Xiujiang Li's research while affiliated with Nanchang University and other places

Conventional immunochromatographic test strips (ICSs) based on gold nanoparticle (AuNP) probes offer limited sensitivity. Here, AuNPs were separately labeled with monoclonal or secondary antibodies (MAb or SAb). In addition, spherical, homogeneously dispersed, and stable selenium nanoparticles (SeNPs) were also synthesized. By optimizing the preparation parameters, two ICSs based on the dual AuNP signal amplification (Duo-ICS) or SeNPs (Se-ICS) were developed for the rapid detection of T-2 mycotoxin. The detection sensitivities of the Duo-ICS and Se-ICS assays for T-2 were 1 ng/mL and 0.25 ng/mL, respectively, which were 3-fold and 15-fold more sensitive, respectively, than a conventional ICS. Furthermore, the ICSs were applied in the detection of T-2 in cereals, which requires higher sensitivity. Our findings indicate that both ICS systems can be used for rapid, sensitive, and specific detection of T-2 toxin in cereals and potentially other sample types.

(1) Background: Medicinal and edible food and traditional Chinese medicine have been used to treat various diseases. However, their safety has not been thoroughly assessed. (2) Methods: An immunochromatographic test strip (ICS) was used for the first time to screen some mycotoxins, including aflatoxin B1 (AFB1), zearalenone (ZEN), and T-2 toxin, in medicinal and edible food and traditional Chinese medicine. Antibody/nano-gold particle coupling was used with the prepared ICS, and the pH, monoclonal antibody concentration, and antigen amount were optimized. The extraction sample solution was diluted 10 times with phosphate-buffered saline containing 0.5% Tween-20 and 0.05% sodium dodecyl sulfate to remove the complex matrix in medicinal and edible food. (3) Results: Under optimal conditions, the sensitivities of the developed ICS for AFB1, ZEN, and T-2 were 0.5, 5.0, and 5.0 ng/mL, respectively. Among the 30 medicinal and edible food samples tested, two samples (both of sand jujube kernels) were positive, and the results were verified by high-performance liquid chromatography and enzyme-linked immunosorbent assay and were consistent with the ICS test results. (4) Conclusions: The ICS could be used for rapid screening and simultaneous detection of mycotoxins at medicinal and edible food storage facilities.

Monascus, which is traditionally used in various Asian industries, produces several secondary metabolites during the fermentation process, including citrinin, a toxin whose impact limits the development of the Monascus industry. We have previously found that the addition of 2.0 g/L genistein to Monascus medium reduces citrinin production by approximately 80%. Here, we explored the molecular mechanisms whereby genistein affects citrinin production. We sequenced the Monascus genome and performed transcriptome analysis on genistein-treated and -untreated groups. Comparison between the two groups showed 378 downregulated and 564 upregulated genes. Among the latter, we further examined the genes related to citrinin biosynthesis and quantified them using quantitative real-time polymerase chain reaction (qRT-PCR). Genes orf5, pksCT, orf3, orf1, orf6, and ctnE were significantly downregulated, demonstrating that genistein addition indeed affects citrinin synthesis. Our results may lay the groundwork for substantial improvements in the Monascus fermentation industry.

Mycotoxins, such as fumonisin B1 (FB1) and deoxynivalenol (DON), are toxic secondary metabolites produced by fungi. Herein, the simultaneous detection of FB1 and DON (both of which are water-soluble) in grain samples by immunochromatographic methods was used to probe whether the levels of these mycotoxins exceeded the limit of 1 mg/kg. Two types of immunochromatographic test strips (ICSs) were developed for this purpose, namely, those based on Au nanospheres (prepared via reduction with trisodium citrate) and Au nanoflowers (prepared by Au seed-mediated growth) as markers, with the respective sensitivities to both FB1 and DON equalling 20 and 5.0 ng/mL. The former ICS was used to detect FB1 and DON in grain (51 wheat samples and 18 maize samples), providing results consistent with those of high-performance liquid chromatography and enzyme-linked immunosorbent assays. The developed technique was suitable for the on-site screening of large-scale samples for FB1 and DON.

Monascus comprises purple-red molds. Various compounds can be obtained from these species, including statins and food-safe yellow, red, and orange pigments. However, the secondary metabolite citrinin, a mycotoxin, is produced during the late stages of growth. Citrinin biosynthesis should be reduced to apply Monascus pigments safely. Fortunately, this can be achieved by the addition of flavonoids (genistein, daidzein, apigenin, and kaempferol) . However, the effects of these flavonoids on other metabolites remain unknown. Here, we report a ¹H-NMR-based multivariate metabolomic analysis of the effects of flavonoids on mycotoxin citrinin production by Monascus. Fifteen metabolites involved in lysine and arginine biosynthesis and alanine, aspartate, glutamate, biotin, arginine, proline, and glutathione metabolism were detected. The reduction in glutamate, aspartate, biotin, and 2-phosphoglycerate content suggested their association with the citrinin reduction mechanism. This study identifies the citrinin production pathway in Monascus and will aid in the development of citrinin-control methods.

