Application of species-specific PCR for the identification of dried bonito product (Katsuobushi)

Twenty-three years of PCR-based seafood authentication assay development: What have we learned?

Seafood is a prime target for fraudulent activities due to the complexity of its supply chain, high demand, and difficult discrimination among species once morphological characteristics are removed. Instances of seafood fraud are expected to increase due to growing demand. This manuscript reviews the application of DNA-based methods for commercial fish authentication and identification from 2000 to 2023. It explores (1) the most common types of commercial fish used in assay development, (2) the type of method used, (3) the gene region most often targeted, (4) provides a case study of currently published assays or primer-probe pairs used for DNA amplification, for specificity, and (5) makes recommendations for ensuring standardized assay-based reporting for future studies. A total of 313 original assays for the detection and authentication of commercial fish species from 191 primary articles published over the last 23 years were examined. The most explored DNA-based method was real-time polymerase chain reaction (qPCR), followed by DNA sequencing. The most targeted gene regions were cytb (cytochrome b) and COI (cytochrome c oxidase 1). Tuna was the most targeted commercial fish species. A case study of published tuna assays (n = 19) targeting the cytb region found that most assays were not species-specific through in silico testing. This was conducted by examining the primer mismatch for each assay using multiple sequence alignment. Therefore, there is need for more standardized DNA-based assay reporting in the literature to ensure specificity, reproducibility, and reliability of results. Factors, such as cost, sensitivity, quality of the DNA, and species, should be considered when designing assays.

Quality, functionality, and microbiology of fermented fish: a review

Fermentation is a traditional food preservation method and is widely used for improving food safety, shelf life, and organoleptic and nutritional attributes. Fermented fish are produced and consumed in different parts of the world and are an integral part of many food cultures. Furthermore, fermented fish are a source of interesting microbes and are an important industry in many countries. This review tries to update the types and manufacturing processes for fermented fish around the world. The emphasis is on this work related to fermented fish and their health benefits, as well as the contribution of microorganisms to their fermentation. A variety of different approaches have been used to determine and understand microbial composition and functionality. Moreover, some challenges and future research directions regarding fermented fish are also discussed in this review. Further research into fermented fish products is of crucial importance not only for the food industry but also for human health. However, extensive in vivo and toxicological studies are essential before the application of bioactive-rich fermented fish products for human health benefits.

Immunostimulatory effect of dried bonito extract on mouse macrophage cell lines and mouse primary peritoneal macrophages

Dried bonito is a preserved food used in Japan, which contains abundant flavor ingredients and functional substances. We focused on the immunostimulatory effect of dried bonito extract (DBE) on mouse macrophage-like J774.1 cells, RAW264.7 cells, and mouse primary peritoneal macrophages. DBE significantly stimulated the production of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) by both J774.1 cells and peritoneal macrophages by enhancing the cytokine gene expression levels. In addition, DBE stimulated nitric oxide production by enhancing the expression of inducible nitric oxide synthase in RAW264.7 cells. DBE also increased the phagocytosis activity of J774.1 cells. Immunoblot analysis revealed that DBE has an immunostimulatory effect on macrophages through activation of mitogen-activated protein kinase and nuclear factor-κB cascades. TNF-α production enhanced by DBE was partially inhibited by treatment with TLR4 inhibitor TAK-242, whereas IL-6 production enhanced by DBE was almost inhibited. These results suggested that DBE is thought to strongly stimulate the TLR4 signaling pathway for macrophage activation, and its activation is also involved in other signaling. Finally, the phagocytosis activity of peritoneal macrophages from DBE-administered BALB/c mice increased significantly, suggesting that DBE has the potential to stimulate macrophage activity in vivo. In conclusion, these data indicated that DBE contributes to activating host defense against pathogens by activating innate immunity.

