Series Of Optimization Experiments Research Articles

Sustainable production of organic acids from chitin biomass catalyzed by Keggin-type heteropolyacid under hydrothermal condition

The “shell biorefinery,” which valorizes the shell waste chitin into fine chemicals, has developed rapidly in recent years. Herein, we present a novel base-free heteropolyacid-catalyzed oxidation method for the transformation of chitin biomass into organic acid. After a series of optimization experiments, a 5.93 % yield of formic acid and 25.09 % yield of acetic acid were achieved in the presence of 0.5 equivalent of Mo-V-P heteropolyacids (H4PMo11VO40·2H2O) and air at 180 °C under hydrothermal conditions for 4 h. Meanwhile, we have demonstrated that the Keggin-type heteropolyacid catalysts are capable of efficiently converting microcrystalline chitin into organic acids. The synthesized heteropolyacids are well characterized with FT-IR, XRD, ICP-AES, and TGA. The possible reaction pathway was speculated accordingly. This method offers several advantages, including readily available raw materials, simple operation, and relatively higher yield.

Adaptive control of transportation infrastructure in an urban environment using a real-coded genetic algorithm

The management of urban areas requires the development of an effective strategy for the evolution of transportation infrastructure to ensure the smooth flow of traffic and pedestrians. A crucial component of this infrastructure is the traffic light system, which plays a vital role in traffic control and traffic safety. Improving the efficiency of traffic control systems in intelligent transportation systems (ITS) has a significant impact on a city’s economy. As a result, the cost of fuel for road users can be reduced, and their level of social comfort can be improved, among other benefits. This paper proposes a novel approach to optimizing traffic flows in smart cities, based on the combined use of the genetic optimization algorithm and the ITS simulation model we developed. The proposed method aims to enhance the efficiency of existing traffic control systems and achieve optimal traffic flow patterns, thereby contributing to a more sustainable and efficient urban environment. The optimization algorithm shown here aggregates the objective functions using a simulation model of a real region of the Moscow road network. The model includes intersections, pedestrian crossings and other features that are implemented in the AnyLogic system. The research aims to create a decision-support system for managing urban transport infrastructure. This system will be used to optimize the duration of traffic light phases in order to minimize the time vehicles spend passing through key nodes in the urban road network. It will also optimize pedestrian flow, reducing the impact of traffic on the environment and improving fuel efficiency. By applying this approach, the capacity of the street network can be significantly increased. Additionally, the negative effects of traffic flow on the environment can be reduced by optimizing fuel use and reducing waiting times at intersections managed by traffic lights. The research methodology involves the development of a hybrid evolutionary search algorithm, the creation of a simulation model for transportation and pedestrian flows in the AnyLogic and a series of optimization experiments that demonstrate the effectiveness of the proposed approach when applied to the modeling of complex urban transportation systems.

Dibutylamide hydrophobic deep eutectic solvent used for selective extraction of Au(III) from hydrochloric acid medium

The effective and environmentally friendly recovery of gold from secondary resources has recently received increased attention. Hydrophobic deep eutectic solvent (HDES) composed of N,N-di-butylacetamide and 1-decanoic acid was used to construct the liquid-liquid extraction system to extract Au(III) from HCl medium. At first, DSC, TGA, FT-IR, and 1H NMR were used to describe the evidence of internal hydrogen bond interaction. The above evidence was verified in the molecular dynamics study of HDES. Then, a series of optimization experiments were carried out to investigate the extraction behaviors of HDES. Based on the results of optimization experiments, response surface method was used to explore the best experimental conditions and the results showed that HDES extracted 99% Au(III) under 0.56 mol/L HCl, 2.19 mol/L NaCl, and 5.83 mmol/L Au(III), and the maximum loading reached 77.0 mg/g. Further studies on the kinetics and thermodynamics of the extraction were used to propose an ion association mechanism. In addition, using 0.1 mol/L thiourea as the stripping agent, HDES displayed outstanding Au(III) selectivity and maintained the extraction efficiency in tests which involved 5-cycles. Overall, this study provides a green and efficient Au(III) recovery strategy for secondary resources.

