Exposure of Microcystis aeruginosa to Hydrogen Peroxide under Light: Kinetic Modeling of Cell Rupture and Simultaneous Microcystin Degradation

Abstract

The effect of hydrogen peroxide on the cell integrity of a cyanobacterium, Microcystis aeruginosa, and on the release and degradation of microcystins (MCs) under simulated sunlight was investigated. The cyanobacterium was exposed to H2O2 in the range of 0-60 mg·L(-1) for 3.5 h. Production of OH radical in the solution was estimated by a chemical probe method. More than 99% (2 log) of the M. aeruginosa cells were ruptured or damaged by 3 h for all the treatments. Loss of cell integrity over time revealed two distinct phases. Cells retained their integrity during the initial lag phase and rapidly ruptured following first-order reaction afterward. A linear relationship was found between the duration of the lag phase and the steady-state concentration of OH radical. Release of MCs was closely correlated with the loss of cell integrity. Sequential reaction models were developed to simulate the release and degradation of MCs. These models were able to quantitatively describe the kinetics of all reactions under different H2O2 doses and extended exposure time. In particular, the models successfully predicted the concentration change of MCs using independently measured parameters. These models provide a simple and quantitative means to estimate the interaction of oxidants and cells and the consequent release of metabolites during oxidation treatment of cyanobacterium-laden waters.

Existing and emerging cyanocidal compounds: new perspectives for cyanobacterial bloom mitigation

“…the sum of particulate and water soluble fractions, rapidly decreased by more than 90 % in \3 days (Matthijs et al 2012). The latter observations on rapid MC degradation are supported by reports on microbial degradation of MC (Lawton et al 2011;Dziga et al 2013) and hydroxyl radical catalysed processing of microcystin (Huo et al 2015).…”

“…This hypothesis was thereafter successfully tested in the laboratory (Dráb-ková et al 2007a, b;Weenink et al 2015) and in the field (Matthijs et al 2012). The actual cyanobacteria killing compound may very well be not HP itself but a compound derived from HP, for which hydroxyl radical formation by UV light and catalysed by Fenton reaction active ions has been presented as a candidate by Huo et al (2015).…”

Impacts of Hydrogen Peroxide and Copper Sulfate on the Control of Microcystis aeruginosa and MC-LR and the Inhibition of MC-LR Degrading Bacterium Bacillus sp.

“…This kind of inhibition followed by regrowth of cyanobacteria during the application of H 2 O 2 has been reported by Qian et al (2010) [62], where M. aeruginosa grew after 96 h of exposure to a dose of 100 µM (3.4 mg·L −1 ) H 2 O 2 . In addition, Huo et al, (2015) [54] reported a two-stage in M. aeruginosa cell integrity change when exposed to H 2 O 2 under light illumination, with cell rupturing following the Delayed Chick−Watson Model, where before the lag time all cells remained integrated and after the lag time the cells started to be ruptured. Although the experiments in that study were only conducted for 6 h, much less than in the current work, their results demonstrated that Microcystis cells are not resistant to H 2 O 2 exposure with 99% of the Microcystis cells damaged within 3 h when exposed to 22.34 W·m −2 (solar irradiance at the surface of the water).…”

“…The present study shows that under the condition of light intensity = 2.3 W·m −2 and H 2 O 2 dose = 20 mg·L −1 , degradation of H 2 O 2 was three times faster in the sample with M. aeruginosa (2.3 × 10 6 cells/mL) than that in deionized water (Figure 1). Huo et al (2015) [54] [57] reported a general copper dose ranging from 0.025 to 1 mg·L −1 that can be used to achieve control of algae blooms. With lower copper sulfate doses, although slight inhibition was observed if compared with controlled samples, cells still grew within 14 days of the experiments (Figure 2a).…”

Microcystin-LR Biodegradation by Bacillus sp.: Reaction Rates and Possible Genes Involved in the Degradation

“…Understanding the quality of these waters is therefore an important issue to safeguard public health. Cyanobacteria are an important group of microorganisms present in lakes and reservoirs, and some produce toxins [1,2] and taste and odor compounds [3,4]. Microcystins (MCs) [cyclo-(D-Ala1-X2-D-MeAsp3-Z4-Adda5-D-Glu6-Mdha7)], a group of heptapeptide hepatotoxins, are produced by several cyanobacteria genus, such as Microcystis, Anabaena, Nostoc, and Planktothrix [5], and they are toxic to animals and humans [6,7].…”