Probing the intracellular organic matters released from the photocatalytic inactivation of bacteria using fractionation procedure and excitation-emission-matrix fluorescence

Abstract

Photocatalysis provides a "green" and effective strategy for water disinfection. During the photocatalytic disinfection process, intracellular organic matter (IOM) from bacterial cells may be released into the bulk solution. In this study, the role of released IOM in the photocatalytic bacterial inactivation was investigated by fractionation procedure and fluorescence excitation-emission-matrix (EEM) combined with parallel factor analysis (PARAFAC) approaches. The normal bacterial cells treated by TiO-UVA in the presence and absence with fractionated IOM results implied that the released IOM would be either absorbed on the surface of the photocatalysts or reacted by the photo-generated reactive species, and thereby affecting the kinetics of photocatalytic bacterial inactivation. Fluorescence EEM-PARAFAC results showed that two components (C1 and C3) associated with tryptophan- and tyrosine-like proteins were released. While another two components (C2 and C4) were the oxidation products, and their intensities were found to negatively correlate with those of C1 and C3, respectively. Microtox test results indicated that toxicity occurred during the photocatalytic bacterial inactivation process. The toxicity was found to decrease after the bacteria were completely inactivated, and completely removed if provided a sufficient reaction time. Of particular interest is that a significant high linear correlation was observed between the toxicity and the maximum fluorescence intensity of C4. The results and information obtained in this study will be important for further developing photocatalysis in water/wastewater disinfection.

Activation of persulfates by natural magnetic pyrrhotite for water disinfection: Efficiency, mechanisms, and stability

“…For instance, a number of biohazards are naturally resistant to UV and chlorination (Eischeid et al, 2011;Rizzo et al, 2013a, b); the toxic and corrosive characteristics of ozone limit its practical application (Anastasi et al, 2013); the formation of disinfection byproducts (DBPs) by chlorination and ozonation are with potential carcinogenicity or toxicity (Parker et al, 2014;Sharma et al, 2014). Therefore, effectively removing biohazards from water is a challenge that has received great attention (Sun et al, 2014;Huang et al, 2017), and versatile new technologies are highly needed to simultaneously inactivate biohazards and eliminate disinfection debris.…”

Two‐dimensional nanomaterials for photocatalytic water disinfection: recent progress and future challenges

“…This is because in comparison with organics, microorganisms are more sensitive to the composition of reaction media and the nature of catalysts in photocatalytic oxidation . Characteristics of the water matrix, such as ionic strength, oxygen, pH value, humic acid concentration, or even intracellular organic matter released from bacteria inactivation, etc., are of direct relevance to antibacterial efficiency by influencing the RS generation process and surface contact between cells and photocatalysts.…”

“…A triplet of excited states of HA in light is responsible for the phenomenon, as extra ROS of •OH, 1 O 2 and H 2 O 2 could be produced . It is of interest to notice that organic matter and cell debris resulting from photocatalytic microbial inactivation have a feedback impact on the disinfection process . Similar to HA in water, the organics and debris can consume the photogenerated RSs and adsorb on the photocatalyst surface, which decelerates the kinetics of disinfection.…”

Challenges in quantifying and characterizing dissolved organic carbon: Sampling, isolation, storage, and analysis

“…Microbials may secrete soluble microbial products into the water continuum under environmental stress, such as acidification and biocides (Wang & Zhang, 2010). Moreover, acidification and biocides could lead to destruction of the cell wall structure and subsequently to a release of dissolved cytoplasmic organic substances (Huang et al., 2017). These substances will affect the characterization of natural DOC and should be taken into consideration.…”