Biosensors for d-Amino Acid Detection
The presence of d-amino acids in foods is promoted by harsh technological processes (e.g., high temperature or extreme pH values) or can be the consequence of adulteration or microbial contamination (d-amino acids are major components of the bacterial cell wall). For this reason, quality control is becoming more and more important both for the industry (as a cost factor) and for consumer protection. For routine food analysis and quality control, simple and easily applicable analytical methods are needed: biosensors can often satisfy these requirements. The use of an enzymatic, stereospecific reaction could confer selectivity to a biosensor for detecting and quantifying d-amino acids in foodstuffs. The flavoenzyme d-amino acid oxidase from the yeast Rhodotorula gracilis is an ideal biocatalyst for this kind of application because of its absolute stereospecificity, very high turnover number with various substrates, tight binding with the FAD cofactor, and broad substrate specificity.
Furthermore, alterations in the local brain concentrations of d-serine (predominantly d-amino acid in the mammalian central nervous system) have been related to several neurological and psychiatric diseases. Therefore, quantifying this neuromodulator represents an important task in biological, medical, and pharmaceutical research. Recently, an enzymatic microbiosensor, also using R. gracilis d-amino acid oxidase as biocatalyst, was developed for detecting d-serine in vivo.
Key wordsAmperometric detection d-Amino acid oxidase d-Serine Food quality Analytical detection
The work reported in this paper was supported by grants from Fondo di Ateneo per la Ricerca (University of Insubria) to S. Sacchi and L. Pollegioni and from Fondazione Cariplo and Regione Lombardia (bando Cooperazioni Scientifiche Internazionali) to L. Pollegioni. We thank Carlo Rossetti, Jean-Pierre Mothet, and Stéphane Marinesco who over the years have actively contributed to the evolution of DAAO-based biosensors.
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