Mesophilic and thermophilic fermentation of activated sludge for volatile fatty acids production: focusing on anaerobic degradation of carbohydrate and protein.

The volatile fatty acids (VFAs) productions, as well as particulate organics decomposition, soluble chemical oxygen demand (SCOD) yield, and the VFAs production pathways from mesophilic and thermophilic anaerobic fermentation in waste activated sludge were investigated. Batch experiments showed that the decomposition rate of volatile suspended solids (VSS), particulate carbohydrate (P-C) and particulate protein (P-P) followed the first-order kinetic model at different temperatures. However, the intermediates, accumulated in the process of protein or carbohydrate digestion had a more significant inhibitory effect on the production of VFAs during the mesophilic anaerobic acidification process. The production of VFAs by thermophilic anaerobic fermentation is 2086.05 mg COD/L, which is about twice the production under mesophilic conditions. Among them, the concentration and proportion of high molecular weight organic acids such as isobutyric acid (320.29 mgCOD/L) and isovaleric acid (745.75 mgCOD/L) are relatively high. Then 13C stable isotope labelling experiment demonstrated that, the decomposition of carbohydrates yields 77% acetic acid and 86% butyric acid, while protein breakdown produces 85% propionic acid and 99% valeric acid. This confirms that carbohydrates are more favourable for the formation of even-carbon organic acids, while proteins tend to yield odd-carbon organic acids. Additionally, this helps refine the pathway for valeric acid formation during anaerobic acidogenesis.

Automated online optical biosensing system for continuous real-time determination of microcystin-LR with high sensitivity and specificity: early warning for cyanotoxin risk in drinking water sources.

The accelerated eutrophication of surface water sources and climate change have led to an annual occurrence of cyanobacterial blooms in many drinking water resources. To minimize the health risks to the public, cyanotoxin detection methods that are rapid, sensitive, real time, and high frequency must be established. In this study, an innovative automated online optical biosensing system (AOBS) was developed for the rapid detection and early warning of microcystin-LR (MC-LR), one of the most toxic cyanotoxins and most frequently detected in environmental water. In this system, the capturing molecular MC-LR-ovalbumin (MC-LR-OVA) was covalently immobilized onto a biochip surface. By an indirect competitive detection mode, samples containing different concentrations of MC-LR were premixed with a certain concentration of fluorescence-labeled anti-MC-LR-mAb, which binds to MC-LR with high specificity. Then, the sample mixture was pumped onto the biochip surface, and a higher concentration of MC-LR led to less fluorescence-labeled antibody bound onto the biochip surface and thus to lower fluorescence signal. The quantification of MC-LR ranges from 0.2 to 4 µg/L, with a detection limit determined as 0.09 µg/L. The high specificity and selectivity of the sensor were evaluated in terms of its response to a number of potentially interfering cyanotoxins. Potential interference of the environmental sample matrix was assessed by spiked samples, and the recovery of MC-LR ranged from 90 to 120% with relative standard deviation values <8%. The immunoassay performance of the AOBS was validated with respect to that of conventional high-performance liquid chromatography, and the correlation between methods agreed well (R(2) = 0.9762). This system has successfully been applied to long-term, continuous determination and early warning for MC-LR in Lake Tai from June 2011 to May 2012. Thus, the AOBS paves the way for a vital routine online analysis that satisfies the high demand for ensuring the safety of drinking water sources. The AOBS can also serve as early warning system for accidental or intentional water pollution.

Evanescent wave aptasensor for continuous and online aminoglycoside antibiotics detection based on target binding facilitated fluorescence quenching.

