Detection of Cyanobacteria in Eutrophic Water Using a Portable Electrocoagulator and NanoGene Assay

Selectively retaining nutrients in biochar in magnesium added two-zone staged copyrolysis of blue algae and corn gluten wastes

The disposal of blue algae (BA) and corn gluten (CG) wastes and the simultaneous recovery of abundant phosphorus (P) and nitrogen (N) by pyrolysis to obtain biochars with high fertility is a promising strategy. However, pyrolysis of BA or CG alone by a conventional reactor cannot reach the target. Herein, we propose a novel MgO-enhanced N and P recovery method by designing a two-zone staged pyrolysis reactor to highly efficiently recover N and P with easily available plant forms in BA and CG. The results show that a 94.58% total phosphorus (TP) retention rate was achieved by means of the special two-zone staged pyrolysis method, in which the effective P (Mg₂PO₄(OH) and R-NH-P) accounted for 52.9% of TP, while the total nitrogen (TN) reached 4.1 wt%. In this process, stable P was formed first at 400 °C to avoid rapid volatilization and then to form hydroxyl P at 800 °C. Meanwhile, Mg-BA char in the lower zone can efficiently absorb N-containing gas generated by the upper CG, forming dispersible N. This work is of great significance for improving the green utilization value of P and N in BA and CG.

Water quality shifts the dominant phytoplankton group from diatoms to dinoflagellates in the coastal ecosystem of the Bohai Bay

In this study, we conducted two cruises in the Bohai Bay (China) focusing on phytoplankton community and relation to water quality. The evaluation revealed that most of the open area was non-eutrophic, whereas the river inlet had severe eutrophication. Phytoplankton populations respond differently to different aquatic environments and are controlled by more than two factors, as revealed by aggregated boosted tree analysis. Notably, a shift in the phytoplankton community structure was observed during the seasonal transition, from the dominance of diatoms to the co-dominance of diatoms-dinoflagellates. However, the relative abundance of dinoflagellates increased by 14 % in autumn, when the harmful algae species Akashiwo sanguinea exclusively predominated; this was primarily linked to the nutrient ratios, temperature, and dissolved oxygen. The eutrophication and organic pollution had direct effects on phytoplankton abundance. Overall, our findings may provide further insights into the impacts of eutrophic environments on phytoplankton community structure in coastal systems.

Advances in bacterial concentration methods and their integration in portable detection platforms: A review

Early detection and identification of microbial contaminants is crucial in many sectors, including clinical diagnostics, food quality control and environmental monitoring. Biosensors have recently gained attention among other bacterial detection technologies due to their simplicity, rapid response, selectivity, and integration/miniaturization potential in portable microfluidic platforms. However, biosensors are limited to the analysis of small sample volumes, and pre-concentration steps are necessary to reach the low sensitivity levels of few bacteria per mL required in the analysis of real clinical, industrial or environmental samples. Many platforms already exist where bacterial detection and separation/accumulation systems are integrated in a single platform, but they have not been compiled and critically analysed. This review reports on most recent advances in bacterial concentration/detection platforms with emphasis on the concentration strategy. Systems based on five concentration strategies, i.e. centrifugation, filtration, magnetic separation, electric separation or acoustophoresis, are here presented and compared in terms of processed sample volume, concentration efficiency, concentration time, ability to work with different types of samples, and integration potential, among others. The critical evaluation presented in the review is envision to facilitate the development of future platforms for fast, sensitive and in situ bacterial detection in real sample.

Switchable inhibitory behavior of divalent magnesium ion in DNA hybridization-based gene quantification

Mg2+ ion is a switchable inhibitor that can cause either under or over-estimation at different concentrations in DNA hybridization based gene quantification.

Ozonation enhancement of low cost double-stranded DNA binding dye based fluorescence measurement of total bacterial load in water

We demonstrated the feasibility of using ozonation to enhance the performance of dsDNA binding dye SYBR Green I in the fluorescence measurement of total bacterial load in water. Unlike its membrane permeable but expensive equivalent such as SYTO82 dye, SYBR Green I is many times cheaper but membrane impermeable. Ozonation allowed SYBR Green I dye to permeate the membrane and bind with the dsDNA within by first breaching it. Using E. coli K12 bacteria at serial dilution ratios from 1/1 (980 CFU mL⁻¹) to 1/200, we achieved corresponding quantification from 618.7 ± 9.4 to 68.0 ± 1.9 RFU (100 to 11.00% normalized RFU). In comparison, plate counting and optical density measurement were only able to quantify up till a serial dilution ratio of 1/50 (40 CFU mL⁻¹ and 0.0421, respectively). Most importantly with ozonation, the sensitivity of SYBR Green I dye based fluorescence measurement was improved by ∼140 to 210% as compared to that without ozonation. Given its low electrical power consumption, lab-on-chip compatibility and reagent-less nature, ozonation is highly compatible with portable fluorimeters to realize low-cost monitoring of total bacterial load in water.

