Lee Yeonhee, Lin Zhi, Du Guocheng, Deng Zhuangmei, Yang Haiquan, Bai Wenxiang
Key Laboratory of Tea Biology and Resource Utilization, Ministry of Agriculture, Chinese Academy of Agricultural Sciences, 9 Meiling South Road, Hangzhou, Zhejiang 310008, China.
Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Road, Wuxi 214122, China.
J Sci Food Agric. 2015 Oct;95(13):2686-92. doi: 10.1002/jsfa.7003. Epub 2014 Dec 4.
Fungal laccase (EC 1.10.3.2) is an important enzyme for catalyzing the oxidation of tea polyphenols during the fermentation of tea. (-)-Epigallocatechin gallate (EGCG) is the main ingredient of tea polyphenols. To a certain extent, the oxidation degree of EGCG reflects the fermentation degree of tea. This study preliminarily optimized the conditions for catalytically oxidizing EGCG by Aspergillus sp. trijbl1112 laccase and systematically analyzed the components and contents of the EGCG oxidation products.
Aspergillus sp. trijbl1112 laccase oxidized EGCG into free catechins, ester catechins, gallic acid and tea pigments. The reaction conditions had a significant impact on the oxidation rate, types and concentrations of the products. At natural pH, 69.29% of EGCG was oxidized when 1 mL of EGCG (1 mmol L(-1) ) was catalyzed by 10 µg of fungal laccase for 150 min at 70 °C. When the EGCG oxidation rate was 69.27%, free catechins ((+)-catechin and (-)-epigallocatechin) and tea pigments (mainly thearubigin and theabrownin) constituted 48.42 and 38.87% of the oxidation products respectively.
The results may provide a theoretical basis for the application of EGCG oxidation using laccase and provide a novel technique for obtaining high production of tea pigments.
真菌漆酶（EC 1.10.3.2）是茶叶发酵过程中催化茶多酚氧化的一种重要酶。（-）-表没食子儿茶素没食子酸酯（EGCG）是茶多酚的主要成分。EGCG的氧化程度在一定程度上反映了茶叶的发酵程度。本研究初步优化了曲霉属trijbl1112漆酶催化氧化EGCG的条件，并系统分析了EGCG氧化产物的成分和含量。
曲霉属trijbl1112漆酶将EGCG氧化为游离儿茶素、酯型儿茶素、没食子酸和茶色素。反应条件对产物的氧化速率、种类和浓度有显著影响。在自然pH值下，70℃时，10μg真菌漆酶催化1 mL EGCG（1 mmol L⁻¹）150 min，69.29%的EGCG被氧化。当EGCG氧化率为69.27%时，游离儿茶素（（+）-儿茶素和（-）-表没食子儿茶素）和茶色素（主要是茶红素和茶褐素）分别占氧化产物的48.42%和38.87%。
该结果可为漆酶氧化EGCG的应用提供理论依据，并为获得高产茶色素提供新技术。
