Metabolism of l-methionine linked to the biosynthesis of volatile organic sulfur-containing compounds during the submerged fermentation of Tuber melanosporum

Abstract

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.

Chemical diversity of microbial volatiles and their potential for plant growth and productivity

“…Mycelial cultures of T. borchii were found to emit camphor ( Figure 1 ), n -undecane, 2-ethyl-1-butanol, 2-tert-butoxyethanol, 4,5-dimethyl resorcinol, 5-hexen-3-ol, and 3-(methylthio)propanal ( Figure 8 ). Submerged fermentation colures of T. melanosporum were found to emit dimethyl sulfide, dimethyl trisulfide ( Figure 6 ), DMDS, methanethiol, 3-(methylthio)propanal, and 3-(methylthio)-1-propanol ( Figure 8 ; Liu et al, 2013). …”

The Role of the Microbiome of Truffles in Aroma Formation: a Meta-Analysis Approach

“…2). Along with dimethyl disulfide, dimethyl trisulfide, and 3-(methylsulfanyl)propanal, dimethyl sulfide might be derived from the catabolism of methionine through the Ehrlich pathway (36,39,48). According to the mVOC database on microbial volatiles (37), the last four volatiles occur in the fungal classes of Pezizomycetes (i.e., truffles) and Agaricomycetes and in eight bacterial classes (Fig.…”

Current progress on truffle submerged fermentation: a promising alternative to its fruiting bodies

“…a The metabolic pathways of L-methionine to produce 3-(methylthio)propanal; b the typical chromatograms of a truffle fermentation sample after the addition of 5 g L −1 L-methionine; c the typical chromatograms of a truffle fermentation sample without the addition of L-methionine; d the chromatograms of pure 3-(methylthio)propanal (retention time of 15.03 min) and 3-(methylthio)propanol (retention time of 18.69 min). L-methionine (5 g L −1 ) was added at the beginning of fermentation, and the truffle fermentation samples were all harvested on day 3 (Liu et al 2012b(Liu et al , 2013 Regulation of the metabolite biosynthesis through fermentation process control: examples…”

“…The analysis of metabolic pathway of 3-(methylthio) propanal and 3-(methylthio) propanol showed that L-methionine was the key precursor ( Fig. 3a) (Liu et al 2013). Thus, 5 g/L L-methionine was added to the fermentation medium to induce the biosynthesis of 3-(methylthio) propanal and 3-(methylthio) propanol.…”

“…In our present study, more than 12 VOCs were identified as key VOCs for aroma. These compounds are synthesized by more than five biochemical pathways, such as fatty acid catabolism, polyketidic pathways, isoprenoid pathways, nonsulfur amino acid catabolism, and the Ehrlich and demethiolation pathways (Splivallo et al 2007(Splivallo et al , 2011Liu et al 2013). Modeling of genome-scale metabolic and regulatory networks could provide useful information regarding the coregulation of these compounds during high cell density truffle fermentation.…”