Phosphate and nitrate supplementations to evaluate the effect on cell biomass, intra and extracellular nodularin and nodulopeptin 901 produced by the cyanobacterium Nodularia spumigena KAC 66.

Blooms of the cyanobacterium Nodularia spumigena occur regularly in the Baltic Sea typically producing a wide range of bioactive peptides including the hepatotoxin nodularin (NOD), spumigins, anabaenopeptins and nodulopeptins (molecular weights: 917, 901 and 899Da). This study reports the production of intracellular and extracellular NOD and nodulopeptin 901 (the major secondary metabolites), at various nitrate and phosphorus concentrations produced by N. spumigena KAC 66 which had been originally isolated from the Baltic Sea. The growth was observed by cell biomass and intracellular and extracellular peptides monitored by high-performance liquid chromatography with photodiode array and mass spectrometry (HPLC-PDA-MS). In the present work, it was found that high concentrations of nitrate and phosphorus have a considerable effect on biomass and toxin levels of N. spumigena. In common with many studies, the maximum amount of NOD was retained within the cells during 5weeks of growth. In contrast, as much as ~ 40% of nodulopeptin 901 was excreted into the medium throughout the duration of experiments. At 6.5 and 3.5mgL−1 nitrate, the maximum concentrations of peptide per unit biomass was 1.78ng NOD (in week 4) and 1.42ngnodulopeptin 901 μg−1 (in week 3) were detected. However, the high concentrations of both peptides were produced in the absence of nitrate. The phosphate experiment indicated growth, and peptide production was dependent on availability of phosphorus. At 0mgL−1 of phosphate, an increased amount of intracellular (502.4ngμg−1 biomass) nodulopeptin 901 was recorded. This report evaluates the effect of nutrients on the production of biomass and toxins, which may predict the formation and control of blooms of N. spumigena in the Baltic Sea. It also provides information to improve the growth conditions to produce high biomass and toxins under suitable conditions, which may be helpful in the research. The results from the current study will also be helpful to predict about possible blooms of N. spumigena in the Baltic Sea with reference to increase or decrease in nitrate and phosphate concentrations

Degradation of okadaic acid in seawater by UV/TiO2 photocatalysis: proof of concept.

The consumption of contaminated shellfish with marine toxins causes adverse socioeconomical, environmental and health impacts. The marine toxin okadaic acid (OA) provokes diarrhetic shellfish poisoning (DSP) syndrome characterized by severe gastrointestinal symptoms. Therefore, there is increasing interest in removing these toxins from the marine environment to protect shellfish harvesting sites. Photocatalysis is proposed as an efficient method to detoxify the marine environment. In this study, Prorocentrum lima was used to produce high purity DSP toxins, in particular OA, for degradation studies. The profiling, characterization and quantification of DSP toxins in the culture of P. lima were achieved by ultrahigh performance liquid chromatography coupled to quadrupole-time of flight mass spectrometry (UPLC-QTOF-MSE) for accurate-mass full spectrum acquisition data. The effectiveness of UV/TiO2 system to degrade OA in seawater was assessed in lab-scale experiments and identification of transformation products was proposed based on the data obtained during analysis by UPLC-QTOF-MSE. The detoxification potential of the UV/TiO2 system was investigated using the phosphatase inhibition assay. Sufficient amount of high-purity OA (25 mg, >90% purity) was produced in-house for use in photocatalysis experiments by simple reversed-phase flash chromatography. Complete degradation of OA was observed in seawater after 30 min and 7.5 min in deionized water. The rate constants fitted with the pseudo-first order kinetic model (R2>0.96). High-resolution mass spectrometry analysis of the photocatalyzed OA allowed tentative identification of four transformation products. Detoxification was achieved in parallel with the degradation of OA in deionized water and artificial ocean water (≤ 20 min) but not for seawater. Overall, results suggest that UV/TiO2 photocatalysis can be an effective approach for degrading OA and their TPs in the marine environment. To the best of our knowledge, this is the first report on the use of photocatalysis to degrade marine toxins and its promising potential to protect shellfish harvesting sites

A comparison of the effectiveness of TiO2 photocatalysis and UVA photolysis for the destruction of three pathogenic micro-organisms.

TiO2 photocatalysis has demonstrated efficacy as a treatment process for water contaminated with chemical pollutants. When exposed to UVA light TiO2 also demonstrates an effective bactericidal activity. The mechanism of this process has been reported to involve attack by valence band generated hydroxyl radicals. In this study when three common bacterial pathogens, Escherichia coli, Salmonella enterica serovar Enteritidis and Pseudomonas aeruginosa, were exposed to TiO2 and UVA light a substantial decrease in bacterial numbers was observed. Control experiments in which all three pathogens were exposed to UVA light only resulted in a similar reduction in bacterial numbers. Moreover, exposure to UVA light alone resulted in the production of a smaller than average colony phenotype among the surviving bacteria, for all three pathogens examined, a finding which was not observed following treatment with UVA and TiO2. Small slow growing colonies have been described for several pathogenic bacteria and are referred to as small colony variants. Several studies have demonstrated an association between small colony variants and persistent, recurrent and antibiotic resistant infections. We propose that the production of small colony variants of pathogenic bacteria following UVA treatment of drinking water may represent a health hazard. As these small colony variants were not observed with the UVA/TiO2 system this potential hazard is not a risk when using this technology. It would also appear that the bactericidal mechanism is different with the UVA/TiO2 process compared to when UVA light is used alone

Destruction of cyanobacterial toxins by semiconductor photocatalysis.

