Significant contribution of amino acids to antioxidant capacity of Japanese rice wine (sake)

BACKGROUND

Various antioxidant components have been reported in Japanese rice wine (sake), while the contribution ratio of each component to the antioxidant capacity of whole sake has not been well understood. In this study, we evaluated the radical absorption capacity (H-ORAC and/or DPPH radical scavenging ability) and antioxidant components of commercially available sake, and estimated the major components contributing to antioxidant capacity.

RESULTS

Water-soluble components with a molecular weight of less than 3000 contributed more than 90% to H-ORAC of sake by measuring the ultrafiltered fraction. The Maillard reaction seemed to have little influence on H-ORAC by browning experiments. The radical absorption capacity of sake showed a strong positive correlation with the amounts of four antioxidant amino acids (Cys, Met, Tyr, Trp) and two phenolic acids (ferulic acid and p-coumaric acid). Evaluating H-ORAC of a sake model solution composed of these antioxidants revealed that the four amino acids showed a clearly higher contribution (25.7-58.2%) than the phenolic acids. In addition, there was a slight synergistic effect when the four amino acids were mixed, whereas such effects were not seen when mixed with the phenolic acids and other sake major components (organic acids, glucose and ethanol).

CONCLUSION

We concluded that the contribution of free amino acids to the radical absorption capacity is quite important in sake. These findings will provide a new perspective for antioxidant researches of sake and many fermented foods. © 2024 Society of Chemical Industry.

Aspergillus oryzae FaeA is responsible for the release of ferulic acid, a precursor of off-odor 4-vinylguaiacol in sake brewing

4-Vinylguaiacol (4-VG) is one of the most common off-flavors found in sake. 4-VG is produced from its precursor, ferulic acid, which is a component of the cell wall of the rice endosperm. The release of ferulic acid in sake brewing is thought to be mediated by feruloyl esterase produced by either Aspergillus oryzae or Saccharomyces cerevisiae. To investigate the effect of FaeA, a feruloyl esterase produced by A. oryzae, its loss-of-function strain was produced by genome co-editing. The feruloyl esterase activity of the faeA-deficient strain was drastically reduced. Sake was fermented using koji with S. cerevisiae strain G046, which can convert ferulic acid to 4-VG. Fermented sake was analyzed by measuring the 4-VG content and sensory evaluation. 4-VG content was reduced to approximately 10% of that of sake fermented with control koji. Sensory evaluation revealed that 4-VG was almost undetectable. Our findings showed that disruption of faeA in A. oryzae is a promising strategy to reduce 4-VG off-flavors in sake.

Medical Application of Substances Derived from Non-Pathogenic Fungi Aspergillus oryzae and A. luchuensis-Containing Koji

Although most fungi cause pathogenicity toward human beings, dynasties of the East Asian region have domesticated and utilized specific fungi for medical applications. The Japanese dynasty and nation have domesticated and utilized koji fermented with non-pathogenic fungus Aspergillus oryzae for more than 1300 years. Recent research has elucidated that koji contains medicinal substances such as Taka-diastase, acid protease, koji glycosylceramide, kojic acid, oligosaccharides, ethyl-α-d-glucoside, ferulic acid, ergothioneine, pyroglutamyl leucine, pyranonigrin A, resistant proteins, deferriferrichrysin, polyamines, Bifidobacterium-stimulating peptides, angiotensin I-converting enzyme inhibitor peptides, 14-dehydroergosterol, beta-glucan, biotin, and citric acid. This review introduces potential medical applications of such medicinal substances to hyperlipidemia, diabetes, hypertension, cardiovascular and cognitive diseases, chronic inflammation, epidermal permeability barrier disruption, coronavirus disease 2019 (COVID-19), and anti-cancer therapy.

1H NMR and LC-MS-based metabolomic approach for evaluation of the seasonality and viticultural practices in wines from São Francisco River Valley, a Brazilian semi-arid region

São Francisco River Valley (SFRV) is a wine-producing semi-arid region in Brazil. Therefore, we used a ¹H NMR and UPLC-MS-based metabolomic approach coupled to chemometrics to evaluate the variability in Chenin Blanc and Syrah wines for two harvest seasons, two vine training system and six rootstocks. Overall, the secondary metabolites were influenced by the three factors studied, whereas the primary metabolites were only by the seasonality. Chenin Blanc wines made in December presented higher content of an unidentified carbohydrate. In Syrah wines, glycerol, tartaric acid, succinic acid and 2,3-butanediol were greater in December, while proline and lactic acid were more abundant in July. For training system, caffeic acid derivatives were increased in wines produced from espalier. Lyre system increased phenolic compounds, organic acids and apocarotenoids. The effect of the rootstocks was less pronounced, affecting basically caffeic acid derivatives. Thus, we expect that our results may assist the winemakers to improve the SFRV wine quality.

Characterization of a cold-active and salt tolerant esterase identified by functional screening of Arctic metagenomic libraries

BACKGROUND

The use of metagenomics in enzyme discovery constitutes a powerful approach to access to genomes of unculturable community of microorganisms and isolate novel valuable biocatalysts for use in a wide range of biotechnological and pharmaceutical fields.

