The pH dependent redox potential of the oxidoreductase glucose oxidase (GOx) from Aspergillus niger, which is the most frequently applied enzyme in electrochemical glucose biosensors and biofuel cells, was measured between pH 4.5 and 8.5 using UV/vis spectroelectrochemistry. In the entire pH range under investigation, the flavin adenine dinucleotide cofactor of GOx changed directly from the oxidized quinone to the doubly reduced hydroquinone. No stable semiquinoid species could be detected if electrochemical equilibrium was reached. From the pH dependency of the GOx redox potential, a pK(a) of 7.2 has been determined for the GOx flavohydroquinone. At pH values ≤6.0, a dependency of the reduction mechanism and the GOx redox potential on the presence of halides, especially on Cl(-), was observed. For the development of glucose biosensors and glucose biofuel cell anodes working at physiological or neutral pH, the GOx redox potentials at pH 7.4 and pH 7.0 are of main interest. Here values of E(1/2 pH 7.4) = -97 ± 3 mV and E(1/2 pH 7.0) = -80 ± 4 mV have been determined.

Drinking water production faces many different challenges with one of them being naturally produced cyanobacterial toxins. Since pollutants become more abundant and persistent today, conventional water treatment is often no longer sufficient to provide adequate removal. Among other emerging technologies, advanced oxidation processes (AOPs) have a great potential to appropriately tackle this issue. This review addresses the economic and health risks posed by cyanotoxins and discusses their removal from drinking water by AOPs. The current state of knowledge on AOPs and their application for cyanotoxin degradation is synthesized to provide an overview on available techniques and effects of water quality, toxin-and technique-specific parameters on their degradation efficacy. The different AOPs are compared based on their efficiency and applicability, considering economic, practical and environmental aspects and their potential to generate toxic disinfection byproducts. For future research, more relevant studies to include the degradation of less-explored cyanotoxins, toxin mixtures in actual surface water, assessment of residual toxicity and scale-up are recommended. Since actual surface water most likely contains more than just cyanotoxins, a multi-barrier approach consisting of a series of different physical, biological and chemical-especially oxidativetreatment steps is inevitable to ensure safe and high-quality drinking water.

Drinking water production faces many different challenges with one of them being naturally produced cyanobacterial toxins. Since pollutants become more abundant and persistent today, conventional water treatment is often no longer sufficient to provide adequate removal. Amongst other emerging technologies, advanced oxidation processes (AOPs) have a great potential to appropriately tackle this issue. This review addresses the economic and health risks posed by cyanotoxins and discusses their removal from drinking water by AOPs. The current state of knowledge on AOPs and their application for cyanotoxin degradation is synthesized to provide an overview on available techniques and effects of water quality, toxin- and technique-specific parameters on their degradation efficacy. The different AOPs are compared based on their efficiency and applicability, considering economic, practical and environmental aspects and their potential to generate toxic disinfection byproducts. For future research, more relevant studies to include the degradation of less explored cyanotoxins, toxin mixtures in actual surface water, assessment of residual toxicity and scale-up are recommended. Since actual surface water most likely contains more than just cyanotoxins, a multi-barrier approach consisting of a series of different physical, biological and chemical – especially oxidative – treatment steps is inevitable to ensure safe and high quality drinking water.

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