Development of a loop-mediated isothermal amplification method for the rapid detection of the dioxin-degrading bacterium Ochrobactrum anthropi in soil

Authentication of olive oil in commercial products using specific, sensitive, and rapid loop-mediated isothermal amplification

Olive oil is an important and popularly used plant oil in the daily diet or chemical industry. Due to its biological benefits on human health and higher selling prices, adulteration of olive oil for commercial fraud by other plant oils is becoming a serious issue. In this study, a specific, sensitive and rapid loop-mediated isothermal amplification (LAMP) was first developed for the detection of Olea europaea DNA for olive oil authentication. The oleosin gene was used for the primer design of the LAMP assay. After primer validation, the results showed that the LAMP primers were specific and rapid to isothermally authenticate the oleosin gene of Olea europaea within 1 h at 62 °C and had no cross-reaction with other DNA of plant oils. The sensitivity of LAMP was 1 ng of genomic DNA in olive oil, and only 1% olive oil in the sample was requisite during DNA amplification. Additionally, positive detection by LAMP in all the collected commercial olive oil products was practically performed but not in PCR assays. In conclusion, herein, the established LAMP assay with specificity could not only be capable for rapid identification but also applicable for olive oil authentication for precluding adulteration in plant oil products.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05726-y.

Specific, sensitive and rapid Curcuma longa turmeric powder authentication in commercial food using loop-mediated isothermal nucleic acid amplification

Turmeric (Curcuma longa) is a rhizomatous plant of the ginger family Zingiberaceae that is usually dried and ground into powder for use as a seasoning. Because turmeric has become increasingly popular in the functional food market, adulteration of C. longa by other turmeric species is becoming an increasingly significant problem. In this study, loop-mediated isothermal amplification (LAMP) was developed for the detection of C. longa DNA for turmeric authentication. ITS2-26S rDNA was used for the LAMP primer designation. The results demonstrated that the specific primers exhibited high specificity, authenticated C. longa DNA within 30 min at 65 °C isothermally and had no cross-reaction with other adulterants. LAMP was sensitive to 0.1 ng of turmeric C. longa DNA, and only 0.01% of C. longa turmeric powder in the sample was required for DNA amplification. The sensitivity of LAMP was 10-fold higher than that of PCR (0.1%) from a previous report. Moreover, all the collected commercial turmeric products were positively detected by LAMP and RtF-LAMP (real-time fluorescence LAMP). The developed LAMP assay not only had higher specificity and rapidity than that of other methods but could also be applied to authenticate turmeric to prevent adulteration in food products.

Development of a specific isothermal nucleic acid amplification for the rapid and sensitive detection of shrimp allergens in processed food

Food allergens that cause anaphylactic reactions have become an important health problem worldwide. Among them, shrimp is a popular seafood in many cuisines. The best way to avoid allergic reactions is to mitigate the intake of food allergens. In this study, a loop-mediated isothermal amplification (LAMP) assay was developed for the detection of shrimp DNA. Using LAMP primers, the identification of shrimp DNA by the LAMP assay was specific and rapid (within 30 min). It exhibited no cross-reaction with the DNA of other Crustacea, including crabs and lobster, and at least 0.01% shrimp DNA existed in the test sample. Additionally, the sensitivity of LAMP for detecting shrimp DNA was 100-fold greater than that of conventional PCR. LAMP for the detection of shrimp DNA was reproducible regardless of whether the genomic DNA was extracted from boiled, steamed or roasted shrimp samples. In summary, the LAMP assay established herein not only could be potentially used for diagnosing shrimp DNA but could also be applicable for identifying shrimp allergens in commercial food products in marketplaces.