The biosensors capable for on-site continuous and online monitoring of pollutants in environment are highly desired due to their practical importance and convenience. The group specific detection of pollutants is especially attractive due to the diversity of environmental pollutants. Here we devise an evanescent wave aptasensor based on target binding facilitated fluorescence quenching (FQ-EWA) for the online continuous and group-specific detection of aminoglycoside antibiotics (AMGAs). In FQ-EWA, a fluorophore labeled DNA aptamer selected against kanamycin was used for both the target recognition in solution and signal transduction on optical fiber of EWA. The aptamers form multiple-strand complex (M-Apt) in the absence of AMGAs. The binding between AMGA and the aptamer disrupts M-Apt and leads to the formation of AMGA -aptamer complex (AMGA-Apt). The photo-induced electron transfer between the fluorophore and AMGA partially quenches the fluorescence of AMGA-Apt. The structure-selective absorption of AMGA-Apt over M-Apt on the graphene oxide further quenches the fluorescence of AMGA-Apt. Meanwhile, the unbound aptamers in solution assemble with the unlabeled aptamers immobilized on the fiber to form M-Apt. The amount of M-Apt on the fiber is inversely proportional to the concentration of AMGAs, enabling the signal-off detection of AMGAs from 200nM to 200µM with a detection limit of 26nM. The whole detection process is carried out in an online mode without any offline operation, providing a great benefit for system automation and miniaturization. FQ-EWA also shows great surface regeneration capability and enables the continuous detection more than 60 times.

TriPleX™ waveguide-based fluorescence biosensor for multichannel environmental contaminants detection.

In order to realize the multi-analyte assays for environmental contaminants, an optical biosensor utilizing laser-induced fluorescence-based detection via the binding of biomolecules to the surface of an integrated TriPleX™ waveguide chip on a glass substrate (fused silica, FS) is described. As far as we know, this is the first demonstration of using the TriPleX™ technology to fabricate the waveguide chip on a FS substrate. The sensor consists of 32 individually addressable sensor patches, which were formed on the chip surface by exploiting 3 Y-junction splitters, creating four equal rows of eight evanescently excited windows in parallel. The basic low-loss SiO2/Si3N4 TriPleX™ waveguide configuration in combination with on-chip spotsize convertors allows for both high fiber-to-chip coupling efficiency and enables at the same time individually optimized high chip surface intensity and low patch-to-patch deviation. Moreover, the complementary metal-oxide-semiconductor compatible fabrication of waveguide chip allows for its mass production at low cost. By taking MC-LR, 2,4-D, atrazine and BPA as the model analytes, the as-proposed waveguide based biosensor was proven sensitive with the detection limits of 0.22 µg/L for MC-LR, 1.18 µg/L for 2, 4-D, 0.2 µg/L for atrazine and 0.06 µg/L for BPA. Recoveries of the biosensor towards simultaneous detection of MC-LR, 2, 4-D, atrazine and BPA in spiked real water samples varied from 84% to 120%, indicating the satisfactory accuracy of the established technology.

Hydrophilic and antimicrobial core-shell nanoparticles containing guanidine groups for ultrafiltration membrane modification.

Physical blending is a common technique to improve the water flux and antifouling performance of ultrafiltration (UF) membranes. In the present work, a novel hydrophilic and antimicrobial core-shell nanoparticle was synthesized through the chemical grafting of poly(guanidine-hexamethylenediamine-PEI) (poly(GHPEI)) on the surface of silica nanoparticles (SNP). The synthesized core-shell nanoparticles, poly(GHPEI) functionalized silica nanoparticles (SNP@PG), were incorporated into polyethersulfone (PES) to fabricate hybrid UF membranes by a phase inversion process. The chemical composition, surface and cross section morphologies, hydrophilicity, water flux and protein rejection of the membranes were evaluated by a series of characterizations. Results show that the prepared PES/SNP@PG hybrid membrane exhibits not only improved water flux, which is around 2.6 times that of the pristine PES membrane, but also excellent resistance to organic fouling and biofouling.

Integrated optical waveguide-based fluorescent immunosensor for fast and sensitive detection of microcystin-LR in lakes: Optimization and Analysis.

