Biochemical Studies on Oxidation of catechin by Pseudomonas cepasia

我们已经在不同的区域澄清了加热后发酵茶的风味成分。此外，我们还从加热后的发酵茶中分离出了一些微生物。利用这些微生物，考察了它们对风味成分的影响。其中，对影响茶儿茶素的洋葱假单胞菌进行了检测。洋葱假单胞菌是在后加热发酵茶生产过程中从桶前分离出来的。该微生物存在于Goishi-cha(GOS3)中。Laffet-so(PBJ17)和Miang(老挝人民民主共和国B2TS2)。洋葱假单胞菌是一种颗粒阴性杆菌。此外，还对洋葱假单胞菌的特性进行了研究。结果表明，分离的洋葱假单胞菌的生长曲线呈S型，与模式培养相似。分离的洋葱假单胞菌在100℃的热处理条件下仍保持稳定，表现出较高的热稳定性。在最适pH值方面，与模式培养相比，分离的洋葱假单胞菌生长在碱性区域。在模型实验中。将洋葱假单胞菌加入后加热发酵茶生产过程中，监测其风味成分的变化。结果，儿茶素的含量有所下降。尤其是(-)-表没食子儿茶素没食子酸酯((-)-EGCG)显著降低，并对影响儿茶素氧化的酶进行了检测，发现在培养过程中加入儿茶素可降低(-)-EGCG等。研究还表明，降解儿茶素的能力不是存在于洋葱假单胞菌的培养基中，而是存在于细胞中。为了从细胞中提取酶，使用法国压力机破坏细胞是一种有效的方法。还发现儿茶素中的(-)-EGCG是主要底物。

We have clarified flavor components of post heated fermented teas in various are as. Also, we have isolated a number of microorganisms from post-heated fermented teas. By using these microorganisms, effect on flavor components were examined. Among all, Examination was made on Pseudomonas cepasia (P. cepasia) affecting tea catechins. P. cepasia was isolated front a bucket in the process of post-heated fermented tea production . This microorganism was contained in Goishi-cha (GOS3). Laphet-so (PBJ17) and Miang (LAO P.D.R B2TS2). P. cepasia was a grain-negative bactellium. Further, properties of P. cepasia was examined. As a result, the thus isolated P. cepasia showed an S-shape growth curve similar to the type culture . The isolated P. cepasia remained stable even in a heat treatment at 100℃, thus showing a high heat stability. Regarding the optimum pH value, it was found out that this isolated P. cepasia grew in the alkaline region compared with the type culture. In a model experiment . P. cepasia was added in the bucket in the post-heated fermented tea production and changes in the flavor components ware monitored. As a result, the catechin content was decreased. In particular, (-)-epigallocatechin gallate((-)-EGCg) showed a remarkable decrease- Also, examination was made on enzymes seemingly largely affecting the oxidation of catechin- Thus it was found out that (-)-EGCg, etc. were decreased by adding catechin during the culture period. It was also clarified that the capability of degrading catechin appeared not in the P. cepasia culture medium but in the cells. To extract the enzymes from the cells, cell disruption with the use of a French press was an efficacious means . It was also found out that (-)-EGCg, among catechins, served as the major substrate.