Covalent organic framework with extraordinary intrinsic catalytic activity for electrochemical sensing of iodide ions

Environmental conservation and food safety have aroused enormous concerns owing to their close relationship with human health. Iodide ion (I−) could result in serious diseases in mankind. Thus, it is challenging and essential to develop an effective approach to capture and detect I−. Herein, the TT-COF(Zn) material prepared using 2,3,6,7-tetra (4-formyl phenyl) tetrathiafulvalene (TTF) and 5,10,15,20-tetrakis(para-aminophenyl) porphyrin Zinc (II) (TPZ) as building blocks were designed directly as electrode modified material for electrochemical sensing of I−. Combining the meritsofTPZ and TTF to construct the intrinsic efficient electron-transfer pathways, as well as the advantages of porous channel and single-site catalysis of COF, TT-COF(Zn) material-modified electrode showed excellent electrocatalytic performance towards the redox reaction of I−, which makes it a sensitive sensing platform for the electrochemical quantification of I−. After a series of optimization experiments, the I− sensor demonstrated a wide linear range (0.02–15 mM), low detection limit (3.15 μM), as well as other good sensing features. The proposed sensor also performed well in the determination of I− in real river samples. This work not only offers a simple method to assay I− effectively but also paves a way for the strategical design and synthesis of COFs for electrochemical sensing applications.

Multi-Objective optimization of solar park design under climatic uncertainty

The scarcity of land near energy demand poses the challenge of designing multi-functional solar parks in terms of land use in some countries. This requires solutions accounting for multiple conflicting objectives, e.g., power generation and multi-functional use of the land (agricultural, construction, ecological). Moreover, the performance of solar park projects in terms of these criteria is subject to uncertainties, e.g., meteorological aspects impacted by climate change, electricity prices, grid infrastructure availability.In this work we present a framework for multi-objective optimization under uncertainty to aid in the development of smart solar park configurations accounting for multi-purpose land use. A solar park simulator and a techno-economic model are combined to evaluate key performance indicators serving as objective functions. Meteorological uncertainty throughout the park lifetime is characterized through an ensemble of scenarios generated based on the variability of historical data, instead of the current practice of assessing the performance of solar park using a deterministic profile of an average meteorological year.The developed workflow is demonstrated through a case study where power yield and agricultural land use are two conflicting objectives being optimized with the orientation, tilt angle, spacing and height of the modules as the optimization variables. A series of optimization experiments with varying importance weights between the objectives is performed. Obtained solutions show solar park designs which double the available farming area without compromising the levelized cost of energy. These results showcase the value generated through an integrated framework for multi-objective optimization under uncertainty leading to optimized solar parks.

Experimental investigation of mid-spatial frequency surface textures on fused silica after computer numerical control bonnet polishing

Automated bonnet polishing is achieved using computer numerical control (CNC) technology. However, owing to specific toolpaths, CNC bonnet polishing is generally accompanied by the mid-spatial frequency (MSF) of surface textures on polished surfaces that could produce surface ripples or waviness and degrade image quality. In this study, the MSF surface textures on fused silica are investigated by developing a CNC bonnet polishing technique using a cerium oxide-filled polyurethane pad (LP66)—a cellular polyurethane material designed to handle high flatness and surface finishing requirements for optical glass materials. To minimize the MSF, optimal combinations of various polishing parameters, including tool offset, head speed, track spacing, and surface feed rate, are studied. Experimental results demonstrate that the head speed and feed rate significantly affect the surface texture during bonnet polishing. Although the tool offset does not cause surface textures, the material removal rate is affected. A series of optimization experiments is conducted, consequently leading to the effective removal of irregular surface ripples and a reduction of MSF errors. By optimizing the polishing parameters, extremely accurate surface quality is achieved, along with a root mean square error of 1.6 nm. These results demonstrate the potential applications of LP66 in CNC bonnet polishing for highly accurate freeform optical components.

Optimal design and experimental verification of high-temperature and high-pressure assembly of neutron diffraction based on PE-type press

