Fast Electrochemical Measurement of Laccase Activity for Monitoring Grapes’ Infection with Botrytis cinerea

Grapes’ infection with the fungi Botrytis cinerea is one of the major causes of economic loss in the winemaking sector worldwide. The laccase activity of grapes is considered an appropriate indicator of this type of fungal infection, and enzymatic activity higher than 3 U/mL indicates a high risk of irreversibly damaged grape must due to enzymatic browning. This work describes a fast test for the measurement of laccase activity based on a dual optical and electrochemical detection method. A paper sensor impregnated with the enzymatic substrate dye 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) provides a semi-quantitative optical measurement. While the paper sensor can be used independently, when combined with a screen-printed electrode and amperometry measurements, it enables the quantitative detection of laccase activities down to 0.4 U/mL in only 5 min. The method was applied for monitoring the artificial infection of white, rosé, and red grapes with different strains of Botrytis cinerea. The results were confirmed by parallel analysis using the spectrophotometric method of laccase activity determination based on syringaldazine. The influence of the fungal strain and type of grape on laccase activity levels is reported. The demonstrated robustness, simplicity, and versatility of the developed method make it ideal for application on-site in the vineyard or at grape processing points.Financial support provided by the Romanian Executive Agency for Higher Education, Research, Development and Innovation (UEFISCDI), ERANET-MANUNET-III-WINBIOTOOL-2, contract 151/9.03.2020 grant (for A.V), contract150/9.03.2020 (for P.E) and contract 152/9.03.2020 (for C.P. (Catalina Pantazi), E.B., and M.I.); the Romanian Academy grant RO1567-IBB05/2021 (for R.R. and C.P. (Cristina Purcarea)); the Basque Government and the European Union through the European regional development fund 2014–2020 (FEDER) (ZL-2020/00532 and ZL-2021/00340); and the Diputación Foral de Álava (ALAVA INNOVA program—INNOEM-2020/00045) for Bodegas de los Herederos del Marqués de Riscal; and the Diputación Foral de Álava (ALAVA INNOVA program— INNOEM-2020/00045) for Bodegas de los Herederos del Marqués de Risca is gratefully acknowledged

Achievements and Prospects in Electrochemical-Based Biosensing Platforms for Aflatoxin M1 Detection in Milk and Dairy Products

Aflatoxins, which are mainly produced by Aspergillus flavus and parasiticus growing on plants and products stored under inappropriate conditions, represent the most studied group of mycotoxins. Contamination of human and animal milk with aflatoxin M1, the hydroxylated metabolite of aflatoxin B1, is an important health risk factor due to its carcinogenicity and mutagenicity. Due to the low concentration of this aflatoxin in milk and milk products, the analytical methods used for its quantification have to be highly sensitive, specific and simple. This paper presents an overview of the analytical methods, especially of the electrochemical immunosensors and aptasensors, used for determination of aflatoxin M1

Progress in Electrochemical (Bio)Sensors for Monitoring Wine Production

Electrochemical sensors and biosensors have been proposed as fast and cost effective analytical tools, meeting the robustness and performance requirements for industrial process monitoring. In wine production, electrochemical biosensors have proven useful for monitoring critical parameters related to alcoholic fermentation (AF), malolactic fermentation (MLF), determining the impact of the various technological steps and treatments on wine quality, or assessing the differences due to wine age, grape variety, vineyard or geographical region. This review summarizes the current information on the voltamperometric biosensors developed for monitoring wine production with a focus on sensing concepts tested in industry-like settings and on the main quality parameters such as glucose, alcohol, malic and lactic acids, phenolic compounds and allergens. Recent progress featuring nanomaterial-enabled enhancement of sensor performance and applications based on screen-printed electrodes is emphasized. A case study presents the monitoring of alcoholic fermentation based on commercial biosensors adapted with minimal method development for the detection of glucose and phenolic compounds in wine and included in an automated monitoring system. The current challenges and perspectives for the wider application of electrochemical sensors in monitoring industrial processes such as wine production are discussed

Nanocomposites Based Electrosensitive Platforms for Nitrite and Biogenic Amines Determination

Highly electrosensitive platforms have been developed using different nanocomposite materials based on carbon allotropes and different metallic nanoparticles for determination of nitrite and biogenic amines (BAs). The nitrification process occurred in soil represents an important source of pollution. The nitrification consists in biological oxidation of the relatively immobile ammonium (NH4+) to highly mobile nitrate, via nitrite. This process is carried out mainly by the ammonia–oxidizing bacteria (Nitrosomonas sp. and Nitrobacter sp.) present in the soil microbial population [1,2]. The nitrite contamination of ground and surface waters represents the major concern associated with the nitrification process. Additionally, the growing needs for food and environmental safety has led to an increase in research for the detection of biogenic amines (BAs) in recent years. Despite the fact that BAs are increasingly present in food and beverages, causing toxic effects in the body, legislation that limits their presence in food chains needs to be updated, thus requiring sensitive tools for their detection [3,4]. Miniaturized analytical tools have been developed based on nanocomposite materials obtained through combination of different carbon allotrope materials (nanoribbons, nanotubes—single and multiwalled—and nanofibers) with metallic nanoparticles (Ag, Au-Ag, Pt, Cu). Thus, carbon based screen-printed electrodes (SPE) were chemically modified with the obtained nanocomposite materials and further characterized using different electrochemical techniques. In order to allow a selective and sensitive determination of analytes, an electropolymerized film was deposed on the modified sensors. For BAs determination were realized with two configurations of biosensors, a bienzymatic one consisting in immobilization of diamine oxidase (DAO) and horseradish peroxidase (HRP) onto the modified sensors, and, respectively, a mono-enzymatic system based on immobilization of DAO onto the modified sensors. It was taken into account that the charge of carbon-based nanomaterials on the surface of the sensors should not exceed 5%, in order to ensure a low based current. Morpho-structural and electrochemical characterization studies of the modified SPEs have been performed in order to achieve a high sensitivity and selectivity of detection, applying a low overvoltage. The co-polymeric film ensured a better stability of the nanocomposite material layers at the electrode surface and an optimal matrix for enzymes immobilization. Optimization of the nanocomposite-based sensors were performed, and finally detection of biogenic amines was carried out using biosensors based on single-walled carbon nanotubes and Pt nanoparticles, while nitrite determination was performed using multi-walled carbon nanotubes and AgNP modified sensors at applied potentials between −0.45 and +0.6 V vs. Ag/AgCL. The developed sensors and biosensors showed good sensitivities of nitrite and BAs detection. Although the enzyme DAO has a low enough activity to catalyze the oxidation of amine of interest, the detection limits were lowered due to the electrocatalytic activity of nanocomposite materials and the HRP enzyme used

Hybrid Inkjet-Printable Paste for Screen-Printed Electrodes

Nowadays, Gram-negative bacteria (GNB) are among the most significant public health and environment concerns in the world due to their high resistance to antibiotics [...