Figures & data
Figure 1. Standard curve for polyphenols using guaiacol as standard. The current (mA) was measured by a polyphenol biosensor based on “Nitrocellulose” membrane-bound laccase (purified from Ganoderma sp. by 84.12-fold) at different concentrations of guaiacol as given above.
Figure 2. Scheme of chemical reactions involved in immobilization of laccase onto nitrocellulose membrane.
Figure 3. SEM of nitrocellulose membrane (a) without enzyme at 158X and (b) with immobilized enzyme at 158X.
Figure 4. Cyclic voltammetric (CV) curves of modified membrane biosensor (a) without and (b) with addition of 0.1 ml guaiacol solution (10 μM). Supporting electrolyte: 1M KCl solution; scan rate: 50 mVs−1.
Figure 5. Effect of pH on response of polyphenol biosensor-based nitrocellulose membrane-bound laccase.
Figure 6. Effect of temperature on response of polyphenol biosensor based on nitrocellulose membrane-bound laccase.
Figure 7. Effect of substrate concentration on response of polyphenol biosensor based on nitrocellulose membrane-bound laccase.
Figure 8. Lineweaver-Burk plot for effect of guaiacol concentration on response of the polyphenol biosensor based on nitrocellulose membrane-bound enzyme.
Table 1. Analytical recovery of added guaiacol in the grape juice, as measured by polyphenol biosensor based on nitrocellulose membrane-bound laccase.
Table 2. Within and between assay coefficients of variation (CV) for determination of total phenolic content in the grape juice sample as measured by polyphenol biosensor based on nitrocellulose membrane-bound laccase.
Figure 9. Storage stability of laccase electrode in a reaction buffer at 4–8°C.
Table 3. A comparison of various analytical and kinetic properties of polyphenol biosensors based on laccase immobilized on different supports.
Table 4. Total phenolic content in different brands of fruit juices and alcoholic beverages as measured by polyphenol biosensor based on nitrocellulose membrane-bound laccase.
