Efficient elimination and detection of phenolic compounds in juice using laccase mimicking nanozymes

Residual phenols in the juice can cause turbidity and affect its sensory quality. Laccase is used to remove phenolic compounds from fruit juices. In order to overcome the shortcomings of natural laccase instability and high cost, in this work, we prepared a laccase mimic enzyme based on copper ion and adenosine monophosphate (AMP-Cu nanozymes). At the same mass concentration (1 mg·ml−1), the catalytic activity of the nanozyme is about 15 times that of laccase. The AMP-Cu nanozymes had a higher Vmax and a lower Km than laccase. The laccase mimic enzyme had a good stability under the condition of 30–90 °C and pH > 6. It also maintained high catalytic activity at high salt concentrations and 9 days storage time. Furthermore, the AMP-Cu nanozymes maintained an initial catalytic activity of about 80% after six consecutive cycles of reaction. The linear range of detection of phenolic compounds by AMP-Cu nanozymes was 0.1–100 μmol·L−1 with a detection limit of 0.033 μmol·L−1. The phenol removal rate of AMP-Cu nanozymes was much higher than that of laccase under different reaction times. When the reaction was performed for 5 h, the phenol removal rate of the fruit juice by AMP-Cu nanozymes was about 65%. The efficient removal of phenolic compounds from different juices by AMP-Cu nanozymes indicates that they have good application prospect in the food juice industry.