Leangnim Nalapat, Aisara Jakkrit, Unban Kridsada, Khanongnuch Chartchai, Kanpiengjai Apinun
Graduate Program in Biotechnology, The Graduate School, Chiang Mai University, Chiang Mai 50200, Thailand.
Department of Chemistry, Division of Biochemistry and Biochemical Technology, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand.
Microorganisms. 2021 Jun 30;9(7):1418. doi: 10.3390/microorganisms9071418.
Previously, nine tannin-tolerant and tannase-producing yeasts were isolated from Miang; all produced cell-associated tannase (CAT) during growth in tannin substrate. Among which, only CAT from showed better stability than its purified form. Yet, it is of particular interest to directly characterize CATs from the latter yeasts. In this study, four CATs from yeasts, namely A22.3, sp. A39.3, A45.1, and A45.3 were characterized. The results indicate that all CATs were produced within the same production yield (11 mU/mL). Most CATs exhibited similar pH and temperature optima and stabilities, except for CAT from A22.3. This CAT was assigned as acid-stable tannase due to its unusual optimum pH of 2.0 with pH stability and half-life thermostability in the range of pH 2.0-4.0, and 70 °C, respectively. All CATs demonstrated high substrate specificity toward epigallocatechin gallate and epicatechin gallate, thus forming epigallocatechin and epicatechin, respectively. Moreover, they showed operational stability to repeated use for up to five cycles without loss of the initial activity. Therefore, CATs from these yeasts could be useful for the extraction and biotransformation of tea catechins and related applications.
此前，从米昂中分离出9株耐单宁且产单宁酶的酵母；所有菌株在单宁底物中生长时均产生细胞相关单宁酶（CAT）。其中，只有来自[具体菌株名称未给出]的CAT比其纯化形式表现出更好的稳定性。然而，直接表征后几种酵母的CATs特别有趣。在本研究中，对来自酵母的四种CATs进行了表征，即[具体酵母名称未给出]A22.3、[具体酵母名称未给出]sp. A39.3、[具体酵母名称未给出]A45.1和[具体酵母名称未给出]A45.3。结果表明，所有CATs的产量相同（11 mU/mL）。除了来自[具体酵母名称未给出]A22.3的CAT外，大多数CATs表现出相似的最适pH值、温度以及稳定性。由于其异常的最适pH值为2.0，在pH 2.0 - 4.0范围内具有pH稳定性，在70°C下具有半衰期热稳定性，这种CAT被归类为酸稳定单宁酶。所有CATs对表没食子儿茶素没食子酸酯和表儿茶素没食子酸酯均表现出高底物特异性，分别形成表没食子儿茶素和表儿茶素。此外，它们在重复使用多达五个循环时表现出操作稳定性，且初始活性没有损失。因此，来自这些酵母的CATs可用于茶儿茶素的提取和生物转化以及相关应用。
