A new galacturonic acid biosensor based on a recombinant uronate dehydrogenase enzyme from Pseudomonas Syringae

D-Galacturonic acid is a sugar acid, an oxidized form of D-galactose. It is the main component of pectin, a natural polymer that exists in primary cell walls of terrestrian plants. D-Galacturonic acid as well as other sugar acids such as D-gluconic and D-glucuronic acids are associated with grape infection by B. Cinerea . They are characteristic of the disease and therefore their presence has been used as an indicator of the degree of infection. None of these sugar acids affects taste or odor of wine. However, D-galacturonic acid may be involved in the browning of white wines, a process of continuous oxidation which can cause loss of aromatic freshness and, in the final stages, the appearance of precipitates of condensed phenolic material in the bottled wine. The determination of D-galacturonic acid is therefore of particular interest in wine production. Food control analyses require robust, sensitive, and selective detection methods. The most commonly used methods such as chromatography and mass spectrometry require expensive instrumentations and skilled technicians. Enzyme biosensors are a good alternative because they incorporate robustness and selectivity to low cost of equipment and easiness of sample preparation. In this work a new biosensor for D-galacturonic acid detection has been assembled by using a carbon screen printed electrode modified by depositing a solution of photocrosslinkable PVA-SbQ containing appropriate amounts of uronate dehydrogenase from Agrobacterium tumefaciens and diaphorase from Clostridium kluverii enzymes. The optimized biosensor showed a good linear range (8.5-43 mg/L), a good reproducibility (2.0%, n=6) and a good stability. The proposed biosensor was successively applied for the determination of D-galacturonic acid in different samples of wine.