Development of loop-mediated isothermal amplification (LAMP) assays for the rapid detection of allergic peanut in processed food

Peanut is a widely and common used in many cuisines around the world. However, peanut is also one of the most important food allergen for causing anaphylactic reaction. To prevent allergic reaction, the best way is to avoid the food allergen or food containing allergic ingredient such as peanut before food consuming. Thus, to efficient and precisely detect the allergic ingredient, peanut or related product, is essential and required for maintain consumer's health or their interest. In this study, a loop-mediated isothermal amplification (LAMP) assay was developed for the detection of allergic peanut using specifically designed primer sets. Two sets of the specific LAMP primers respectively targeted the internal transcribed sequence 1 (ITS1) of nuclear ribosomal DNA sequence regions and the ara h1 gene sequence of Arachia hypogeae (peanut) were used to address the application of LAMP for detecting peanut in processed food or diet. The results demonstrated that the identification of peanut using the newly designed primers for ITS 1 sequence is more sensitive rather than primers for sequence of Ara h1 gene when performing LAMP assay. Besides, the sensitivity of LAMP for detecting peanut is also higher than the traditional PCR method. These LAMP primers sets showed high specificity for the identification of the peanut and had no cross-reaction to other species of nut including walnut, hazelnut, almonds, cashew and macadamia nut. Moreover, when minimal 0.1% peanuts were mixed with other nuts ingredients at different ratios, no any cross-reactivity was evident during performing LAMP. Finally, genomic DNAs extracted from boiled and steamed peanut were used as templates; the detection of peanut by LAMP was not affected and reproducible. As to this established LAMP herein, not only can peanut ingredients be detected but commercial foods containing peanut can also be identified. This assay will be useful and potential for the rapid detection of peanut in practical food markets.

Isothermal assay targeting class 1 integrase gene for environmental surveillance of antibiotic resistance markers

Antimicrobial resistance genes (ARGs) present in the environment pose a risk to human health due to potential for transfer to human pathogens. Surveillance is an integral part of mitigating environmental dissemination. Quantification of the mobile genetic element class 1 integron-integrase gene (intI1) has been proposed as a surrogate to measuring multiple ARGs. Measurement of such indicator genes can be further simplified by adopting emerging nucleic acids methods such as loop mediated isothermal amplification (LAMP). In this study, LAMP assays were designed and tested for estimating relative abundance of the intI1 gene, which included design of a universal bacteria 16S rRNA gene assay. Following validation of sensitivity and specificity with known bacterial strains, the assays were tested using DNA extracted from river and lake samples. Results showed a significant Pearson correlation (R² = 0.8) between the intI1 gene LAMP assay and ARG relative abundance (measured via qPCR). To demonstrate the ruggedness of the LAMP assays, experiments were also run in the hands of relatively "untrained" personnel by volunteer undergraduate students at a local community college using a hand-held real-time DNA analysis device - Gene-Z. Overall, results support use of the intI1 gene as an indicator of ARGs and the LAMP assays exhibit the opportunity for volunteers to monitor environmental samples for anthropogenic pollution outside of a specialized laboratory.

The development of loop-mediated isothermal amplification (LAMP) assays for the rapid authentication of five forbidden vegetables in strict vegetarian diets

Plant-based food ingredients such as garlic, Chinese leek, Chinese onion, green onion and onion are widely used in many cuisines around the world. However, these ingredients known as the “five forbidden vegetables” (FFVs) are not allowed in some vegetarian diets. In this study, a loop-mediated isothermal amplification (LAMP) assay was developed for the detection of FFVs using five respective LAMP primer sets. The specific primers targeted the ITS1-5.8S-ITS2 nuclear ribosomal DNA sequence regions among the five vegetables. The results demonstrated that the identification of FFVs using the newly developed LAMP assay is more sensitive than the traditional PCR method. Using pepper, basil, parsley, chili and ginger as references, established LAMP primer sets showed high specificity for the identification of the FFV species. Moreover, when FFVs were mixed with other plant ingredients at different ratios (100:0, 50:50, 20:80, 10:90, 5:95, 2:98, and 1:99), no cross-reactivity was evident using LAMP. Finally, genomic DNAs extracted from boiled and steamed FFVs in processed foods were used as templates; the performance of the LAMP reaction was not influenced using validated LAMP primers. Not only can FFV ingredients be identified but commercial foods containing FFVs can also be authenticated. This LAMP method will be useful for the authentication of FFVs in practical food markets in the future.