High-pressure and high-temperature(high-P-T) <i>in-situ</i> neutron diffraction detection method is a field of growing interest, in particular, for its numerous applications in the field of condensed matter physics, crystal chemistry, geophysics, materials science and engineering. In this work, we design and optimize a set of assembly for high-P-T <i>in-situ</i> neutron diffraction experiment in neutron source of China by using Paris-Edinburgh(PE)-type press. The high-P-T experiment is carried out with a high-pressure neutron diffraction spectrometer (Phoenix) of China Mianyang Research Reactor (CMRR). A 1500 KN uniaxial loading system and a 1500 W constant current source provides extreme conditions of high-P-T for PE press. The toroidal anvil we use is made of tungsten carbide. We use two types of gaskets: one is machined from the null-scattering TiZr alloy and the other is made from the thermal insulation ceramic material of ZrO<sub>2</sub>. High-temperature furnace is formed by graphite. First, a simplified simulation analyses of the pressure change rates in different areas of the entire assembly are carried out, and it is concluded that the gasket I, II, III areas are designed with a gradient decreasing method. The compression ratio of the sample chamber is significantly improved. Then when the gasket reaches the same compression ratio, the cell pressure will be higher than the pressure before optimization. After that, we conduct experimental verification on the optimized design. Through a series of optimization experiments for assembly on the rheological control of gasket, the improvement of thermal insulation performance and the maximization of effective sample volume under high-P-T, the key technical indicators and design scheme of the high-P-T <i>in-situ</i> neutron diffraction platform are verified. The temperature and pressure in the sample cavity are calibrated by using the MgO's high-P-T <i>in-situ</i> neutron diffraction spectrum and equation of state. The <i>in-situ</i> neutron diffraction sample cavity environment of the designed platform can reach the conditions of 11.4 GPa and 1773 K. The successful development of this assembly greatly improves the experimental conditions of CMRR high-P-T neutron diffraction platform. At the same time, it has important reference significance for further improving the high-P-T loading conditions of the PE-type press and expanding the application scope of the PE-type press.

Specific detection and differentiation of classic goose parvovirus and novel goose parvovirus by TaqMan real-time PCR assay, coupled with host specificity

BackgroundClassic goose parvovirus (cGPV) causes high mortality and morbidity in goslings and Muscovy ducklings. Novel GPV (N-GPV) causes short beak and dwarfism syndrome (SBDS) in Cherry Valley ducks, Pekin ducks and Mule ducks. Both cGPV and N-GPV have relatively strict host specificity, with obvious differences in pathogenicity. Specific detection of cGPV and N-GPV may result in false positives due to high nucleotide similarity with Muscovy duck parvovirus (MDPV). The aim of this study was to develop a highly specific, sensitive, and reliable TaqMan real-time PCR (TaqMan qPCR) assay for facilitating the molecular detection of cGPV and N-GPV.ResultsAfter genetic comparison, the specific conserved region (located on the NS gene) of cGPV and N-GPV was selected for primer and probe design. The selected regions were significantly different from MDPV. Through a series of optimization experiments, the limit of detection was 50.2 copies/μl. The assay was highly specific for the detection of cGPV and N-GPV and no cross-reactivity was observed with E. coli., P.M., R.A., S.S., MDPV, N-MDPV, DAdV-A, DEV, GHPV, DHAV-1, DHAV-3, ATmV, AIV, MDRV and N-DRV. The assay was reproducible with an intra-assay and inter-assay variability of less than 2.37%. Combined with host specificity, the developed TaqMan qPCR can be used for cGPV and N-GPV in differential diagnoses. The frequency of cGPV in Muscovy duckling and goslings was determined to be 12 to 44%, while N-GPV frequency in Mule ducks and Cherry Valley ducks was 36 to 56%. Additionally, fluorescence-positive signals can be found in Mule duck embryos and newly hatched Mule ducklings. These findings provide evidence of possible vertical transmission of N-GPV from breeding Mule ducks to ducklings.ConclusionsWe established a quantitative platform for epidemiological investigations and pathogenesis studies of cGPV and N-GPV DNA that was highly sensitive, specific, and reproducible. N-GPV and cGPV infections can be distinguished based on host specificity.

A duplex PCR assay for the simultaneous detection and differentiation of Muscovy duck parvovirus and goose parvovirus

Both Muscovy duck parvovirus (MDPV) and goose parvovirus (GPV) can cause high mortality and morbidity in Muscovy ducklings. MDPVs and GPVs share high nucleotide identity, which can cause errors during differential diagnosis. In this study, the NS genes of both MDPVs and GPVs were chosen for the design of specific primers after genetic comparison. Only three primers (GF1, MF1 and MGR1) were designed for the duplex PCR assay: GF1 is specific for GPV only; MF1 is specific for MDPV only; and MGR1 is highly conserved for both MDPV and GPV. After a series of optimization experiments, the duplex PCR assay amplified a 161-bp fragment specifically for GPV, a 1197-bp fragment specifically for MDPV, and two fragments (161-bp and 1197-bp) for both GPV and MDPV. The lowest detection limit was 103 copies/μl. No amplification was obtained using nucleic acids from other pathogens (including DAdV-A, DuCV, DEV, GHPV, R.A., E. coli., P.M. and S.S.) occurring in Muscovy ducks. Application of the duplex PCR assay in field samples showed that even one-day-old Muscovy ducklings were both MDPV-positive and GPV-positive. In conclusion, a duplex PCR assay for the simultaneous detection and differentiation of MDPV and GPV was established using only three highly specific primers. Our finding suggested that country-wide vaccination with MDPV and GPV vaccines in waterfowls are necessary.

