| Summary: | 碩士 === 國立屏東科技大學 === 食品科學系所 === 96 === A popcorn-like flavor compound, 2-acetyl-1-pyrroline (2-AP), has been reported as a potent flavor component of an aromatic rice, taro, pandan and bread. The nitrogen source of pyrroline of 2-AP was proline, but the acetyl-group has not been well-characterized. On the other hand, methylglyoxal(MG), the putative precursor of 2-AP may derive from dihydroxyacetone phosphate (DHAP) through triosephosphate isomerase catalysis. It was hypothesized that 2-AP was synthesized from △1-Pyrroline-5- Carboxylate (P5C) and Methylglyoxal (MG). Therefore, in order to study the molecular mechanism of 2-AP biosynthesis, we analyzed the expression profile of MG and P5C biosynthetic enzymes and the level of MG and P5C in Bacillus subtilis var. natto under salt stress. The results showed that the level of glycerol-3-phosphate dehydrogenase (G3PDH), triosephosphate isomerase (TIM), fructose-1,6-bisphosphate aldolase (FBA), methylglyoxal synthase (MGS), Ornithne aminotransferase (OAT), proline dehydrogenase (PDH), γ-Glutamyl kinase (γ-GK) and γ-Glutamyl phosphate reductase (γ-GPR) mRNA increased significantly after 30 min of exposure at
various concentration of NaCl. Otherwise, the concentrations of MG and P5C increased with increasing NaCl concentration, and when cell were subjected to 1M NaCl treatment for 20 min, accumulation of MG and P5C were reached highest (about 91.5 μmolg-1 and 0.102 μmolg-1). In vitro model system was set up to study the formation of 2-AP under salt stress. The qualitative analysis of 2-AP was performed by GC-MS. Total ion chromatogram showed the peak with retention time at 7.45 minutes corresponds to 2-AP. Therefore, we purposed MG interact with P5C to produce 2-AP.
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