Development of a real-time PCR assay for rapid screening of acetic acid bacteria as a group in food products

Molecular Detection of Acetobacter aceti and Acetobacter pasteurianus at Different Stages of Wine Production

Acetobacter aceti and Acetobacter pasteurianus belong to acetic acid bacteria (AAB), associated with wine spoilage. The timely detection of AAB, thought essential for their control, is however challenging due to the difficulties of their isolation. Thus, it would be advantageous to detect them using molecular methods at all stages of winemaking and storage. In this paper, we analyzed wines, musts and grapes of 13 varieties grown in different regions with Protected Geographical Indication of the Republic of Moldova for the presence of AAB, Acetobacter aceti and Acetobacter pasteurianus by real-time PCR and measured wine volatile acidity. Overall, the AAB content in the mature wine explained 33.7% of the variance in the volatile acidity of the mature wine, while the A. pasteurianus content in the mature wine alone explained 59.6% of the variability in the volatile acidity in the wine, and its content in the grapes, must and wine explained about 70% of the variance in the the volatile acidity. This makes A. pasteurianus a good candidate to be a potential predictor of wine volatile acidity.

Sensitive colorimetric detection of Escherichia coli in milk using Au@Ag core-shell nanoparticles

Escherichia coli (E. coli) is a prevalent pathogen that is frequently associated with the foodborne illness. It causes various infections and poses a significant threat to human health. A rapid and sensitive assay for detecting E. coli is essential for timely diagnosis. Herein, a simple and sensitive colorimetric analysis method for detecting E. coli was developed based on the formation of Au@Ag core-shell nanoparticles facilitated by p-benzoquinone (BQ). E. coli reduced p-benzoquinone to generate hydroquinone (HQ), which could reduce the added Tollens' reagent to silver elemental and grow on the surface of gold nanoparticles (AuNPs). As the E. coli concentration increased, the silver layer thickess on the AuNPs surface growed, resulting in a stronger silver absorption peak observed at 390 nm. The color of the solution changed from red to orange, which could be used to detect E. coli by the naked eye. As a result, E. coli was detected with a linear range from 1.0 × 101 to 1.0 × 107 CFU/mL based on the absorbance intensity. In addition, this method accurately detected E. coli in real milk sample, demonstrating promising applications in foodborne pathogen detection. With satisfactory accuracy, the proposed colorimetric method holds excellent prospects in detecting pathogens in actual food samples.

Ag+-gated peroxidase activity of gold nanoparticles for sensitive detection of Escherichia coli

Escherichia coli (E. coli) is one of the most ubiquitous foodborne pathogens that can cause infections and threaten human health. Herein, a colorimetric method for sensitive detection of E. coli was established by using enzyme-nanozyme cascade reaction for signal amplification. Gold nanoparticles (AuNPs) are well-known nanozymes due to their high peroxidase-like activity. When the dense cetyltrimethylammonium bromide (CTAB) membrane on the surfaces of AuNPs kept the substrate away from AuNPs, the peroxidase activity of AuNPs was inhibited. However, the CTAB membrane could be disrupted by Ag⁺, resulting in enhanced peroxidase activity of AuNPs. When E. coli was present, the enzyme-nanozyme cascade reaction was initiated. The substrate p-aminophenyl β-D-galactopyranoside (PAPG) was hydrolyzed to the reductive p-aminophenol (PAP) by beta-galactosidase (β-gal) in E. coli, reducing Ag⁺ to Ag. Consequently, CTAB-AuNPs remained weak peroxidase activity and could not catalyze the H₂O₂-mediated oxidation of TMB. As the amount of E. coli increased, the absorbance of TMB decreased along with a color change from deep blue to pink. The absorbance intensity displayed a linear dependence on E. coli from 1.0 × 10² to 1.0 × 10⁹ CFU mL^-1. Therefore, the proposed method holds good prospects in foodborne pathogenic bacteria detection.

The fluorescent probe-based recombinase-aided amplification for rapid detection of Escherichia coli O157:H7

Escherichia coli O157:H7 (E. coli O157:H7) is a common foodborne morbigenous microorganism, which can spread through fecal-oral transmission. Humans can be infected by ingesting foods and water contaminated with E. coli O157:H7, which can cause various symptoms. In present study, we have successfully developed a quick and hypersensitive fluorescent probe-based Recombinase-aided amplification (RAA) method and applied in E. coli O157:H7 detection at 39 °C in 20 min. The sensitivity of the assay in pure E. coli O157:H7 suspension was 5.6 × 10⁰ CFU/mL. The fluorescent probe-based RAA assay was further applied in three samples, and the limit of detection (LOD) in skimmed milk, lettuces and lake water was 5.4 × 10¹ CFU/mL, 7.9 × 10¹ CFU/mL and 5.2 × 10¹ CFU/mL, separately. This method showed a high sensitivity and short detection time, which has the feasible application in on-site test in real samples.

Synthesis, Spectroscopic, Thermal and Catalytic Properties of Four New Metal (II) Complexes with Selected N- and O-Donor Ligands

Four solid compounds with formulae: Co(OAc)₂(Im)·H₂O (I), Ni(OAc)₂(Im)_1.5·2H₂O (II), Cu₂(OAc)₄(Im) (III) and Zn(OAc)₂(Im)·H₂O (IV) (where: Im = 1H-Imidazole) were prepared and characterized by chemical and elemental analysis, powder X-ray diffraction patterns and FTIR spectroscopy. Catalytic properties of each complex for styrene oxidation reaction were investigated. Furthermore, thermal properties of compounds were studied using the TG-DTG and DSC techniques under dry air atmosphere. Additionally, volatile thermal decomposition and fragmentation products were also investigated using the TG-FTIR spectra in air.

Rapid polymerase chain reaction assays for Brevibacillus laterosporus detection

The identification of the ubiquitous spore-forming bacterium Brevibacillus laterosporus, whose interest in pharma, agriculture, and other industrial sectors is raising, mostly relies on 16S ribosomal RNA gene sequence analysis. However, due to bacterial gene homology, this method appears insufficient for a proper discrimination of this species, so that the availability of other target genes is necessary. Leveraging the morphological and genetic feature uniqueness of B. laterosporus, a sensitive and reliable detection and quantification method based on polymerase chain reaction (PCR) and quantitative PCR assays, respectively, was developed. Targeting a highly conserved spore surface protein-related gene, B. laterosporus could be easily found in different matrices including soil, food, and insect body. Primer set selectivity was confirmed to be very specific and no false positives or negatives were observed using DNA of different bacterial species as a template. The method developed is also suitable for the rapid identification of newly isolated B. laterosporus strains.