Monascus mold produces useful bioactive compounds such as Monascus pigments, monacolin K, and ergosterol. In this study, metabolomics analysis was used to investigate the metabolic profile changes in Monascus aurantiacus Li AS3.4384 (MALA) induced by genistein at different fermentation times using UHPLC-Q-TOF-MS/MS. The addition of genistein was found to not only reduce citrinin but also suppress significant differential metabolites. A total of 21 significant differential metabolites were involved in the most significant metabolic pathways (impact >0.1). These metabolites affected the aspartic acid, glutamic acid pathway, tricarboxylic acid (TCA) cycle, pyruvate synthesis pathway, and lysine degradation pathway. Thus, the addition of genistein may change the precursor for citrinin synthesis of Monascus. These findings provide significant insight into the Monascus metabolic pathways affected by genistein and will help to improve the quality control and safety of Monascus in food and supplements.

Monascus can produce many beneficial metabolites; however, it can simultaneously also produce citrinin, which seriously limits its application. Therefore, reducing the production of citrinin is of great interest. Herein, Monascus aurantiacus Li AS3.4384 (MAL) was used to optimize the liquid-state fermentation process and investigate the effects of genistein and other flavonoids on citrinin, pigments, and biomass of MAL. Results showed that citrinin decreased by 80%, pigments and biomass increased by approximately 20% in 12 days with addition of 20.0 g/L rice powder as a carbon source and 2.0 g/L genistein during shaking liquid-state fermentation. Further, genistein, daidzein, luteolin, apigenin, quercetin, baicalein, kaempferol myricetin, and genistin exerted different effects on citrinin production by MAL, with genistein causing the highest reduction in citrinin production during liquid-state fermentation, possibly due to the presence of C5-OH, C4'-OH, and C7-OH. Therefore, genistein can be added to the fermentation process of Monascus to reduce citrinin.

The mycotoxin citrinin is often produced during fermentation of Monascus products. We studied the effects of flavonoids on citrinin production by Monascus aurantiacus Li AS3.4384 (MALA) by adding rutin, α-glucosylrutin, or troxerutin to the fermentation medium, in a first-of-its-kind study. Appropriate amounts of rutin, α-glucosylrutin, or troxerutin did not affect normal mycelial growth. Addition of 5.0 g/l of rutin only weakly reduced (29.2%) citrinin production, relative to inhibition by 5 g/l α-glucosylrutin or troxerutin (by 54.7% and 40.6%, respectively). In starch inorganic liquid culture media, addition of 20.0 g/l of troxerutin, followed by fermentation for 12 days, reduced citrinin yield by 75.26%. Addition of 15.0 g/l of troxerutin to low-starch peptone liquid fermentation media reduced citrinin yield by 87.9% after 14 days of fermentation, and addition of 30.0 g/l troxerutin to yeast extract sucrose liquid media for 12 days reduced citrinin yield by 53.7%.

BACKGROUND Monascus, a filamentous fungus, produces many bioactive substances. However, in the process of fermentation, Monascus also produces the mycotoxin citrinin. Owing to the presence of citrinin, the safety of Monascus products has been questioned and their wide application limited. Using soybean isoflavones (SI) as exogenous additives, alterations in citrinin production by Monascus aurantiacus Li AS3.4384 (MALA) in different media used for liquid state fermentation were investigated. RESULTS Results showed that the citrinin concentration was 95.98% lower than that of the control group after 16‐days fermentation when 20.0 g L⁻¹ SI were added to rice powder and inorganic salt medium. Citrinin production was reduced by 97.24% after 12‐days fermentation with 10.0 g L⁻¹ SI in starch inorganic salt medium; 82.52% after 20‐days fermentation with 20.0 g L⁻¹ SI in starch peptone medium with high starch content; 45.07% after 14‐days fermentation with 5.0 g L⁻¹ SI in starch peptone medium with low starch content; and 82.21% after 14‐days fermentation with 20.0 g L⁻¹ SI in yeast extract sucrose medium. CONCLUSION The developed method of removing citrinin is simple, safe, and effective, and it can be applied to reduce the citrinin content of Monascus products. © 2019 Society of Chemical Industry