BACKGROUND: Due to the complexity of the metabolic pathway network of active ingredients, precise targeted synthesis of any active ingredient on a synthetic network is a huge challenge. Based on a complete analysis of the active ingredient pathway in a species, this goal can be achieved by elucidating the functional differences of each enzyme in the pathway and achieving this goal through different combinations. Lignans are a class of phytoestrogens that are present abundantly in plants and play a role in various physiological activities of plants due to their structural diversity. In addition, lignans offer various medicinal benefits to humans. Despite their value, the low concentration of lignans in plants limits their extraction and utilization. Recently, synthetic biology approaches have been explored for lignan production, but achieving the synthesis of most lignans, especially the more valuable lignan glycosides, across the entire synthetic network remains incomplete.
RESULTS: By evaluating various gene construction methods and sequences, we determined that the pCDF-Duet-Prx02-PsVAO gene construction was the most effective for the production of (+)-pinoresinol, yielding up to 698.9 mg/L after shake-flask fermentation. Based on the stable production of (+)-pinoresinol, we synthesized downstream metabolites in vivo. By comparing different fermentation methods, including \"one-cell, one-pot\" and \"multicellular one-pot\", we determined that the \"multicellular one-pot\" method was more effective for producing (+)-lariciresinol, (-)-secoisolariciresinol, (-)-matairesinol, and their glycoside products. The \"multicellular one-pot\" fermentation yielded 434.08 mg/L of (+)-lariciresinol, 96.81 mg/L of (-)-secoisolariciresinol, and 45.14 mg/L of (-)-matairesinol. Subsequently, ultilizing the strict substrate recognition pecificities of UDP-glycosyltransferase (UGT) incorporating the native uridine diphosphate glucose (UDPG) Module for in vivo synthesis of glycoside products resulted in the following yields: (+)-pinoresinol glucoside: 1.71 mg/L, (+)-lariciresinol-4-O-D-glucopyranoside: 1.3 mg/L, (+)-lariciresinol-4\'-O-D-glucopyranoside: 836 µg/L, (-)-secoisolariciresinol monoglucoside: 103.77 µg/L, (-)-matairesinol-4-O-D-glucopyranoside: 86.79 µg/L, and (-)-matairesinol-4\'-O-D-glucopyranoside: 74.5 µg/L.
CONCLUSIONS: By using various construction and fermentation methods, we successfully synthesized 10 products of the lignan pathway in Isatis indigotica Fort in Escherichia coli, with eugenol as substrate. Additionally, we obtained a diverse range of lignan products by combining different modules, setting a foundation for future high-yield lignan production.

Edible mushrooms, both wild and cultivated, can be seen as healthy functional food. More and more valuable compounds are obtained from mycelia of macromycetes. However, there was limited report about the medicinal fungus Laetiporus versisporus (Lloyd) Imazeki. Herein, L. versisporus was fermented on rice media and the secondary metabolites of mycelia were investigated. In this study, two-step method was used to obtain fermented products, silica gel column chromatography, recrystallization, medium pressure column chromatography, preparative thin-layer chromatography were applied to separate the chemical constituents. Nine chemical compounds (1-9) including one new triterpenoid acid versisponic acid F were identified by NMR (nuclear magnetic resonance) spectroscopy and MS (mass spectrometry). Seven compounds including monolinoleoyl glycerol, linoleic acid, ergosta-5, 7, 22-triene-3β-ol, β-sitosterol, daucosterol, versisponic acid F were isolated for the first time from L. versisporus.

Improving the freezing resistance of yeast in dough starters is one of the most effective methods to promote the healthy development of frozen dough technology. When the dough starter was composed of yeast, lactic acid bacteria and acetic acid bacteria, the microbial proportion was 10:1:5, and the ratio of wheat flour to corn flour was 1:1. The proline contents of the starters and the survival rates and fermentation capacity of yeast significantly increased compared with those of the starter composed of yeast and wheat flour only (P < 0.05). Laser confocal microscopy observation showed that the cell membrane damage of yeast obviously decreased. Low-field nuclear magnetic resonance method revealed that the water distribution state of starters changed. Adding corn flour and acetic acid bacteria to dough starter in appropriate proportions improves yeast freezing resistance.