The rapid destruction of microcystin, a cyanobacterial toxin, using a titanium dioxide photocatalyst is observed; the process is extremely efficient with high concentrations of toxin completely undetectable within 10-40 min, depending on the initial concentration

Rapid analytical methods for the microalgal and cyanobacterial biorefinery: application on strains of industrial importance.

To realise the potential of microalgae in the biorefinery context, exploitation of multiple products is necessary for profitability and for bioproduct valorisation. Appropriate analytical tools are required for growth optimisation, culture monitoring and quality control purposes, with safe, low-tech and low-cost solutions favourable. Rapid, high-throughput and user-friendly methodologies were devised for a) determination phycobiliproteins, chlorophylls, carotenoids, proteins, carbohydrates and lipids and b) qualitative and quantitative carotenoid profiling using UPLC-PDA-MSE. The complimentary methods were applied on 11 commercially important microalgal strains including Prasinophytes, Haptophytes and cyanobacteria, highlighting the suitability of some strains for coproduct exploitation and the methods utility for research and industrial biotechnology applications. The UPLC method allowed separation of 41 different carotenoid compounds in < 15 minutes. Simple techniques are described for further quantification and comparison of pigment profiles, allowing for easy strain selection and optimisation for pigment production, with suitability for biotechnological or biomedical applications

A study of the kinetic solvent isotope effect on the destruction of microcystin-LR and geosmin using TiO2 photocatalysis.

We have previously reported the effectiveness of TiO2 photocatalysis in the destruction of species generated by cyanobacteria, specifically geosmin and microcystin-LR. In this paper we report an investigation of factors which influence the rate of the toxin destruction at the catalyst surface. A primary kinetic solvent isotope effect of approximately 1.5 was observed when the destruction was performed in a heavy water solvent. This is in contrast to previous reports of a solvent isotope effect of approximately 3, however, these studies were undertaken with a different photocatalyst material. The solvent isotope effect therefore appears to be dependent on the photocatalyst material used. The results of the study support the theory that the photocatalytic decomposition occurs on the catalyst surface rather than in the bulk of the solution. Furthermore it appears that the rate determining step is not oxygen reduction as previously reported

High value phycotoxins from the dinoflagellate Prorocentrum.

Marine dinoflagellates produce chemically diverse compounds, with a wide range of biological activity (antimicrobial, anticancer, treatment of neurodegenerative disease along with use as biomedical research tools). Chemical diversity is highlighted by their production of molecules such as the saxitoxin family of alkaloids (C10H17N7O4 - 299 g/mol) to the amphipathic maitotoxin (C164H256O68S2Na2 - 3,422 g/mol), representing one of the largest and most complex secondary metabolites characterised. Dinoflagellates, are most well-known for the production of red tides which are frequently toxic, including okadaic acid and related dinophysistoxins, which are tumour promoters. The mode of action for these phycotoxins, is by specific inhibition of protein phosphatases, enzymes essential in regulation of many cellular processes. Hence, these compounds are being used for vital cell regulation studies. However, the availability of useful amounts of these compounds has restricted research. Chemical synthesis of some compounds such as okadaic acid has been investigated, but the complexity of the molecule resulted in many lengthy steps and achieved only a poor yield. The use of naturally occurring phytoplankton has been investigated as a potential source of these compounds, but it has been shown to be unreliable and impractical. The most practical option is large scale culture with down-stream processing/purification which requires specialist facilities and expertise. This review, describes the biotechnological potential of these organisms and the challenges to achieve useful yields of high quality phycotoxins using Prorocentrum spp. as an example to produce okadaic acid

Water taste and odor (T&O): challenges, gaps and solutions from a perspective of the WaterTOP network.

Aesthetic aspects of drinking water, such as Taste and Odor (T&O), have significant effects on consumer perceptions and acceptability. Solving unpleasant water T&O episodes in water supplies is challenging, since it requires expertise and know-how in diagnosis, evaluation of impacts and implementation of control measures. We present gaps, challenges and perspectives to advance water T&O science and technology, by identifying key areas in sensory and chemical analysis, risk assessment and water treatment, as articulated by WaterTOP (COST Action CA18225), an interdisciplinary European and international network of researchers, experts, and stakeholders

Processes influencing the destruction of microcystin-LR by TiO2 photocatalysis.

We have previously reported the effectiveness of TiO2 photocatalysis in the destruction of the cyanotoxin microcystin-LR [P.K.J. Robertson, L.A. Lawton, B. Münch, J. Rouzade, J. Chem. Soc., Chem. Commun., 4 (1997) 393; P.K.J. Robertson, L.A. Lawton, B. Münch, B.J.P.A. Cornish, J. Adv. Oxid. Technol., in press]. In this paper we report an investigation of factors which influence the rate of the toxin destruction at the catalyst surface. A primary kinetic isotope effect of approximately 3 was observed when the destruction was performed in a heavy water solvent. Hydroxylated compounds were observed as products of the destruction process. No destruction was observed when the process was investigated under a nitrogen atmosphere