Flavonoids are a large group of plant secondary metabolites with a variety of biological properties and are therefore of interest to many scientists, as they can lead to industrially interesting intermediates. The anaerobic gut bacterium Eubacterium ramulus can catabolize flavonoids, but until now, the pathway has not been experimentally confirmed. In the present work, a chalcone isomerase (CHI) and an enoate reductase (ERED) could be identified through whole genome sequencing and gene motif search. These two enzymes were successfully cloned and expressed in Escherichia coli in their active form, even under aerobic conditions. The catabolic pathway of E. ramulus was confirmed by biotransformations of flavanones into dihydrochalcones. The engineered E. coli strain that expresses both enzymes was used for the conversion of several flavanones, underlining the applicability of this biocatalytic cascade reaction.

Originating from the seedpods of orchids, Vanilla belongs to the most widely appreciated flavours worldwide. Besides the seedpods (beans) also Vanilla extracts and isolated vanillin as the major characteristic aroma compound are commercially used. Different consumer demands and national regulations require appropriate quality control of products arising from the Vanilla plants. Depending on the kind of product and its position in the supply or value chain, different methods for quality control and authentication have to be applied. When examining plant material for instance DNA barcoding can be used, whereas for Vanilla extracts and vanillin analytical quality control is frequently employed. As one of the first chemically synthesized flavouring substances with its first production in the late 19th century vanillin is nowadays manufactured via multiple different chemical and natural routes. To discriminate commercial vanillin qualities by their precursors with respect to the chemical and natural origin stable isotope ratio mass spectrometry (sIRMS) and 1H nuclear resonance spectroscopy (NMR) are the most recognized techniques. This article describes new features to discriminate vanillin from different origins using the δ13C and δ2H ratios of the methoxy group after derivatization with hydriodic acid and subsequent measurement of the released gaseous methyl iodide (CH3I) with sIRMS. The combination of available analytical data by means of multiparametric statistical tools allows for the clear segregation of critical provenience clusters for vanillin, such as (natural) eugenol‐derived qualities from (synthetic) lignin‐ or curcumin‐based products. The approach supports quality and authenticity control for Vanilla‐based products, aiding in meeting customer expectations in this demanding market segment.

As a result of their pleasant odor qualities and low odor thresholds, iso-and anteiso-fatty aldehydes represent promising candidates for applications in flavoring preparations. A novel cyanobacterial α-dioxygenase from Crocosphaera subtropica was heterologously expressed in Escherichia coli and applied for the biotechnological production of C 12 −C 15 branched-chain fatty aldehydes. The enzyme has a sequence identity of less than 40% to well-investigated α-dioxygenase from rice. Contrary to the latter, it efficiently transformed short-chained fatty acids. The kinetic parameters of α-dioxygenase toward unbranched and iso-branchedchain substrates were studied by means of an oxygen-depletion assay. The transformation products (C 12 −C 15 iso-and anteisoaldehydes) were extensively characterized, including their sensory properties. The aldehydes exhibited green-soapy, sweety odors with partial citrus-like, metallic, peppery, and savory-tallowy nuances. Moreover, the two C 14 isomers showed particularly low odor threshold values of 0.2 and 0.3 ng/L in air as determined by means of gas chromatography−olfactometry.

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Lipid extracts of the fungus Flammulina velutipes were found to contain various scarce fatty acids including dodec-11-enoic acid and di- and tri-unsaturated C16 isomers. A biotechnological approach using a heterologously expressed carboxylic acid reductase was developed to transform the fatty acids into the respective aldehydes, yielding inter alia dodec-11-enal. Supplementation studies gave insights into the fungal biosynthesis of this rarely occurring acid and suggested a terminal desaturation of lauric acid being responsible for its formation. A systematic structure–odor relationship assessment of terminally unsaturated aldehydes (C7–C13) revealed odor thresholds in the range of 0.24–22 μg/L in aqueous solution and 0.039–29 ng/L in air. In both cases, non-8-enal was identified as the most potent compound. All aldehydes exhibited green odor qualities. Short-chained substances were additionally associated with grassy, melon-, and cucumber-like notes, while longer-chained homologs smelled soapy and coriander leaf-like with partly herbaceous nuances. Dodec-11-enal turned out to be of highly pleasant scent without off-notes.

Chalcone isomerase (CHI) is a key enzyme in the biosynthesis of flavonoids in plants. The first bacterial CHI (CHI era ) was identified from Eubacterium ramulus, but its distribution, evolutionary source, substrate scope, and stereoselectivity are still unclear. Here, we describe the identification of 66 novel bacterial CHIs from Genbank using a novel Sequence-Structure-Function-Evolution (SSFE) strategy. These novel bacterial CHIs show diversity in substrate specificity towards various hydroxylated and methoxylated chalcones. The mutagenesis of CHI era according to the substrate binding models of these novel bacterial CHIs resulted in several variants with greatly improved activity towards these chalcones. Furthermore, the preparative scale conversion catalyzed by bacterial CHIs has been performed for five chalcones and revealed (S)-selectivity with up to 96 % ee, which provides an alternative biocatalytic route for the synthesis of (S)-flavanones in high yields.Nature produces an enormous variety of biomolecules, among which flavonoids are a large class of secondary metabolites mainly derived from plants. Flavonoids have many functions in plants, such as flower coloration, UV filtration, symbiotic nitrogen fixation, and floral pigmentation. In addition, they also act as chemical messengers, physiological regulators, cell cycle inhibitors, and antibiotics against plant diseases. [1] In our long history of using medicinal[*] B.

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