Rice wine, well known for its unique flavor, rich nutritional value, and health benefits, has potential for extensive market development. Rhizopus and Aspergillus are among several microorganisms used in rice wine brewing and are crucial for determining rice wine quality. The strains were isolated via Rose Bengal and starch as a combined separation medium, followed by oenological property and sensory evaluation screening. The strain exhibiting the best performance can be screened using the traditional rice wine Qu. The strains YM-8, YM-10, and YM-16, which exhibited strong saccharification and fermentation performance along with good flavor and taste, were obtained from traditional rice wine Qu. Based on ITS genetic sequence analysis, the YM-8, YM-10, and YM-16 strains were identified as Rhizopus microsporus, Rhizopus arrhizus, and Aspergillus oryzae. The optimum growth temperature of each of the three strains was 30°C, 32°C, and 30°C, and the optimum initial pH was 6.0, 6.5, and 6.5, respectively. The activities of α-amylase, glucoamylase, and protease of YM-16 were highest at 220.23±1.88, 1,269.04±30.32, and 175.16±1.81 U/g, respectively. The amino acid content of rice wine fermented in a 20-L bioreactor with the three mold strains was higher than that of the control group, except for arginine, which was significantly lower than that of the control group. The total amino acid content and the total content of each type of amino acid were ranked as YM-16 > YM-8 > YM-10 > control group, and the amino acid content varied greatly among the strains. The control group had a higher content, whereas YM-8 and YM-16 had lower contents of volatile aroma components than the control group and had the basic flavor substances needed for rice wine, which is conducive to the formation of rice wine aroma. This selected strain, YM-16, has strong saccharification and fermentation ability, is a rich enzyme system, and improves the flavor of rice wine, thereby demonstrating its suitability as a production strain for brewing.

A fluorescence probe based on molecularly imprinted polymers on red emissive biomass-derived carbon dots (r-BCDs@MIPs) was developed to detect tyramine in fermented meat products. The red emissive biomass-derived carbon dots (r-BCDs) were synthesized by the one-step solvothermal method using discarded passion fruit shells as raw materials. The fluorescence emission peak of r-BCDs was at 670 nm, and the relative quantum yield (QY) was about 2.44%. Molecularly imprinted sensing materials were prepared with r-BCDs as fluorescent centers for the detection of trace tyramine, which showed a good linear response in the concentration range of tyramine from 1 to 40 µg L-1. The linear correlation coefficient was 0.9837, and the limit of detection was 0.77 µg L-1. The method was successfully applied to the determination of tyramine in fermented meat products, and the recovery was 87.17-106.02%. The reliability of the results was verified through high-performance liquid chromatography (HPLC). Furthermore, we combined the r-BCDs@MIPs with smartphone-assisted signal readout to achieve real-time detection of tyramine in real samples. Considering its simplicity and convenience, the method could be used as a rapid and low-cost promising platform with broad application prospects for on-site detection of trace tyramine with smartphone-assisted signal readout.

Consumption of wheat bran is associated with health benefits. However, the insoluble cell layer fiber and considerable levels of anti-nutritional factors limit bioavailability of wheat bran, which can be effectively improved through fermentation. To comprehensively elucidate the precise biotransformation and health benefits mechanisms underlying wheat bran fermentation. This review investigates current fermentation biotechnology for wheat bran, nutritional effects of fermented wheat bran, mechanisms by which fermented wheat bran induces health benefits, and the application of fermented wheat bran in food systems. The potential strategies to improve fermented wheat bran and existing limitations on its application are also covered. Current findings support that microorganisms produce enzymes that degrade the cell wall fiber of wheat bran during the fermentation, releasing nutrients and producing new active substances while degrading anti-nutrient factors in order to effectively improve nutrient bioavailability, enhance antioxidant activity, and regulate gut microbes for health effects. Fermentation has been an effective way to degrade cell wall fiber, thereby improving nutrition and quality of whole grain or bran-rich food products. Currently, there is a lack of standardization in fermentation and human intervention studies. In conclusion, understanding effects of fermentation on wheat bran should guide the development and application of bran-rich products.

There has been growing interest in the use of mixed cultures comprised of Oenococcus oeni and Saccharomyces cerevisiae to produce wine with local style and typicality. This study has investigated the influence of the inoculation protocol of O. oeni on the fermentation kinetics and aromatic profile of Chardonnay wine. The one selected autochthonous O. oeni strain (ZX-1) inoculated at different stages of the alcoholic fermentation process successfully completed malolactic fermentation (MLF). Co-inoculum of S. cerevisiae and O. oeni enabled simultaneous alcoholic fermentation and MLF, leading to at least a 30 % reduction in the total fermentation time when compared to the sequential inoculation process, which was attributed to the lower ethanol stress. Meanwhile, co-inoculum stimulated the accumulation of volatile aroma compounds in Chardonnay wine. In particular, the mixed modality where the O. oeni strain ZX-1 was inoculated 48 h after S. cerevisiae allowed higher levels of terpenes, acetates, short-chain, and medium-chain fatty acid ethyl esters to be produced, which may result in the enhanced floral and fruity attributes of wine. Aroma reconstitution and omission models analysis revealed that the accumulation of linalool, geraniol, isoamyl acetate, ethyl hexanoate, and ethyl caprylate during the mixed fermentation process enhanced the stone fruit, tropical fruit, and citrus aromas in Chardonnay wine. Therefore, the simultaneous fermentation of S. cerevisiae and autochthonous O. oeni ZX-1 has a positive effect on MLF and contributes to producing wines with distinctive style.

