Search

Tuber melanosporum, known as the black diamond of cuisine, is highly appreciated for its unique and characteristic aroma, which is mainly due to its volatile organic sulfur-containing compounds (VOSCs). In this work, by adding 5 g/L  l-methionine to the fermentation medium, the activities of aminotransferase and α-ketoacid decarboxylase were significantly enhanced by 103 and 250 %, respectively, while the activities of alcohol dehydrogenase and demethiolase were decreased by 277 and 39 %. Then, the six VOSCs, i.e., methanethiol (MTL), dimethyl sulfide (DMS), dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), 3-(methylthio)propanal (methional), and 3-(methylthio)-1-propanol (methionol), were first detected in the submerged fermentation of T. melanosporum. These results indicated that the biosynthesis of VOSCs was triggered by aminotransferase and α-ketoacid decarboxylase. The production of methional and methionol increased with the increased concentrations of l-methionine (i.e., 5, 10, 15, and 20 g/L) before day 4 of the culture protocol, and methionol was the major product in the Ehrlich pathway. The production of MTL was significantly decreased after day 4 with a significantly increased DMDS, and DMDS was the major product of the demethiolation pathway. Compared with the demethiolation pathway with a total flux of sulfur of 11.33–24.32 μM, the Ehrlich pathway with a total flux of sulfur of 6,149–10,330 μM was considered the major pathway for the biosynthesis of VOSCs. This is the first report linking the metabolism of l-methionine to the biosynthesis of VOSCs by the Ehrlich and demethiolation pathways during the submerged fermentation of T. melanosporum. [ABSTRACT FROM AUTHOR]

Tuber melanosporum, known as the black diamond of cuisine, is highly appreciated for its unique and characteristic aroma, which is mainly due to its volatile organic sulfur-containing compounds (VOSCs). In this work, by adding 5 g/L  l-methionine to the fermentation medium, the activities of aminotransferase and α-ketoacid decarboxylase were significantly enhanced by 103 and 250 %, respectively, while the activities of alcohol dehydrogenase and demethiolase were decreased by 277 and 39 %. Then, the six VOSCs, i.e., methanethiol (MTL), dimethyl sulfide (DMS), dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), 3-(methylthio)propanal (methional), and 3-(methylthio)-1-propanol (methionol), were first detected in the submerged fermentation of T. melanosporum. These results indicated that the biosynthesis of VOSCs was triggered by aminotransferase and α-ketoacid decarboxylase. The production of methional and methionol increased with the increased concentrations of l-methionine (i.e., 5, 10, 15, and 20 g/L) before day 4 of the culture protocol, and methionol was the major product in the Ehrlich pathway. The production of MTL was significantly decreased after day 4 with a significantly increased DMDS, and DMDS was the major product of the demethiolation pathway. Compared with the demethiolation pathway with a total flux of sulfur of 11.33–24.32 μM, the Ehrlich pathway with a total flux of sulfur of 6,149–10,330 μM was considered the major pathway for the biosynthesis of VOSCs. This is the first report linking the metabolism of l-methionine to the biosynthesis of VOSCs by the Ehrlich and demethiolation pathways during the submerged fermentation of T. melanosporum. [ABSTRACT FROM AUTHOR]

Uniform design and partial least squares regression were adopted to quantitatively analyze the effects of plant oil and fatty acid as well as their addition amount and addition time on the performance of Tuber melanosporum submerged fermentation. The regression models showed the optimal scheme was the addition of 1.2 mL soybean oil on day 9, which was validated by experiment. The maximal biomass of 25.89 ± 1.01 g/L and extracellular polysaccharides (EPS) production of 6.51 ± 0.68 g/L were obtained, which were enhanced by 18.5% and 86%, respectively. Palmitic acid was identified to be the key component to stimulate the cell growth and EPS biosynthesis, and stearic acid was beneficial for the production of intracellular polysaccharides. Not only the biomass but also EPS production obtained in this work are the highest reported in the batch fermentation of truffle. [ABSTRACT FROM AUTHOR]