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Tannase is widely used in tea beverage processing because of its ability to catalyze the hydrolysis of hydrolysable tannins or gallic acid esters and effectively improve the quality of tea extracts through enzymatic extraction. A new thermophilic tannase was cloned from Aspergillus niger FJ0118 and characterized. The tannase exhibited an optimal reaction temperature of 80 °C and retained 89.6% of the initial activity after incubation at 60 °C for 2 h. The enzymatic extraction of green tea at high temperature (70 °C) for a short time (40 min) was devised on the basis of the superior thermal stability of tannase. The enzymatic reaction significantly increased the total polyphenol content of green tea extract from 137 g·kg−1 to 291 g·kg−1. The enzymatic reaction effectively degraded the ester catechins into non-ester catechins compared with the water extraction method. Results suggested that the thermally stable tannase exhibited potential applications in the enzymatic extraction of green tea beverage. [ABSTRACT FROM AUTHOR]

The pods of Caesalpinia spinosa consists of gallotannins, which represent more than 50 % of its weight. The traditional chemical procedure used to produce gallic acid (GA) from tara gallotannins is a high-pollution process. Although biological procedures, including microbial fermentation and enzymatic hydrolysis, are environmentally friendly, insufficient production efficiency significantly hinders industrial application. In this study, we proposed a novel strategy for the simultaneous extraction and enzymatic hydrolysis of tara gallotannins with intermittent feeding. A recombinant thermostable tannase (Tan1) derived from Aspergillus oryzae was first constructed to adapt to the high-temperature simultaneous extraction and enzymatic hydrolysis process. Tan1 showed competent activity yield (83.11 U/mL) and excellent heat resistance, exhibiting the highest activity at 80 °C and half-lives at 60 °C for more than 6 h. The production efficiencies of GA using different enzymatic hydrolysis strategies were compared. The simultaneous extraction and enzymatic hydrolysis strategy combined with intermittent feeding minimized the inhibition of tara gallotannins on Tan1 activity and resulted in an increased GA yield. Using this strategy, 192 g/L tara powder (intermittent feed for 6 times) was treated with Tan1 at 60 °C for 177 min, resulting in 78.5 g/L GA output which was the highest among the currently reported values obtained using biological protocols for GA production. • A thermal stable tannase with high activity was successfully expressed in Pichia pastoris. • A novel strategy was proposed to minimize inhibition effect of tannic acid on tannase. • Highest yield was obtained among biological approaches for gallic acid production. [ABSTRACT FROM AUTHOR]