Elemental iron protects gut microbiota against oxygen-induced dysbiosis.

Gut dysbiosis induced by oxygen and reactive oxygen species may be related to the development of inflammation, resulting in metabolic syndrome and associated-conditions in the gut. Here we show that elemental iron can serve as an antioxidant and reverse the oxygen-induced dysbiosis. Fecal samples from three healthy donors were fermented with elemental iron and/or oxygen. 16S rRNA analysis revealed that elemental iron reversed the oxygen-induced disruption of Shannon index diversity of the gut microbiota.The bacteria lacking enzymatic antioxidant systems also increased after iron treatment. Inter-individual differences, which corresponded to iron oxidation patterns, were observed for the tested donors. Gut bacteria responding to oxygen and iron treatments were identified as guilds, among which, Escherichia-Shigella was promoted by oxygen and depressed by elemental iron, while changes in bacteria such as Bifidobacterium, Blautia, Eubacterium, Ruminococcaceae, Flavonifractor, Oscillibacter, and Lachnospiraceae were reversed by elemental iron after oxygen treatment. Short-chain fatty acid production was inhibited by oxygen and this effect was partially reversed by elemental iron. These results suggested that elemental iron can regulate the oxygen/ROS state and protect the gut microbiota from oxidative stress.

Fermentation Dynamics and Benzylic Derivative Production in Ischnoderma resinosum Isolates.

Fermentation dynamics and benzylic derivative production were evaluated in the fermentation broth of six different Ischnoderma resinosum (P. Karst) isolates over a period of 30 days to understand their potential applications in bioreactor optimization for natural flavor compound production. d-Glucose and d-fructose levels decreased from 20.4 ± 0.4 to 7.1 ± 1.4 g/L and 1.0 ± 0.1 to <0.1 g/L, respectively, in all fermentations. Isolate I2 produced the highest concentration of ethanol (546. 4 ± 0.4 mg/L). l-Lactic acid production varied between 4.3 ± 0.6 and 3.7 ± 0.2 mg/L, whereas acetic acid concentrations decreased from 81.0 ± 3.3 to <40.0 mg/L. pH decreased from 4.9 ± 0.0 to 3.6 ± 0.4 at the end of 30 days in all fermentations. Isolate I3 was the highest producer of benzaldehyde (BA) (12.0 ± 0.2 mg/kg) and 4-methoxybenzaldehyde (4-MBA) (239.6 ± 3.9 mg/kg), while isolate I4 was the highest producer of 3,4-dimethoxybenzaldehyde (3,4-DMBA) (27.8 ± 0.2 mg/18 kg). Identification of isolate I3 as a high BA and 4-MBA producer and isolate I4 as a high 3,4-DMBA producer suggested differential benzylic derivative production among I. resinosum isolates. This study lays the foundation for future investigations evaluating additional I. resinosum isolates for benzylic derivative production as well as studies aimed at bioreactor optimization with potential commercial application.

Key Odorants from the Fragrant Bolete, Suillus punctipes.

The fragrant bolete, Suillus punctipes (Peck) Singer, is an edible mushroom with a unique aroma reminiscent of mushroom and citrus peel with an undertone of apricot. Thirty-five odorants were identified using solvent-assisted flavor evaporation (SAFE) and aroma extract dilution analysis (AEDA). Fourteen odorants including those with flavor dilution (FD) factors ≥64 were quantitated using stable isotope dilution assays (SIDA). Some odorants with high OAVs included 1-octen-3-one (OAV 164368), 1-octen-3-ol (OAV 3421), linalool (OAV 812), and nonanal (OAV 487). An odor simulation model was prepared closely matching the aroma of the mushroom. Omissions experiments revealed that 1-octen-3-one, 1-octen-3-ol, (2E)-oct-2-enal, linalool, δ-dodecalactone, and a mixture of three aldehydes, octanal, nonanal, and decanal, were essential odorants for the aroma profile. Enantiomeric ratios were determined for several odorants employing chiral chromatography. The results from this study lay the groundwork for future studies in the aroma chemistry of S. punctipes and other mushrooms from the Suillus genus.