To improve the color stability of anthocyanins (ACNs) in blueberry fermented beverage, the intermolecular copigmentation between ACNs and 3 different phenolic compounds, including (-)-epigallocatechin gallate (EGCG), ferulic acid (FA), and gallic acid (GA) as copigments, was compared in the model and the real blueberry fermented beverage, respectively. The copigmented ACNs by EGCG presented a high absorbance (0.34 a.u.) and redness (27.09 ± 0.17) in the model blueberry fermented beverage. The copigmentation by the participation of the 3 different phenolic compounds showed all a spontaneous exothermic reaction, and the Gibbs free energy (ΔG°) of the system was lowest (-5.90 kJ/mol) using EGCG as copigment. Furthermore, the molecular docking model verified that binary complexes formed between ACNs and copigments by hydrogen bonds and π-π stacking. There was a high absorbance (1.02 a.u.), percentage polymeric color (PC%, 68.3 %), and good color saturation (C*ab, 43.28) in the real blueberry fermented beverage aged for 90 days, and more malvidin-3-O-glucoside had been preserved in the wine using EGCG as copigment. This finding may guide future industrial production of blueberry fermented beverage with improved color.

Chinese steamed bread (CSB) is an important staple of the Chinese people, and its flavor profile is mostly affected by wheat varieties among others. This study selected wheat flour made from three different wheat varieties and investigated their contribution to the CSB flavor profile in terms of metabolism. Thirteen aroma-active compounds identified by GC-O were determined as the main contributors to the different aroma profiles of three CSBs. 350 sensory trait-related metabolites were obtained from five key modules via weighted gene co-expression network analysis. It was found that the sensory characteristics of CSBs made of different wheat flour were significantly different. The higher abundance of lipids in Yongliang No.4 (YL04) wheat flour was converted to large number of fatty acids in fermented dough, which led to the bitterness of CSB. Besides, the abundance in organic acids and fatty acids contributed to the sour, milky, wetness and roughness attributes of YL04-CSB. More fatty amides and flavonoids in Jiangsu Red Durum wheat flour contributed to the fermented and winey attributes of CSB. Carbohydrates with higher abundance in Canadian wheat flour was involved in sugar-amine reaction and glucose conversion, which enhanced the sweetness of CSB. In addition, fatty acids, organic acids, amino acids, and glucose were crucial metabolites which can further formed into various characteristic compounds such as hexanal, hexanol, 2,3-butanediol, acetoin, and 2,3-butanedione and thus contributed to the winey, fresh sweet, and green aroma properties. This study is conductive to better understand the evolution of the compounds that affect the quality and aroma of CSBs.

Ethyl hexanoate and ethyl butyrate are indispensable flavor metabolites in strong-flavor Baijiu (SFB), but batch production instability in fermenting grains can reduce the quality of distilled Baijiu. Biofortification of the fermentation process by designing a targeted microbial collaboration pattern is an effective method to stabilize the quality of Baijiu. In this study, we explored the metabolism under co-culture liquid fermentation with Clostridium tyrobutyricum DB041 and Saccharomyces cerevisiae YS219 and investigated the effects of inoculation with two functional microorganisms on physicochemical factors, flavor metabolites, and microbial communities in solid-state simulated fermentation of SFB for the first time. The headspace solid-phase microextraction-gas chromatography-mass spectrometry results showed that ethyl butyrate and ethyl hexanoate significantly increased in fermented grain. High-throughput sequencing analysis showed that Pediococcus, Lactobacillus, Weissella, Clostridium_sensu_stricto_12, and Saccharomyces emerged as the dominant microorganisms at the end of fermentation. Co-occurrence analysis showed that ethyl hexanoate and ethyl butyrate were significantly correlated (|r| > 0.5, P < 0.05) with a cluster of interactions dominated by lactic acid bacteria (Pediococcus, Lactobacillus, Weissella, and Lactococcus), which was driven by the functional C. tyrobutyricum and S. cerevisiae. Mantel test showed that moisture and reducing sugars were the main physicochemical factor affecting microbial collaboration (|r| > 0.7, P < 0.05). Taken together, the collaborative microbial pattern of inoculation with C. tyrobutyricum and S. cerevisiae showed positive results in enhancing typical flavor metabolites and the synergistic effects of microorganisms in SFB.