The Sonogel–Carbon materials as basis for development of enzyme biosensors for phenols and polyphenols monitoring: A detailed comparative study of three immobilization matrixes

Current State of Sensors and Sensing Systems Utilized in Beer Analysis

Beer is one of the most consumed beverages in the world. Advances in instrumental techniques have allowed the analysis and characterization of a large number of beers. However, review studies that outline the methodologies used in beer characterization are scarce. Herein, a systematic review investigating the molecular targets and sensometric techniques in beer characterization was performed following the PRISMA protocol. The study reviewed 270 articles related to beer analysis in order to provide a comprehensive summary of the recent advances in beer analysis, including methods using sensors and sensing systems. The results revealed the use of various techniques that include several technologies, such as nanotechnology and electronics, often combined with scientific data analysis tools. To our knowledge, this study is the first of its kind and provides the reader with a faithful overview of what has been done in the sensor field regarding beer characterization.

Fast and direct amperometric analysis of polyphenols in beers using tyrosinase-modified screen-printed gold nanoparticles biosensors

In this work it is explored a real applicability of miniaturised and portable biosensing technology for the estimation of total phenolic content in 15 different commercial beers by applying direct amperometry. Gold nanoparticles screen-printed electrodes were thoroughly modified with tyrosinase (Tyr-AuNPS-SPCEs), which was immobilised on the surface by crosslinking with glutaraldehyde. All chemical and instrumental variables involved in the electrochemical method were optimised to develop a reliable and powerful tool to estimate rapidly the content of phenolic compounds in complex beer samples. Catechol, phenol, caffeic acid and tyrosol were analysed individually using the proposed methodology and good analytical and kinetic performances were obtained. Total phenolic content in tested beers (high fermented, low fermented and non-alcoholic) were expressed as mg L^-1 of tyrosol, which is one of the major phenolic compound reported in beer. Moreover, the developed amperometric methodology was successfully benchmarked against standardised Folin-Ciocalteau spectrophotometric method with a good Pearson correlation (r = 0.821, p < 0.01). Hierarchical Cluster Analysis (HCA) was also applied on electrochemical results and a good capability to group tested beers based on their tyrosol concentration was demonstrated.

Low-frequency ultrasound in biotechnology: state of the art

The use of low-frequency (10-60 kHz) ultrasound for enhancement of various biotechnological processes has received increased attention over the last decade as a rapid and reagentless method. Recent breakthroughs in sonochemistry have made the ultrasound irradiation procedure more feasible for a broader range of applications. By varying the sonication parameters, various physical, chemical and biological effects can be achieved that can enhance the target processes in accordance with the applied conditions. However, the conditions that have provided beneficial effects of ultrasound on bioprocesses are case-specific and are therefore not widely available in the literature. This review summarizes the current state of the art in areas where sonochemistry could be successfully combined with biotechnology with the aim of enhancing the efficiency of bioprocesses, including biofuel production, bioprocess monitoring, enzyme biocatalysts, biosensors and biosludge treatment.

(Bio)Sensor Approach in the Evaluation of Polyphenols in Vegetal Matrices

Polyphenols are compounds widely distributed in the plant kingdom and have attracted much attention, because of their health benefits and important properties such as radical scavenging, metal chelating agents, inhibitors of lipoprotein oxidation, anti-inflammatory and anti-allergic activities. Due to their important role in the diet and in therapy, it is important to estimate their content in the different matrices of interest. Besides classical analytical methods, new emerging technologies have also appeared in the last decade aiming for simple and eventually cheap detection of polyphenols. This review focused on the recent applications of biosensing-based technologies for polyphenol estimation in vegetal matrices, using different transduction principles. These analytical tools are generally fast, giving responses in the order of a few seconds/minutes, and also very sensitive and generally selective (mainly depending on the enzyme used). Direct measurements in most of the investigated matrices were possible, both in aqueous and organic phases.