Biosynthesis of Benzylic Derivatives in the Fermentation Broth of the Edible Mushroom, Ischnoderma resinosum.

Employing isotope incubation studies, the biosynthetic pathway leading to a series of benzylic derivatives was elucidated in the fermentation broth of the edible mushroom Ischnoderma resinosum (P. Karst). Twenty-six hydroxy- and methoxy- benzylic derivatives were screened by gas chromatography-mass spectrometry (GC-MS) of which 13 were detected in the culture media. Results from the isotope incubation studies showed the transformation of both benzyl alcohol and benzoic acid into benzaldehyde. Benzaldehyde was then converted into 4-methoxybenzaldehyde via hydroxylation and subsequent methylation of the 4-C position. The resulting 4-methoxybenzaldehyde was then hydroxylated in the 3-C position followed by methylation into 3,4-dimethoxybenzaldehyde. Based on these findings, a novel metabolic scheme for the biosynthesis of benzylic derivatives in I. resinosum was proposed. The knowledge of the biosynthetic pathway was utilized to produce 4-hydroxy-3-methoxybenzaldehyde (vanillin) from 4-hydroxy-3-methoxybenzoic acid (vanillic acid). This is the first report to elucidate the biosynthetic pathway of benzyl derivatives and production of vanillin from I. resinosum.

Characterization of Key Odorants in Meehan's Mint, Meehania cordata.

Thirty-five odorants from Meehan's mint, Meehania cordata, were identified using solvent-assisted flavor evaporation (SAFE) and aroma extract dilution analysis (AEDA). Twelve compounds with flavor dilution factors ≥16 were quantitated using stable isotope dilution assays (SIDA). Odor activity values (OAVs) and sensory experiments revealed (-)-(E)-pinocarvyl acetate as a key impact odorant contributing to the plant's unique woody and minty odor. Odor simulation experiments revealed a mixture of 10 compounds, including (2E,6Z)-nona-2,6-dienal (OAV 48000), ß-ionone (OAV 33000), (E)-pinocarvyl acetate (OAV 8600), 1-octen-3-one (OAV 2800), and linalool (OAV 990), successfully mimicked the plant odor when combined in their natural concentrations. Three stereoisomers of pinocarvyl acetate were identified including (-)-(E)-, (+)-(E)-, and (-)-(Z)-isomers. The (E) to (Z)-ratio was determined as 95.5% (E) and 0.5% (Z). The enantiomeric ratio of (-)-(E)- to (+)-(E)- was determined as 96% (-)-(E)- and 4% (+)-(E)-pinocarvyl acetate. This study established the basis for future investigations aimed at determining the odorant variability of individual genotypes from natural populations of M. cordata and other members of the Meehenia genus.

Key Odorants from the Fermentation Broth of the Edible Mushroom Ischnoderma resinosum.

Eighteen odorants were identified by applying aroma extract dilution analysis in the liquid fermentation broth of the edible mushroom Ischnoderma resinosum (P. Karst). Eight compounds with flavor dilution factors ≥16 were quantitated in a 16-day sample using stable isotope dilution assays. Odor activity values (OAV) revealed anise-smelling 4-methoxybenzaldehyde (OAV; 1639), vanilla-smelling 3,4-dimethoxybenzaldehyde (OAV; 51), and cherry-smelling benzaldehyde (OAV; 14) as key contributors to the pleasant "candy-like" odor of the fermentation broth. Odor simulation experiments revealed a mixture of five compounds in their natural concentrations mimicked the odor of a 16-day-old fermentation broth. A 30-day time course study was conducted to monitor the production of three odorants in the fungal fermentation broth, where it was revealed that both 3,4-dimethoxybenzaldehyde (10.7 ± 1.0 mg/kg) and benzaldehyde (4.5 ± 0.1 mg/kg) peaked on day 16, whereas 4-methoxybenzaldehyde peaked on day 24 (104.9 ± 4.9 mg/kg).