A simple visual ethanol biosensor based on alcohol oxidase immobilized onto polyaniline film for halal verification of fermented beverage samples

A simple visual ethanol biosensor based on alcohol oxidase (AOX) immobilised onto polyaniline (PANI) film for halal verification of fermented beverage samples is described. This biosensor responds to ethanol via a colour change from green to blue, due to the enzymatic reaction of ethanol that produces acetaldehyde and hydrogen peroxide, when the latter oxidizes the PANI film. The procedure to obtain this biosensor consists of the immobilization of AOX onto PANI film by adsorption. For the immobilisation, an AOX solution is deposited on the PANI film and left at room temperature until dried (30 min). The biosensor was constructed as a dip stick for visual and simple use. The colour changes of the films have been scanned and analysed using image analysis software (i.e., ImageJ) to study the characteristics of the biosensor's response toward ethanol. The biosensor has a linear response in an ethanol concentration range of 0.01%–0.8%, with a correlation coefficient (r) of 0.996. The limit detection of the biosensor was 0.001%, with reproducibility (RSD) of 1.6% and a life time up to seven weeks when stored at 4 °C. The biosensor provides accurate results for ethanol determination in fermented drinks and was in good agreement with the standard method (gas chromatography) results. Thus, the biosensor could be used as a simple visual method for ethanol determination in fermented beverage samples that can be useful for Muslim community for halal verification.

Biosensors - classification, characterization and new trends

Biosensors represent promising analytical tools applicable in areas such as clinical diagnosis, food industry, environment monitoring and in other fields, where rapid and reliable analyses are needed. Some biosensors were successfully implemented in the commercial sphere, but majority needs to be improved in order to overcome some imperfections. This review covers the basic types, principles, constructions and use of biosensors as well as new trends used for their fabrication.

Real-time quantification of methanol in plants using a hybrid alcohol oxidase-peroxidase biosensor

An amperometric biosensor immobilizing two enzymes and an electron mediator in an identical plane has been fabricated by the self-assembly technique for determination of methanol in crude plant samples. A self-assembled mixed monolayer of 4,4'-dithiodibutyric acid covalently attached two enzymes (Hansenula sp. alcohol oxidase and horseradish peroxidase) and 11-ferrocenyl-1-undecanethiol as an electron mediator on an Au electrode is exploited to produce a two-dimensional reaction matrix. The composition of the two enzymes and electron mediator molecules was optimized for detection of methanol in 0.1 M sodium phosphate buffer (pH 6.0). We successfully quantified methanol in low-purity tobacco (Nicotiana tabacum) plant extracts with the biosensor, which showed sensitivity comparable to that of gas chromatography/mass spectrometry. The redox-relay biosensor is quite simple and stable due to its covalent attachment to the Au surface, making it possible to downsize the construction. We fabricated a miniature methanol biosensor that fitted a well of a 96-well micro assay plate available for high-throughput assay. The biosensor is advantageous for the sensitive, continuous, and convenient determination of methanol.