Advances in DNA-based techniques for the detection of seafood species substitution on the commercial market

Increased worldwide trade and processing of seafood has increased the potential for species substitution on the commercial market. To detect and prevent species substitution, several deoxyribonucleic acid (DNA)-based methods have been developed that can be used to identify species in a variety of food types. For large-scale applications, such as regulatory screening, these methods must be rapid, cost-effective, reliable, and have high potential for automation. This review highlights recent technological advances in DNA-based identification methods, with a focus on seafood species identification in automated, high-throughput settings. Advances in DNA isolation methods include silica-based columns for use in high-throughput operations and magnetic bead particles for increased and targeted recovery of DNA. The three most widely used methods for seafood species identification (polymerase chain reaction [PCR] sequencing, PCR-restriction fragment length polymorphism, and species-specific PCR) will be discussed, with a focus on the incorporation of technologies such as rapid PCR cycling, microfluidic chips, and real-time PCR. Emerging methods, including DNA microarrays and next-generation sequencing will also be explored for their potential to identify seafood species on a large scale. Overall, many of the technological advances discussed here offer complementary properties that will enable species identification in a variety of settings and with a range of products.

Identification of causative agents and species in shrimp implicated in a food poisoning case in Taiwan

The possible causative agent and shrimp species involved in a bait shrimp poisoning case that occurred in northern Taiwan was determined. Because the patient's symptoms were similar to those caused by boric acid and slightly similar to those caused by sulfite, the concentrations of boric acid and sulfite (as sulfur dioxide) in the patient's vomitus and in shrimp collected from bait stores and markets were analyzed. The concentration of boric acid was 36.8 to 37.1 mg/g in the patient's vomitus, 1.4 to 3.8 mg/g in shrimp meats obtained from bait stores, and not detectable (less than 0.001 mg/g) in shrimp meat obtained from commercial markets. No significant differences in sulfur dioxide concentrations (0.067 to 0.088 mg/g) were found in patient's vomitus and the shrimp meat from both bait stores and commercial markets. A fragment of the cytochrome b gene (∼406 bp) was amplified by PCR using a pair of primers (UCYTB151F and UCYTB270R) from shrimp meat of two species and the vomitus. The vomited shrimp was identified as Parapenaeus fissuroides on the basis of gene sequencing and restriction fragment length polymorphism patterns after treatment with endonuclease Alu I. Based on the patient's symptoms and analytical data, we concluded that boric acid at toxic levels had been illegally added to the bait shrimp P. fissuroides.

Species identification and vitamin A level in lutjanid fish implicated in vitamin A poisoning

One outbreak of food poisoning associated with ingestion of the liver of a large lutjanid fish was investigated in this study. The symptoms in three patients primarily included headache, nausea, vomiting, fever, vertigo, and visual disorientation and later included peeling of the skin. The species of fish implicated in this incident was Etelis carbunculus (family Lutjanidae) as determined by direct sequence analysis and PCR plus restriction fragment length polymorphism analysis for detection of the cytochrome b gene. Subsequently, several specimens of E. carbunculus of different body weights were collected, and the level of vitamin A in the muscle and liver was determined by high-performance liquid chromatography. The average level of vitamin A in E. carbunculus muscle was 12 +/- 2 IU/g and that in the liver was 9,844 +/- 7,812 IU/g. Regression models indicate that E. carbunculus with higher body weight and liver weight will have higher levels of vitamin A levels in the liver.

Species identification of ciguatoxin-carrying grouper implicated in food poisoning

Food poisoning due to ingestion of an unknown red grouper occurred in southern Taiwan. To identify the species of toxic red grouper implicated in food poisoning, a 475-bp sequence of the cytochrome b gene from six species of fresh red grouper meat was amplified by using a pair of primers (L14735/H15149). This fragment could be amplified when fish meat was treated with different heating processes. After sequencing, it was found that no variation in sequences was detected among individuals within each species. The species of toxic red grouper meat implicated in food poisoning was judged to be Lutjanus bohar based on sequence analysis. In addition, restriction enzyme analysis with HaeIII rapidly distinguished these six species of red grouper and the two samples implicated in food poisoning. No toxicity of viscera in 18 specimens of six red grouper species was detected, but two food poisoning samples were found to be toxic. This study indicated that DNA sequence and restriction enzyme analysis are powerful methods for identifying potentially toxic red grouper species as L. bohar.