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The increasing occurrence of toxic cyanobacterial blooms worldwide represents a critical health and environmental risk. Catalytic wet peroxide oxidation (CWPO) has emerged as an efficient and environmentally friendly technology for the removal of cyanotoxins in water. Nevertheless, its effectiveness has just been demonstrated in deionized water or simple synthetic aqueous matrices. In this work, the effect of the different components of the aqueous matrix on the CWPO of cyanotoxins was deeply evaluated considering the widespread properties of the Iberian Peninsula freshwaters. The presence of Cl-, HCO 3 - and SO 4 2- ions reduced the oxidation rate of cylindrospermopsin (CYN) up to 70–80% at the highest concentrations tested (2000, 250 and 500 mg L−1 for Cl-, HCO 3 - and SO 4 2-, respectively) due to their hydroxyl radical scavenging capacity. The presence of natural organic matter (NOM) resulted in a similar outcome (oxidation rate reduction up to 90% at the highest concentration tested, 20 mg L−1), but in this case due to the consumption of hydroxyl radicals in competition with CYN oxidation. The presence of NO 3 - and H 2 PO 4 - did not show any significant effect on CYN oxidation. Similarly, the presence of cyanobacteria (Chrysosporum ovalisporum , 50 µg chlorophyll-a L−1) did not appreciably affect the CYN oxidation rate. These results were consistent with those obtained by evaluating the impact of real aqueous matrices from drinking water treatment plants (DWTPs) located in Castilla y León and Extremadura regions (Spain) on CWPO performance. This knowledge is key to the implementation of the technology for the treatment of surface waters affected by toxic cyanobacterial blooms. [Display omitted] [ABSTRACT FROM AUTHOR]

Cyanotoxins are secondary metabolites produced by cyanobacteria, of varied chemical nature and toxic effects. Although cyanobacteria thrive in all kinds of ecosystems on Earth even under very harsh conditions, current knowledge on cyanotoxin distribution is almost restricted to freshwaters from temperate latitudes. In this review, we bring to the forefront the presence of cyanotoxins in extreme environments. Cyanotoxins have been reported especially in polar deserts (both from the Arctic and Antarctica) and alkaline lakes, but also in hot deserts, hypersaline environments, and hot springs. Cyanotoxins detected in these ecosystems include neurotoxins-anatoxin-a, anatoxin-a (S), paralytic shellfish toxins, β-methylaminopropionic acid, N-(2-aminoethyl) glycine and 2,4-diaminobutyric acid- and hepatotoxins -cylindrospermopsins, microcystins and nodularins-with microcystins being the most frequently reported. Toxin production there has been linked to at least eleven cyanobacterial genera yet only three of these (Arthrospira, Synechococcus and Oscillatoria) have been confirmed as producers in culture. Beyond a comprehensive analysis of cyanotoxin presence in each of the extreme environments, this review also identifies the main knowledge gaps to overcome (e.g., scarcity of isolates and -omics data, among others) toward an initial assessment of ecological and human health risks in these amazing ecosystems developing at the very edge of life. [ABSTRACT FROM AUTHOR]

Abstract: The growth rates, production and release of the potent cytotoxin cylindrospermopsin (CYN) were studied in batch and semi-continuous cultures of Aphanizomenon ovalisporum (Cyanobacteria; Nostocaceae) strains UAM 289 and UAM 290 from Spain, over a gradient of temperatures (10–40°C) and irradiances (15–340μEm−2 s−1). This species grew in temperatures ranging from 15°C to 35°C as well as under all irradiances assayed. The growth rates ranged from 0.08d−1 to 0.35d−1, and the maximum growth was recorded above 30°C and at 60μEm−2 s−1. CYN was produced under all conditions where net growth occurred. Total CYN reached up to 6.4μgmg−1 dry weight, 2.4μgmm−3 biovolume, 190.6fgcell−1 and 0.5μgμg−1 chlorophyll a. Although CYN concentrations varied only 1.9-fold within the 15–30°C range, a drastic 25-fold decrease was observed at 35°C. The irradiance induced up to 4-fold variations, with maximum total CYN measured at 60μEm−2 s−1. An elevated extracellular CYN share ranging from 20% to 35% was observed during the exponential growth phase in most experiments, with extreme temperatures (15 and 35°C) being related to the highest release (63% and 58%, respectively) and without remarkable influence of irradiance. Growth did not have a direct influence on either CYN production or release throughout the entire range of experimental conditions. Our study demonstrates a strong and stable production and release of CYN by A. ovalisporum along field-realistic gradients of temperature and light, thus becoming a predictive tool useful for the management of water bodies potentially affected by this ecologically plastic cyanobacterium. [Copyright &y& Elsevier]