Cohort-friendly protocol for the determination of two urinary biomarkers of exposure to pyrethroids and neonicotinoids using gas chromatography-triple quadrupole mass spectrometry.

Neonicotinoids (NEOs) and synthetic pyrethroids (PYRs) are active ingredients of commercial pesticides and/or insecticides with extensive indoor and outdoor applications, worldwide. Improved exposure metrics are warranted for NEOs and PYRs, if we are to better understand their human health effects. A cohort-friendly protocol for determining non-specific biomarkers of exposure to NEOs and PYRs, e.g. 6-chloronicotinic acid (6-CN) and 3-phenoxybenzoic acid (3-PBA), respectively, in human urine voids was proposed. A series of optimization experiments were conducted to validate the bioanalytical protocol using gas chromatography coupled with triple quadrupole mass spectrometry (GC-QqQ-MS/MS) in MRM mode. The method reached low detection limits for both analytes (0.075μgL-1 for 6-CN and 0.050μgL-1 for 3-PBA) in a short preparation and analysis time. The method used small initial urine sample volume (2mL), short extraction time (≈ 240min for the batches of 32 samples) and instrumental analysis time (≈ 14min) for both pesticide metabolites in a single run. This protocol could facilitate the assessment of population exposure metrics for these pesticides and their inclusion in health risk assessment. Graphical abstract.

Fe-Nanoporous Carbon Derived from MIL-53(Fe): A Heterogeneous Catalyst for Mineralization of Organic Pollutants.

Catalytic electrodes were prepared via carbonization of MIL-53(Fe) on the surface of porous carbon felt electrodes (CF) for use in wastewater treatment by the heterogeneous electro-Fenton (EF) process. The best results were obtained when the carbon felt was pretreated with nitric acid, enhancing the affinity of the MIL-53(Fe) for the surface. Following a series of optimization experiments, carbonization conditions of 800 °C for 5 h were used to form Fe-nanoporous carbon (MOFs@CF). The as-prepared electrodes were used as both cathode and heterogeneous catalyst in the EF process for the mineralization of exemplar dye Acid Orange 7 (AO7). Total organic carbon (TOC) removal of 46.1% was obtained within 8 h of electrolysis at around neutral pH (6.5) and the electrode retained over 80% of its original efficiency over five treatment cycles.

High-density tungsten fabricated by selective laser melting: Densification, microstructure, mechanical and thermal performance

High-density pure tungsten (W) fabricated by selective laser melting (SLM) has been considered as a substantial challenge due to its high melting point of 3410 °C. In this study, near fully dense W samples with a relative density of 98.71% were obtained for the first time through a series of optimization experiments during the SLM process. The characteristics of the surface and the formation mechanism of the micro defects were systematically elucidated. Additionally, it was found that the typical microstructures of horizontal and vertical planes experienced successive changes, where coarser columnar grains changed to uniform finer grains when increasing the laser scan speed from 50 mm/s to 400 mm/s. The compressive strength, micro hardness and thermal conductivity of the optimal SLM sample was improved to 1523 MPa, 428 HV3 and 148 W/m·K, which were superior to the sample produced by the conventional methods. The relationship of processing parameters to the surface morphology and microstructure evolution and material properties associated with fusion reactors was established in order to optimize the performance of SLM pure W and explore the possibility of further application in fusion reactors.

Optimization of experimental conditions for whole oil gas-chromatography—An example of tight oil in Jimsar sag, Junggar Basin

A series of optimization experiments were conducted on programed temperature rates, injection mode and the inlet temperature to explore an optimum whole oil gas-chromatography experimental method for the tight oil in Jimsar sag, Junggar Basin. The results showed that the quality and quantity of the gas-chromatography fingerprint peaks were significantly improved by setting the programed temperature rate at 3–5 °C/min; splitting injection at a certain split ratio; setting the inlet temperature at 350 °C; increasing the oven temperature to 370 °C.

