Preparation of an In-House Reference Material Containing Fumonisins in Thai Rice and Matrix Extension of the Analytical Method for Japanese Rice

Mycotoxin contamination in rice is less reported, compared to that in wheat or maize, however, some Fusarium fungi occasionally infect rice in the paddy field. Fumonisins are mycotoxins mainly produced by Fusarium verticillioides, which often ruins maize. Rice adherent fungus Gibberella fujikuroi is taxonomically near to F. verticillioides, and there are sporadic reports of fumonisin contamination in rice from Asia, Europe and the United States. Therefore, there exists the potential risk of fumonisin contamination in rice as well as the need for the validated analytical method for fumonisins in rice. Although both natural and spiked reference materials are available for some Fusarium mycotoxins in matrices of wheat and maize, there are no reference materials for Fusarium mycotoxins in rice. In this study, we have developed a method for the preparation of a reference material containing fumonisins in Thai rice. A ShakeMaster grinding machine was used for the preparation of a mixed material of blank Thai rice and F. verticillioides-infected Thai rice. The homogeneity of the mixed material was confirmed by one-way analysis of variance, which led this material to serve as an in-house reference material. Using this reference material, several procedures to extract fumonisins from Thai rice were compared. Accordingly, we proved the applicability of an effective extraction procedure for the determination of fumonisins in Japanese rice

Immunosensing of Aflatoxin B1 and Ochratoxin A on a Portable Device as Point-of-Care

Aflatoxin B1 (AFB1) and ochratoxin A (OTA) are potent mycotoxins produced by the fungal genus Aspergillus. Their occurrence in grain corn is alarming hence the need for rapid on-site detection. An immuno-based biosensor technique for detection of the aforementioned toxins is described here. Highly specific in-house polyclonal antibodies against AFB1 and OTA were employed as bioreceptors in a label-free electrochemical biosensor; immobilized on modified screen-printed carbon electrodes (SPCEs). The immuno-functionalized SPCEs were first characterized on a laboratory electrochemical workstation for proof-on-concept study using differential pulse voltammetry (DPV) electrochemical technique. An Android-based device is improvised as a portable electrochemical reader integrated with internet of thing (IoT) features which include cloud server and a dedicated website. Sensitivity achieved by the modified SPCEs on the portable device is superior compared to enzyme-linked immunosorbent assay (ELISA) method and lab-based electrochemical workstation. The miniaturized biosensor system has been successfully tested on cornfield for in-situ mycotoxins detection with simple sample extraction. Analysis performed on twenty samples were validated using chromatographic analysis. This biosensor-IoT system offers a potential application for real-time detection and the portable reader serves as an excellent tool for point-of-care in routine monitoring of harmful mycotoxins

Preparation of an In-House Reference Material Containing Fumonisins in Thai Rice and Matrix Extension of the Analytical Method for Japanese Rice

Mycotoxin contamination in rice is less reported, compared to that in wheat or maize, however, some Fusarium fungi occasionally infect rice in the paddy field. Fumonisins are mycotoxins mainly produced by Fusarium verticillioides, which often ruins maize. Rice adherent fungus Gibberella fujikuroi is taxonomically near to F. verticillioides, and there are sporadic reports of fumonisin contamination in rice from Asia, Europe and the United States. Therefore, there exists the potential risk of fumonisin contamination in rice as well as the need for the validated analytical method for fumonisins in rice. Although both natural and spiked reference materials are available for some Fusarium mycotoxins in matrices of wheat and maize, there are no reference materials for Fusarium mycotoxins in rice. In this study, we have developed a method for the preparation of a reference material containing fumonisins in Thai rice. A ShakeMaster grinding machine was used for the preparation of a mixed material of blank Thai rice and F. verticillioides-infected Thai rice. The homogeneity of the mixed material was confirmed by one-way analysis of variance, which led this material to serve as an in-house reference material. Using this reference material, several procedures to extract fumonisins from Thai rice were compared. Accordingly, we proved the applicability of an effective extraction procedure for the determination of fumonisins in Japanese rice

Fluorescence-based immunoassay for the detection of Xanthomonas oryzae pv. oryzae in rice leaf

The identification of rice bacterial leaf blight disease requires a simple, rapid, highly sensitive, and quantitative approach that can be applied as an early detection monitoring tool in rice health. This paper highlights the development of a turn-off fluorescence-based immunoassay for the early detection of Xanthomonas oryzae pv. oryzae (Xoo), a gram-negative bacterium that causes rice bacterial leaf blight disease. Antibodies against Xoo bacterial cells were produced as specific bio-recognition molecules and the conjugation of these antibodies with graphene quantum dots and gold nanoparticles was performed and characterized, respectively. The combination of both these bio-probes as a fluorescent donor and metal quencher led to changes in the fluorescence signal. The immunoreaction between AntiXoo-GQDs, Xoo cells, and AntiXoo-AuNPs in the immuno-aggregation complex led to the energy transfer in the turn-off fluorescence-based quenching system. The change in fluorescence intensity was proportional to the logarithm of Xoo cells in the range of 100–105 CFU mL−1. The limit of detection was achieved at 22 CFU mL−1 and the specificity test against other plant disease pathogens showed high specificity towards Xoo. The detection of Xoo in real plant samples was also performed in this study and demonstrated satisfactory results