Abstract: Biodegradation of cylindrospermopsin produced by Aphanizomenon ovalisporum UAM 290 was studied. In the 40-day degradation experiment conducted, bacterial communities from two waterbodies with and without previous exposure to the toxin were used. Further, and in order to study the potential effect of other organic substrates on the degradation of cylindrospermopsin, three different sources of cylindrospermopsin were used: toxic extracts obtained by methanolic extraction and by ultrasonication in water with 5% formic acid and 0.9% NaCl and toxin naturally present in the spent media of an Aphanizomenon ovalisporum culture. Despite active growth of the bacterial population and consumption of DOC in presence of the toxic extracts, no degradation of cylindrospermopsin could be observed during the 40-day period. Considering that cylindrospermopsin is abundant in the extracellular fraction and that photodegradation in the field seems to be limited, a lack of efficient biodegradation as observed in our study could be of greatest importance and further explain the accumulation of this toxin in the dissolved fraction of the waterbodies investigated. [Copyright &y& Elsevier]

The development of cost-efficient and environmentally friendly technologies for the removal of cyanotoxins from water is crucial, given the increasingly frequent appearance of toxic cyanobacterial blooms. In this work, the application of catalytic wet peroxide oxidation (CWPO) promoted by natural magnetite for the removal of the highly toxic cyanotoxin cylindrospermopsin (CYN) has been investigated. A fixed-bed reactor packed with magnetite powder and granules was used to treat a continuous flow of CYN-bearing water. Experiments were carried out under ambient conditions and circumneutral pH (pH0 = 5). The effect of the main variables of the process, viz. magnetite load (8–14 g), feed flow rate (0.1–0.25 mL min−1), H2O2 dose (0.5–8 mg L−1) and initial CYN concentration (25–100 μg L−1), were systematically analyzed. CYN conversion values and kinetic constants were calculated to evaluate the feasibility of the catalytic system. The process was highly effective in the removal of the cyanotoxin, achieving up to 80% CYN conversion under optimized conditions (flow rate = 0.2 mL min−1, [H2O2]0 = 5 mg L−1, WFe3O4 = 14 g, pH0 = 5, T = 25 °C). It also showed reasonable activity (~55% CYN conversion) in two real samples (pond and river water). The decay on CYN conversion in these cases was mainly due to the scavenging of hydroxyl radicals by the co-existing species present in the matrices. Remarkably, the catalytic system showed high stability with limited iron leaching (the iron leached at the end of the experiments represented less than 0.2 wt.% of the catalyst's initial iron content) in all cases. Its stability was further confirmed in a long-term continuous experiment (60 h time on stream). Furthermore, the magnetite granules at the top layer of the packed bed avoided the loss of magnetite powder from the reactor, confirming the suitability of the system for continuous long-term application. [ABSTRACT FROM AUTHOR]

The occurrence of harmful cyanobacterial blooms has unabated increased over the last few decades, posing a significant risk for public health. In this work, we investigate the feasibility of catalytic wet peroxide oxidation (CWPO) promoted by modified natural magnetite (Fe 3 O 4 -R400/H 2 O 2), as an inexpensive, simple-operation and environmentally-friendly process for the removal of the cyanotoxins that show the major impact on drinking water: microcystins (MC-LR and MC-RR), cylindrospermopsin (CYN), anatoxin- a (ATX) and saxitoxin (STX). The performance of the system was evaluated under ambient conditions and circumneutral pH (pH 0 = 5) using relevant cyanotoxin concentrations (100–500 μg L−1). The nature of the cyanotoxins determined their reactivity towards CWPO, which decreased in the following order: MC-RR > CYN > MC-LR ≫ ATX > STX. In this sense, microcystins and CYN were completely removed in short reaction times (1–1.5 h) with a low catalyst concentration (0.2 g L−1) and the stoichiometric amount of H 2 O 2 (2–2.6 mg L−1), while only 60–80% conversion was achieved with ATX and STX in 5 h. In these cases, an intensification of the operating conditions (1 g L−1 catalyst and up to 30 mg H 2 O 2 L−1) was required to remove both toxins in 1 h. The impact of the main components of freshwaters i.e. natural organic matter (NOM) and several inorganic ions (HCO 3 −, HPO 4 2-, SO 4 2-) on the performance of the process was also investigated. Although the former led to a partial inhibition of the reaction due to HO· scavenging and catalyst coating, the latter did not show any remarkably effect, and the versatility of the process was finally confirmed in a real surface water. To further demonstrate the effectiveness of the catalytic system, the toxicity of both the initial cyanotoxins and the resulting CWPO effluents was measured with the brine shrimp Artemia salina. Remarkably, all CWPO effluents were non-toxic at the end of the treatment. Image 1 • The catalytic system Fe 3 O 4 -R400/H 2 O 2 is effective for the removal of cyanotoxins. • The reactivity of cyanotoxins decreased in the order: MC-RR > CYN > MC-LR ≫ ATX > STX. • The versatility of the process was demonstrated in different water matrices. • Oxidation effluents were non-toxic to the brine shrimp Artemia salina. [ABSTRACT FROM AUTHOR]