Principle of ozonation enhanced dsDNA binding dye based fluorescence measurement of total bacterial load in water.

A simple reagent-less approach using electrical discharge as a substitution for chelating agent in addressing genomic assay inhibition by divalent cations

Electrical discharge treatment was shown to be a viable substitution for chelating agent in genomic assays. Divalent cation Mg2+ inhibits the performance of DNA hybridization based genomic assays by binding to the DNA and disrupting DNA hybridization. Until now, chelating agents such as ethylenediaminetetraacetic acid (EDTA) was the only option to address the presence of Mg2+ in samples. However, EDTA is a well-known environmental contaminant. In this work, we successfully employed electrical discharge instead of EDTA to render Mg2+ insipid. Its preliminary efficacy was first observed via circular dichroism (CD) and zeta potential analyses. After electrical discharge treatment, the reduction in CD shift at 280 nm was significant for samples with 10-3 and 10-8 M Mg2+. The zeta potential of Mg2+ laden samples were also restored from -4.71 ± 1.38 to -20.59 ± 6.37 mV after electrical discharge treatment. Both CD shift and change in zeta potential suggested that 2 min of electrical discharge treatment could prevent Mg2+ from binding to DNA. The complete efficacy of electrical discharge treatment was demonstrated with the performance recovery (within ∼15% of the control) of a genomic assay variant (NanoGene assay) while analyzing Mg2+ laden samples (10-5-10-3 M). Assuming 10 million samples are analyzed annually, the proposed electrical discharge treatment (∼50 mW per sample) would allow us to trade environmental contamination by ∼50 kg of hazardous EDTA with a single 250 W STC (standard test conditions) solar panel.

A molecular-based method to estimate the risk associated with cyanotoxins and odor compounds in drinking water sources

A biomolecular-based monitoring approach for the assessment of water quality hazards and risks associated with cyanobacteria was developed and validated in drinking reservoirs in Taiwan and the Philippines. The approach was based upon the measurement of gene abundances of toxigenic Microcystis and Cylindrospermopsis; for cyanotoxins; and for aesthetically offensive earthy-musty odor compounds. This was compared to conventional monitoring approaches, which included cell enumeration by microscopy, and toxin and odor compound analysis by instrumental analytical methods and immunoassays as appropriate for the metabolites. The validation involved samples from ten major reservoirs on Taiwan's main island, nineteen reservoirs on the offshore islands, and Laguna de Bay in the Philippines. The gene-based approach was successfully validated statistically and compared to conventional widely utilized risk assessment schemes which have employed 'Alert Levels' for toxic cyanobacteria. In this case a new integrated scheme of 'Response Levels' is proposed which incorporates odor metabolite hazards in addition to cyanotoxins and is based upon gene copy numbers to derive quantitative triggers. The comprehensive scheme evaluated from these locations is considered to be more precise and efficient for both monitoring and as a risk assessment diagnostic tool, given that it offers the capacity for analysis of the abundance of genes for cyanobacterial metabolites in large numbers of natural water samples in a significantly reduced period of time compared to the approaches of cell enumeration by microscopy or metabolite analytical techniques. This approach is the first time both the hazard and risk for both odors and cyanotoxins from cyanobacteria have been considered together in a monitoring scheme and offers an improved means for determining the Response Levels in the risk assessment process for cyanobacteria and their metabolites in drinking water sources.

The Implications of Fragmented Genomic DNA Size Range on the Hybridization Efficiency in NanoGene Assay

DNA hybridization-based assays are well known for their ability to detect and quantify specific bacteria. Assays that employ DNA hybridization include a NanoGene assay, fluorescence in situ hybridization, and microarrays. Involved in DNA hybridization, fragmentation of genomic DNA (gDNA) is necessary to increase the accessibility of the probe DNA to the target gDNA. However, there has been no thorough and systematic characterization of different fragmented gDNA sizes and their effects on hybridization efficiency. An optimum fragmented size range of gDNA for the NanoGene assay is hypothesized in this study. Bacterial gDNA is fragmented via sonication into different size ranges prior to the NanoGene assay. The optimum size range of gDNA is determined via the comparison of respective hybridization efficiencies (in the form of quantification capabilities). Different incubation durations are also investigated. Finally, the quantification capability of the fragmented (at optimum size range) and unfragmented gDNA is compared.