Novel sensor platform for rapid detection and quantification of coliforms on food contact surfaces

In this paper, a novel sensor platform based on screen printed carbon electrode coated by graphene modified polyacrylamide gel (GR/PAAGC) was developed and implemented for sampling, detection and enumeration of coliform bacteria (coliforms) on food contact surfaces. The optimized formula of polyacrylamide (PAA) and agar-agar increased the adhesive properties of the gel, being crucial for the coliforms recovery, attached to food contact surfaces. The 6-Chloro-3-indoxyl-β-D-galactopyranoside (6-CIGP) was used as a new electrochemical reporter for β-D-galactosidase activity. The released 6,6′-Dichloro-Indigo (6-DI) was directly detected by GR/PAAGC sensor. The presence of Isopropyl-β-D-thiogalactopyranoside (IPTG) and n-Octyl-β-D-thiogalactopyranoside (OBDG) in the gel contributed to reduction of the detection time. The addition of graphene enhanced the voltammetric signal and increased the conductivity of PAA gel. The anodic and cathodic peaks of the released product were directly proportional to the concentration of coliforms. Bacterial cell concentrations ranging from 1.6log10CFU/mL to 6.6log10CFU/mL were detected. Well-shaped, sharp voltammetric curves were generated within 3 h. Redox peaks exhibited good sensitivity with detection limits (LOD) < 0.6log10CFU/mL. After series of optimization experiments, coliforms ranging from 0.6log10CFU/cm2 to 6.610CFU/cm2 on stainless steel surfaces have been detected within 30 min with a LOD of 0.1log10CFU/cm2. The developed rapid, sensitive, reproducible and specific sensor successfully applied for single detection as well as for real-time monitoring of growth of coliform bacteria on stainless steel surfaces during food processing.

Ultrasensitive Detection of Protein Based on Graphene Quantum Dots with Resonance Light Scattering Technique.

In this paper, a simple, label-free and ultrasensitive resonance light scattering (RLS) method for ultratrace protein detection was investigated using graphene quantum dots (GQDs) as probes. Due to the electrostatic interaction between GQDs and protein, the RLS intensity was gradually enhanced as the protein was added into the GQDs solution. Through a series of optimization experiments, the optimal detection conditions of the GQDs solution were as follows: pH = 7.4, 2 M ion concentration and 60 μM GQDs. Under the optimized conditions, the linear correlation between the GQDs and the concentration of protein was observed from 10 μM to 60 μM with the correlation coefficient (R2) of 0.9978, and the limit of detection (LOD) was 2.4 μM. Time-resolved fluorescence spectrum showed that the electron transition channel was not affected by the protein self-assembled on the surface of GQDs, which indicated that the interaction between GQDs and protein was mainly the electrostatic interaction. The proposed method revealed that the RLS enhancement effect from the self-assembled GQDs-protein hybrid nano-system provided a green and simple method to establish ultrasensitive biosensors.

New ELISA-based method for the detection of O-GlcNAc transferase activity in vitro

ABSTRACTO-GlcNAcylation is a dynamic, reversible, post-translational modification that regulates many cellular processes. O-GlcNAc transferase (OGT) is the sole enzyme transferring N-acetylglucosamine from uridine diphosphate (UDP)-GlcNAc to selected serine/threonine residues of cytoplasm and nucleus proteins. Aberrant of OGT activity is associated with several diseases, suggesting OGT as a novel therapeutic target. In this study, we created a new enzyme linked immunosorbent assays (ELISA)-based method for detection of OGT activity. First, casein kinase II (CKII), a well-known OGT substrate, was coated onto ELISA plate. Second, the GlcNAc transferred by OGT from UDP-GlcNAc to CKII was detected using an antibody to O-GlcNAc and then the horseradish peroxidase (HRP)-labeled secondary antibody. At last, 3,3′,5,5′-tetramethylbenzidine (TMB), the substrate of HRP, was used to detect the O-GlcNAcylation level of CKII which reflected the activity of OGT. Based on a series of optimization experiments, the RL2 antibody was selected for O-GlcNAc detection and the concentrations of CKII, OGT, and UDP-GlcNAc were determined in this study. ST045849, a commercial OGT inhibitor, was used to verify the functionality of the system. Altogether, this study showed a method that could be applied to detect OGT activity and screen OGT inhibitors.