A comparison of three amperometric phenoloxidase-Sonogel-Carbon based biosensors for determination of polyphenols in beers

Three phenoloxidases based biosensors were successfully developed using as electrochemical transducer a new type of electrode recently developed by our group: the "Sonogel-Carbon electrode". The employed enzymes were Trametes versicolor laccase (Lac), Mushroom tyrosinase (Tyr), and Horseradish peroxidase (HRP). Immobilization step was accomplished by doping the electrode surface with a mixture of the individual enzyme and Nafion ion exchanger as additive-protective. The biosensor responses, optimized in beer real samples, were evaluated for five individual polyphenols. It was found that the developed biosensors were sensitive to nanomolar concentrations of the tested polyphenols. As example, the limit of detection, sensitivity, and response linear range for caffeic acid for Nafion-Lac/Sonogel-Carbon biosensor were 0.06μmolL(-1), 99.6nAμmol(-1)L, and 0.04-2μmolL(-1), respectively. The stability and reproducibility of the biosensors were evaluated by applying them directly to beer real samples. It has been demonstrated that the Nafion-Lac/Sonogel-Carbon system is the more stable with a relative standard deviation of 3.3% (n=10), maintaining 84% of its stable response for at least three weeks. Estimation of polyphenol index in eight lager beers and a comparison of the results with those obtained by a classical method was carried out.

Titania sol-gel-derived tyrosinase-based amperometric biosensor for determination of phenolic compounds in water samples. Examination of interference effects

For detection of phenolic compounds in environmental water samples we propose an amperometric biosensor based on tyrosinase immobilized in titania sol-gel. The analytical characteristics toward catechol, p-cresol, phenol, p-chlorophenol, and p-methylcatechol were determined. The linear range for catechol determination was 2.2 x 10(-7)-1.3 x 10(-5) mol L(-1) with a limit of detection of 9 x 10(-8) mol L(-1) and sensitivity 2.0 x 10(3) mA mol(-1) L. The influence of sample matrix components on the electrode response was studied according to Plackett-Burman experimental design. The potential interferents Mg(2+), Ca(2+), HCO3(-), SO4(2-), and Cl(-), which are usually encountered in waters, were taken into account in the examination. Cu(2+) was also taken into account, because CuSO(4) is sometimes added to a water sample, as a preservative, before determination of phenolic compounds. It was found that among the ions tested only Mg(2+) and Ca(2+) did not directly affect the electrode response. The developed biosensor was used for determination of catechol in spring and surface water samples using the standard addition method.

Dual laccase-tyrosinase based Sonogel-Carbon biosensor for monitoring polyphenols in beers

A biosensor based on the bi-immobilization of laccase and tyrosinase phenoloxidase enzymes has been successfully developed. This biosensor employs as the electrochemical transducer the Sonogel-Carbon, a novel type of electrode developed by our group. The immobilization step was accomplished by doping the electrode surface with a mixture of the enzymes, glutaricdialdehyde, and Nafion-ion exchanger, as protective additive. The response of this biosensor, denoted the dual Trametes versicolor laccase (La) and Mushroom tyrosinase (Ty) based Sonogel-Carbon, was optimized directly in beer real samples and its analytical performance with respect to five individual polyphenols was evaluated. The Lac-Ty/Sonogel-Carbon electrode responds to nanomolar concentrations of flavan-3-ols, hydroxycinnamic acids, and hydroxybenzoic acids. The limit of detection, sensitivity, and linear range for caffeic acid, taken as an example, were 26 nM, 167.53 nA M (-1), and 0.01-2 microM, respectively. In addition, the stability and reproducibility of the biosensor were also evaluated in beer samples. The Lac-Ty/sonogel-carbon electrode was verified as very stable in this matrix, maintaining 80% of its stable response for at least three weeks, with a RSD of 3.6% ( n = 10). The biosensor was applied to estimate the total polyphenol index in ten beer samples, and a correlation of 0.99 was obtained when the results were compared with those obtained using the Folin-Ciocalteau reagent.