RESULTS

Here we present a novel esterase gene (lip3) identified by functional screening of three fosmid metagenomic libraries, constructed from three marine sediment samples. The sequenced positive fosmid revealed an enzyme of 281 amino acids with similarity to class 3 lipases. The 3D modeling of Lip3 was generated by homology modeling on the basis of four lipases templates [PDB ID: 3O0D, 3NGM, 3G7N, 2QUB] to unravel structural features of this novel enzyme. The catalytic triad of Lip3 was predicted to be Asp207, His267 and the catalytic nucleophile Ser150 in a conserved pentapeptide (GXSXG). The 3D model highlighted the presence of a one-helix lid able to regulate the access of the substrate to the active site when the enzyme binds a hydrophobic interface. Moreover an analysis of the external surface of Lip3 model showed that the majority of the surface regions were hydrophobic (59.6 %) compared with homologous lipases (around 35 %) used as templates. The recombinant Lip3 esterase, expressed and purified from Escherichia coli, preferentially hydrolyzed short and medium length p-nitrophenyl esters with the best substrate being p-nitrophenyl acetate. Further characterization revealed a temperature optimum of 35 °C and a pH optimum of 8.0. Lip3 exhibits a broad temperature stability range and tolerates the presence of DTT, EDTA, PMSF, β-mercaptoethanol and high concentrations of salt. The enzyme was also highly activated by NaCl.

CONCLUSIONS

The biochemical characterization and homology model reveals a novel esterase originating from the marine Arctic metagenomics libraries with features of a cold-active, relatively thermostable and highly halotolerant enzyme. Taken together, these results suggest that this esterase could be a highly valuable candidate for biotechnological applications such as organic synthesis reactions and cheese ripening processes.

Diversity of fungal feruloyl esterases: updated phylogenetic classification, properties, and industrial applications

Feruloyl esterases (FAEs) represent a diverse group of carboxyl esterases that specifically catalyze the hydrolysis of ester bonds between ferulic (hydroxycinnamic) acid and plant cell wall polysaccharides. Therefore, FAEs act as accessory enzymes to assist xylanolytic and pectinolytic enzymes in gaining access to their site of action during biomass conversion. Their ability to release ferulic acid and other hydroxycinnamic acids from plant biomass makes FAEs potential biocatalysts in a wide variety of applications such as in biofuel, food and feed, pulp and paper, cosmetics, and pharmaceutical industries. This review provides an updated overview of the knowledge on fungal FAEs, in particular describing their role in plant biomass degradation, diversity of their biochemical properties and substrate specificities, their regulation and conditions needed for their induction. Furthermore, the discovery of new FAEs using genome mining and phylogenetic analysis of current publicly accessible fungal genomes will also be presented. This has led to a new subfamily classification of fungal FAEs that takes into account both phylogeny and substrate specificity.

Formation of ethyl ferulate from feruloylated oligosaccharide by transesterification of rice koji enzyme under sake mash conditions

Formation of ethyl ferulate (EF) and ferulic acid (FA) under sake mash conditions was studied using feruloylated oligosaccharide (FO), prepared from rice grains, as the substrate for rice koji enzyme. EF and FA were produced from FO over six times faster than from alkyl ferulates however, under the same ethanol concentration, only small differences were observed between the EF/FA ratios when either FO or methyl ferulate were used as substrates. Esterification and hydrolysis of FO or methyl ferulate showed similar pH dependencies and similar EF/FA ratios for each substrate in all of the pH ranges tested. Ethanol concentration clearly affected the EF/FA ratio; the ratio increased as ethanol concentration increased. Formation of EF and FA in the sake mash simulated rice digest was accelerated by addition of exogenous FO. These results indicated that supply of FO to sake mash is a crucial step for EF and FA formation, and ethanol is an influencing factor in the EF/FA ratio. The rice koji enzyme reaction suggested that EF and FA are formed through a common feruloylated enzyme intermediate complex by transesterification or hydrolysis, and these reactions occur competitively.

Molecular conformational analysis, vibrational spectra, NBO analysis and first hyperpolarizability of (2E)-3-phenylprop-2-enoic anhydride based on density functional theory calculations

The conformational behavior and structural stability of (2E)-3-phenylprop-2-enoic anhydride were investigated by using density functional theory. Seventeen possible stable conformations of the title compound were determined and verified with their calculated vibrational frequencies being all positive. The optimized molecular structure, vibrational wavenumbers, corresponding vibrational assignments of (2E)-3-phenylprop-2-enoic anhydride have been investigated experimentally and theoretically using Gaussian09 software package. Potential energy distribution of normal modes vibrations was done using GAR2PED program. The HOMO and LUMO analysis are used to determine the charge transfer within the molecule. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. The calculated first hyperpolarizability of the title compound is 12×10(-30) esu and is 92.31 times that of the standard NLO material urea and the title compound is an attractive object for future studies of nonlinear optical properties. MEP was performed by the DFT method and the predicted infrared intensities and Raman activities have also been reported.