Green phytoextracts as natural photosensitizers in LED-based photodynamic disinfection of multidrug-resistant bacteria in wastewater effluent

• Published in: Chemosphere (Oxford) Vol. 297; p. 134157
• Main Authors: Sarker, M.A. Rashid, Ahn, Young-Ho
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.06.2022
• Subjects: Antibacterial assessment; Disinfection - methods; Escherichia coli; Gram-Negative Bacteria; Multidrug-resistant bacteria; Municipal wastewater; Photodynamic disinfection; Photosensitizing Agents - chemistry; Photosensitizing Agents - pharmacology; Phytoextracts; Reactive Oxygen Species - pharmacology; Waste Water; Photodynamic disinfection; Antibacterial assessment; Multidrug-resistant bacteria; Municipal wastewater; Phytoextracts
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2022.134157

The photodynamic treatment (PDT) process is a promising technology to control emerging pollutants and antimicrobial resistance problems in the water environment. The reactive oxygen species (ROS) produced when natural and nontoxic photosensitizers (PS) are exposed to light are the key functional components of the PDT process that can effectively achieve microbial inactivation with minimal negative impact. This study examined the application of green phytoextracts from two plants, Chamaecyparis obtusa and Moringa oleifera, as natural photosensitizers for the white light-emitting diode (LED) based photodynamic disinfection of multidrug-resistant (MDR) and total coliforms (TC) from secondary effluent in full-scale municipal wastewater treatment plants. Gas chromatography–mass spectrometry and Fourier transform infrared spectroscopy showed that the phytoextracts contained 57 compounds, particularly aromatic and phenolic hydroxyl compounds. The phytoextracts showed an excellent activity as a PS compared to the intrinsic antibacterial effect. Under a light intensity of 17 mW/cm2, the complete inactivation (6.55 Log CFU/mL) was observed at an irradiation time of 100 min for Escherichia coli ART-2 and 80 min for Staphylococcus aureus, meaning that E. coli was resistant. The light intensity was an important factor influencing photodynamic disinfection. For the complete disinfection of TC satisfying the water reclamation regulation, the irradiation time requirement was 20 min under a light intensity of 80 mW/cm2. During the photodynamic reaction, a significant amount of ROS was generated from the phytoextracts as the light irradiation time was increased. The major ROS was singlet oxygen (1O2, Type II) during the initial 40 min of reaction time and hydroxyl radical (•OH, Type I) after 40 min until complete inactivation. [Display omitted] •Two green phytoextracts applied as antibacterial agents and natural photosensitizers.•Natural photosensitizers were very active in photodynamic disinfection.•High-strength MDR and total coliform bacteria were inactivated successfully.•Complete TC disinfection from WW effluent satisfied the water reclamation rule.•Both types of ROS (1O2 and .•OH) contributed to the photodynamic disinfection.