| Popis: |
Cryptosporidium in wastewater presents a major public health concern for water safety. However, bactericidal efficiencies of Cryptosporidium oocysts using conventional disinfection methods are still hampered due to the resistance produced by their thick outer wall. In this study, we present a novel UV inactivation with significantly enhanced efficiency by trypsin pretreatment. Notably, the inactivation performance (log-reduction) of oocysts was 73.75-294.72% higher than that obtained in individual UV irradiation under identical conditions. Experimental observations and supporting mechanistic analyses suggest that the trypsin can cleave proteins layer on oocyst wall, which facilitates UV irradiation to penetrate into the oocysts and attack their genomic DNA (gDNA). The trypsin displayed considerable operational stability in the reaction mixture, and its dissociation effect of oocyst wall was indicated by the fact that 64.50% of oocysts displayed early apoptosis after trypsinization. The combined treatment almost totally destroyed the oocysts coat and deformed their shape according to scanning electron microscopy. This resulted in the release of cellular proteins and gDNA, and their concentrations in bulk solution increased by 1.22–8.60 times. As UV irradiation time was prolonged, gDNA was degraded into small fragments with lower molecular weight. Both the laddering and diffuse smear patterns in the gel indicated significant detrimental effect on gDNA and viability of oocysts. Overall, this study demonstrates the enhanced UV inactivation of Cryptosporidium oocysts by trypsin and provides the underlying mechanisms for the process. |
