Using loop-mediated isothermal amplification for fast species delimitation in eels (genus Anguilla), with special reference to the European eel (Anguilla anguilla)

Parvalbumin Gene: A Valuable Marker for Pike Authentication and Allergen Risk Assessment

Fish from the pike (Esox) genus are valued in gastronomy for their superior meat quality. However, they can cause allergic reactions in sensitive consumers. This work aimed to fill the gap in the detection of pike allergens using molecular-biological techniques. New, fast, and accurate loop-mediated isothermal amplification (LAMP) and real-time PCR (qPCR) assays were designed to detect pike DNA using the parvalbumin gene as a marker. LAMP was assessed by electrophoresis, SYBR green optical detection, and real-time fluorescence detection. The latter was the most sensitive, detecting as little as 0.78 ng of pike DNA; the qPCR detection limit was 0.1 ng. The LAMP analysis took 20-70 min, which is significantly faster than qPCR. The study provides reliable detection and quantification of the parvalbumin gene in both fresh and processed samples and further highlights the versatility of the use of the parvalbumin gene for the authentication of food products and consumer protection via refined allergen risk assessment that is independent of the type of tissue or food processing method used.

Recent advancements with loop-mediated isothermal amplification (LAMP) in assessment of the species authenticity with meat and seafood products

Species adulteration or mislabeling with meat and seafood products could negatively affect the fair trade, wildlife conservation, food safety, religion aspect, and even the public health. While PCR-based methods remain the gold standard for assessment of the species authenticity, there is an urgent need for alternative testing platforms that are rapid, accurate, simple, and portable. Owing to its ease of use, low cost, and rapidity, LAMP is becoming increasingly used method in food analysis for detecting species adulteration or mislabeling. In this review, we outline how the features of LAMP have been leveraged for species authentication test with meat and seafood products. Meanwhile, as the trend of LAMP detection is simple, rapid and instrument-free, it is of great necessity to carry out end-point visual detection, and the principles of various end-point colorimetry methods are also reviewed. Moreover, with the aim to enhance the LAMP reaction, different strategies are summarized to either suppress the nonspecific amplification, or to avoid the results of nonspecific amplification. Finally, microfluidic chip is a promising point-of-care method, which has been the subject of a great deal of research directed toward the development of microfluidic platforms-based LAMP systems for the species authenticity with meat and seafood products.

Visual and rapid detection of escolar (Lepidocybium flavobrunneum) using loop mediated isothermal amplification in conjunction with a specific molecular beacon probe

Species adulteration has become a main reason for the unexpected exposure to escolar, which is often related with the gastrointestinal disease called keriorrhea. Sensitive and accurate identification of escolar is required to protect consumers from commercial and health frauds. The present study established a visual and rapid method for escolar detection using LAMP (loop-mediated isothermal amplification) in conjunction with a MB (molecular beacon) probe. The visual MB-LAMP assay demonstrated high specificity and superb sensitivity (1 pg DNA) for escolar and low to 0.1 % (w/w) simulated adulteration could be detected within 25 min. Additionally, method validation on commercial products highlighted the umbrella term of white tuna for escolar on Chinese market. All these results indicated that the MB-LAMP method is a useful tool for rapid, sensitive and convenient detection of escolar and can also be used as a point-of-care molecular diagnostic technique since it does not require the expensive equipment.

Rapid analysis technologies with chemometrics for food authenticity field: A review

In recent years, the problem of food adulteration has become increasingly rampant, seriously hindering the development of food production, consumption, and management. The common analytical methods used to determine food authenticity present challenges, such as complicated analysis processes and time-consuming procedures, necessitating the development of rapid, efficient analysis technology for food authentication. Spectroscopic techniques, ambient ionization mass spectrometry (AIMS), electronic sensors, and DNA-based technology have gradually been applied for food authentication due to advantages such as rapid analysis and simple operation. This paper summarizes the current research on rapid food authenticity analysis technology from three perspectives, including breeds or species determination, quality fraud detection, and geographical origin identification, and introduces chemometrics method adapted to rapid analysis techniques. It aims to promote the development of rapid analysis technology in the food authenticity field.

