Biochemical Studies on Oxidation of catechin by Pseudomonas cepasia

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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.