Nowadays, biosensor technologies which can detect various contaminants in water quickly and cost-effectively are in great demand. Herein, we report an integrated channel waveguide-based fluorescent immunosensor with the ability to detect a maximum of 32 contaminants rapidly and simultaneously. In particular, we use waveguide tapers to improve the efficiency of excitation and collection of fluorescent signals in the presence of fluorophore photobleaching in a solid surface bioassay. Under the optimized waveguide geometry, this is the first demonstration of using such a type of waveguide immunosensor for the detection of microcystin-LR (MC-LR) in lake water. The waveguide chip was activated by (3-Mercaptopropyl) trimethoxysilane/N-(4-maleimidobutyryloxy) succinimide (MTS/GMBS) for immobilization of BSA-MC-LR conjugate, which was confirmed to have uniform monolayer distribution by atomic force microscopy. All real lake samples, even those containing MC-LR in the sub-microgram per liter range (e.g. 0.5 µg/L), could be determined by the immunosensor with recovery rates between 84% and 108%, confirming its application potential in the measurement of MC-LR in real water samples.

Highly sensitive and simultaneous detection of melamine and aflatoxin M1 in milk products by multiplexed planar waveguide fluorescence immunosensor (MPWFI).

Mycotoxins and industrial chemicals, such as aflatoxin M1 and melamine, now commonly exist in milk and cause potential health risks. This study presents an indirect competitive immunoassay through multiplex planar waveguide fluorescence immunosensor (MPWFI) for rapid, sensitive, and simultaneous detection and quantification of aflatoxin M1 and melamine by applying the principle of immunoreaction and total internal reflect fluorescent. Double-channel standard curves with appropriate logistic correlation (R(2)>0.99) were plotted, respectively. The working ranges (0.073-0.400 ng/mL and 26.38-270.00 ng/mL, respectively) were calculated, as well as the limit of detection (0.045 and 13.37 ng/mL, respectively), when two analytes were simultaneously detected. Both results satisfied the requirements for the maximum amount set by the WHO, which illustrated that the current method was better than some other standard methods. The recovery rates in the actual samples ranged from 85% to 103%, with relative standard deviations between 1.3% and 6.5%, which indicated high accuracy and repeatability.

Compact quantitative optic fiber-based immunoarray biosensor for rapid detection of small analytes.

Immunoarrays have been proven to be powerful tools for high-throughput analysis of multiple analytes. In this paper, a proof-of-concept development of a novel optic fiber-based immunoarray biosensor for the detection of multiple small analytes is presented. This was developed through immobilization of two kinds of hapten conjugates, MC-LR-OVA and NB-OVA, onto the same fiber optic probe. The technique is significantly different from conventional immunoarray sensors. Microcystin-LR (MC-LR) and trinitrotoluene (TNT) could be detected simultaneously and specifically within an analysis time of about 10 min for each assay cycle. The limits of detection for MC-LR and TNT were 0.04 µg/L and 0.09 mg/L, respectively. Good regeneration performance, binding properties, and robustness of the sensor surface of the proposed immunoarray biosensor ensure the cost-effective and accurate measurement of small analytes. The change in concentration of the hapten conjugates immobilized onto the sensor surface was also proven to have no significant effection on the performance of immunoarray sensor, which is essential to the application of the immunoarray in real samples detection. This compact and portable quantitative immunoarray provides an excellent multiple assay platform for clinical and environmental samples.

[Synthesis of complete antigen of microcystin-LR and its antibody production].

Based on the analysis of coupling location, coupling regent, carrying protein and coupling process, completed antigen of Microcystin-LR (MC-LR) was synthesized. A free amidogen was introduced to microcystin-LR (MC-LR) using chemical modification (aminoethylation) of its 7th core amino acids, N-methyl-dehydroalanine. The intermediate product Aminoethyl-MC-LR (H2N-etMC-LR) was purified by Solid Phase Elute (SPE) and identified by Mass Spectrometry, then coupled with BSA through glutaraldehyde to be complete antigen. The completed antigen was dialyzed and identified by SDS-PAGE, UV-scanning and bio-mass spectrometry. The result show that the coupling ratio between MC-LR and BSA of complete antigen in average was over 5, and it is sufficient to immunity.