Fast and User-Friendly Detection of Flatfish Species (Pleuronectes platessa and Solea solea) via Loop-Mediated Isothermal Amplification (LAMP)

The detection of a Cytochrome b gene (cytb) for species differentiation in fish is intensively used. A fast alternative to expensive and time-consuming DNA barcoding is loop-mediated isothermal amplification (LAMP) in combination with efficient readout systems. For this reason, we developed LAMP assays for rapid species detection of Pleuronectes platessa and Solea solea, two economically important flatfish species in Europe that are prone to mislabeling. Species-specific primer sets targeting cytb were designed, and LAMP assays were optimized. With the optimized LAMP assays, we were able to detect up to 0.1 and 0.01 ng of target DNA of P. platessa and S. solea, respectively, and in each case up to 1% (w/w) of target species in mixtures with nontarget species. For future on-site detection, a lateral flow assay and a pocket-sized lab-on-phone assay were used as readout systems. The lab-on-phone assay with the S. solea specific primer set revealed cross-reactivity to Solea senegalensis. The assay targeting P. platessa proved to be highly specific. Both assays could be performed within 45 min and provided rapid and easy detection of fish species.

Using loop-primer mediated PCR to enhance the detection of poorly preserved DNA

Ancient DNA is vitally important in evolutionary research, and obtaining authentic ancient DNA sequences is critical for a proper analysis. However, it is difficult to acquire amplicons accurately and efficiently from ancient DNA templates using current techniques. Here, we established a loop-primer-mediated amplification method (L-PCR) to obtain target ancient DNA sequences with high accuracy and efficiency. The method was tested using 66 ancient samples (including 27 pig bones or teeth and 39 chicken bones) and serially diluted modern animal DNA templates. Compared to nested PCR, L-PCR was proven to be more efficient and accurate and could obtain more amplicons from both ancient pig samples and chicken bones and detect as low as 10−3 ng/μl modern pig template DNA. The efficiency was at least 100-fold that of the nested PCR. The results suggest that L-PCR is advantageous for obtaining authentic DNA sequences from poorly preserved or recalcitrant ancient specimens.

Development of loop-mediated isothermal amplification (LAMP) assay for rapid and direct screening of yellowfin tuna (Thunnus albacares) in commercial fish products

Tuna is one of the most widely consumed fish on the European market, being available in various consumable options. Among them, Thunnus albacares, also called yellowfin tuna, is a delicacy and is consumed by millions of people around the world. Due to its comparatively high cost and demand, it is more vulnerable to fraud, where low-cost tuna or other fish varieties might be replaced for economic gain. In this study, a loop-mediated isothermal amplification (LAMP) assay was developed and validated for targeting the mitochondrial cytochrome b gene for fast and direct detection of Thunnus albacares, which is a valuable tuna species. The analytical specificity was confirmed using 18 target samples (Thunnus albacares) and 18 samples of non-target fish species. The analytical sensitivity of the LAMP assay was 540 fg DNA per reaction. In addition, a simple and direct swab method without time-consuming nucleic acid extraction procedures and the necessity for cost-intensive laboratory equipment was performed that allowed LAMP detection of Thunnus albacares samples within 13 minutes. Due to its high specificity and sensitivity, the LAMP assay can be used as a rapid and on-site screening method for identifying Thunnus albacares, potentially providing a valuable monitoring tool for food authenticity control by the authorities.

Visual detection of rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar) simultaneously by duplex loop-mediated isothermal amplification

Loop-mediated isothermal amplification (LAMP) is often confounded by the non-specific amplification arising from primer dimers, off-target priming, and other artifacts. Precipitation of the DNA produced during LAMP with the use of specific fluorescently labeled probe has proved the effectiveness in specific detection. Herein, two fluorophores (ROX and FAM) were attached to the primers S-LB-6 and R-FIP for Atlantic salmon and rainbow trout, respectively, which are self-quenched in unbound state and become de-quenched after binding to the dumbbell-shaped DNA specifically. The DNA precipitation and appearance of small sediment took 10 s of centrifugation at 1000 g, by adding polyethylenimine (PEI) 600. Each target species was specifically amplified with the predicted color of PEI-DNA sediment, namely red for Atlantic salmon, green for rainbow trout, and pale yellow for mixed species. The optimized duplex LAMP system has proved its specificity and can detect as little as 1 ng DNA in visual detection.