The Optimization and Characterization of an RNA-Cleaving Fluorogenic DNAzyme Probe for MDA-MB-231 Cell Detection.

Breast cancer is one of the most frequently diagnosed cancers in females worldwide and lacks specific biomarkers for early detection. In a previous study, we obtained a selective RNA-cleaving Fluorogenic DNAzyme (RFD) probe against MDA-MB-231 cells, typical breast cancer cells, through the systematic evolution of ligands by exponential process (SELEX). To improve the performance of this probe for actual application, we carried out a series of optimization experiments on the pH value of a reaction buffer, the type and concentration of cofactor ions, and sequence minimization. The length of the active domain of the probe reduced to 25 nt from 40 nt after optimization, which was synthesized more easily and economically. The detection limit of the optimized assay system was 2000 MDA-MB-231 cells in 30 min, which is more sensitive than the previous one (almost 5000 cells). The DNAzyme probe was also capable of distinguishing MDA-MB-231 cell specifically from 3 normal cells and 10 other tumor cells. This probe with high sensitivity, selectivity, and economic efficiency enhances the feasibility for further clinical application in breast cancer diagnosis. Herein, we developed an optimization system to produce a general strategy to establish an easy-to-use DNAzyme-based assay for other targets.

Precision machining of high aspect-ratio rotational part with wire electro discharge machining

Precision and micro rotational parts are widely used in various industries, such as micro probes for medical instruments, contact pins for micro assembly applications, micro electrodes for micro Electrical discharge machining (μ-EDM) or micro Electro-chemical discharge machining (μ-ECDM). In this research, a uniform annular area layer by layer feeding strategy was proposed to fabricate high aspect ratio, small radii rotational components on a conventional Wire electrical discharge machining (WEDM) machine equipped with an auxiliary spindle. The uniform annular area layer by layer feeding strategy consisted of the roughing and finishing stages. First, the theoretical Material removal rate (MRR) and radial infeed rate for each layer were determined for the roughing stage, and the theoretical surface roughness, Rz in the finishing stage was researched. Then, a series of optimization experiments were conducted to investigate the influence of the parameters on MRR and the machined surface roughness. A group of pin electrodes were machined by applying this feed strategy with the optimized parameters, and the minimum diameter of the pin electrodes was 40 μm with an aspect-ratio of 60. Finally, micro electrodes for an injection nozzle were achieved with this novel process and a qualified injection nozzle for powder metallurgy was fabricated with the machined micro electrodes.

Synergistic fusion of vertical graphene nanosheets and carbon nanotubes for high-performance supercapacitor electrodes.

Graphene and carbon nanotubes (CNTs) are attractive electrode materials for supercapacitors. However, challenges such as the substrate-limited growth of CNTs, nanotube bundling in liquid electrolytes, under-utilized basal planes, and stacking of graphene sheets have so far impeded their widespread application. Here we present a hybrid structure formed by the direct growth of CNTs onto vertical graphene nanosheets (VGNS). VGNS are fabricated by a green plasma-assisted method to break down and reconstruct a natural precursor into an ordered graphitic structure. The synergistic combination of CNTs and VGNS overcomes the challenges intrinsic to both materials. The resulting VGNS/CNTs hybrids show a high specific capacitance with good cycling stability. The charge storage is based mainly on the non-Faradaic mechanism. In addition, a series of optimization experiments were conducted to reveal the critical factors that are required to achieve the demonstrated high supercapacitor performance.

A sensitive DNA enzyme-based fluorescent assay for bacterial detection.

Bacterial detection plays an important role in protecting public health and safety, and thus, substantial research efforts have been directed at developing bacterial sensing methods that are sensitive, specific, inexpensive, and easy to use. We have recently reported a novel “mix-and-read” assay where a fluorogenic DNAzyme probe was used to detect model bacterium E. coli. In this work, we carried out a series of optimization experiments in order to improve the performance of this assay. The optimized assay can achieve a detection limit of 1000 colony-forming units (CFU) without a culturing step and is able to detect 1 CFU following as short as 4 h of bacterial culturing in a growth medium. Overall, our effort has led to the development of a highly sensitive and easy-to-use fluorescent bacterial detection assay that employs a catalytic DNA.