology; Sterilization; Supercritical carbon dioxide