Rapid identification of Amanita citrinoannulata poisoning using colorimetric and real-time fluorescence and loop-mediated isothermal amplification (LAMP) based on the nuclear ITS region

Health concerns and financial losses caused by mushroom poisoning have been reported worldwide. Amanita citrinoannulata, a poisonous mushroom commonly found in China, results in a toxic reaction in humans after mistaken ingestion. To reduce the mistaken ingestion of poisonous mushrooms and to improve clinical diagnosis of mushroom poisoning, a rapid mushroom species identification method is required. Such identification methods could be advantageous in the identification of other poisonous mushroom species. This study developed two rapid and sensitive methods for the detection of A. citrinoannulata utilizing colorimetric and real-time loop-mediated isothermal amplification (LAMP) technology and specifically designed primers for the internal transcribed spacer (ITS) genes of A. citrinoannulata. The methods demonstrated high sensitivity as 0.2 ng of A. citrinoannulata DNA could be detected, with no cross-reaction with 41 non-target mushroom species. The entire detection process could be completed within 40 min without requiring complex instruments and can be observed by the naked eye. Therefore, these novel methods can be used for the identification of fresh and cooked mushroom samples and vomit samples, which contain only 1% A. citrinoannulata. Furthermore, these methods facilitate the detection of mushroom poisoning, and thus, have potential to reduce the number of mushroom poisoning-related deaths worldwide.

Establishment and Evaluation of a Loop-Mediated Isothermal Amplification Assay for Rapid Detection of Pseudomonas fluorescens in Raw Milk

Raw milk is susceptible to microbial contamination during transportation and storage. Pseudomonas fluorescens producing heat-resistant enzymes have become the most common and harmful psychrophilic microorganisms in the cold chain logistics of raw milk. To rapidly detect P. fluorescens in raw milk, the protease gene aprX was selected as a detection target to construct a set of primers with strong specificity, and a loop-mediated isothermal amplification (LAMP) assay was established. The detection thresholds of the LAMP assay for pure cultured P. fluorescens and pasteurized milk were 2.57 × 10² and 3 × 10² CFU/mL, respectively. It had the advantages over conventional method of low detection threshold, strong specificity, rapid detection, and simple operation. This LAMP assay can be used for online monitoring and on-site detection of P. fluorescens in raw milk to guarantee the quality and safety of dairy products.

Rapid in-situ detection kit (RisK): Development of loop-mediated isothermal amplification (LAMP) assay for the rapid identification of selected invasive alien fish in Malaysian freshwaters

Invasive alien fish species have become a silent treat towards the ecosystem especially the native fish population in Malaysia. There has been a need to develop rapid identification methods that can aid management teams in identifying fish species that are not native to our ecosystem. Current visual identification methods are highly tedious and require time, delaying action towards curbing the invasion. The LAMP assay successfully identified six popular invasive fish species in Malaysia. None of the LAMP assays showed false positives and the Limit of Detection of the LAMP primers were highly sensitive and could detect DNA samples up to 1 × 10^-15 ng/μl. The LAMP primers designed were highly specific to the target species and did not amplify non target species. DNA sequencing was done to ensure the accuracy of LAMP assay results. This study demonstrates that LAMP is a suitable tool in species identification efforts of invasive fish species in Malaysia.

Rainbow trout (Oncorhynchus mykiss) identification in processed fish products using loop-mediated isothermal amplification and polymerase chain reaction assays

BACKGROUND

Financial loss and health risk caused by the substitution of rainbow trout for other salmonid species have become a common issue around the world. The situation could be further exacerbated in China by the 'abused' common name of San Wen Yu (the corresponding Chinese ideogram ) for salmonids, considering the absence of a standardized naming system for seafood species. To prevent such episodes, the present study aimed to develop novel loop-mediated isothermal amplification (LAMP) and polymerase chain reaction (PCR) assays targeting the mitochondrial cytochrome b gene for rapid identification of rainbow trout in processed fish products.

RESULTS

Rainbow trout-specific primers (LAMP and PCR) were designed, and the specificity against 23 different fish species was confirmed. The minimum amount of detectable DNA for LAMP assay reached 500 pg, up to 10-fold less than for PCR assay. In addition to agarose gel electrophoresis, naked-eye inspection of the LAMP-positive samples using SYBR Green I under daylight or ultraviolet light was also validated. Finally, commercial San Wen Yu products made from rainbow trout could be accurately identified using the newly developed LAMP and PCR assays, further cross-confirmed by mini DNA barcoding and neighbor-joining dendrograms.

CONCLUSIONS

The LAMP and PCR assays established in the study allow a fast and accurate identification of rainbow trout in processed fish products. © 2020 Society of Chemical Industry.