Bioturbation analysis of microbial communities and flavor metabolism in a high-yielding cellulase Bacillus subtilis biofortified Daqu.

In this study, a fortified Daqu (FF Daqu) was prepared using high cellulase-producing Bacillus subtilis, and the effects of in situ fortification on the physicochemical properties, flavor, active microbial community and metabolism of Daqu were analyzed. The saccharification power, liquefaction power, and cellulase activity of the FF Daqu were significantly increased compared with that of the traditional Daqu (CT Daqu). The overall differences in flavor components and their contents were not significant, but the higher alcohols were lower in FF Daqu. The relative abundance of dominant active species in FF Daqu was 85.08% of the total active microbiota higher than 63.42% in CT Daqu, and the biomarkers were Paecilomyces variotii and Aspergillus cristatus, respectively. The enzymes related to starch and sucrose metabolic pathways were up-regulated and expressed in FF Daqu. In the laboratory level simulation of baijiu brewing, the yield of baijiu was increased by 3.36% using FF Daqu.

Combined microbiome and metabolomics analysis of Taorong-type baijiu high-temperature Daqu and medium-temperature Daqu.

Background: Daqu is an essential starter for baijiu brewing in China. However, the microbial enrichment and metabolic characteristics of Daqu formed at different fermentation temperatures are still unclear. Methods: High-throughput sequencing technology and the non-targeted metabolomics were used to compare the microbial communities and metabolites of Taorong-type high-temperature Daqu and middle-temperature Daqu. In this study, the relationship between microorganisms and metabolites was established. Results: The study found that the composition and metabolites of the microbial community differed due to the difference in Daqu-making temperature. The bacterial diversity of Taorong-type high-temperature Daqu was higher than that of middle-temperature Daqu, while the fungal community diversity of Taorong-type middle-temperature Daqu was higher than that of high temperature Daqu. A total of 1,034 differential metabolites were screened from the two types of Daqu, and 76 metabolites with significant differences were detected (P < 0.001 and variable importance in projection (VIP) > 1.15). Tetraacetylethylenediamine is the metabolite with the largest differential fold among the 76 differential metabolites, which can be used as a potential marker metabolite of high-temperature Daqu. Conclusion: This study helps elucidate the microbial assembly mechanisms and functional expression under different processing conditions through a further understanding of the composition and metabolic profile differences of different types of Daqu microflora in Taorong-type baijiu.

Screening and identification of high yield tetramethylpyrazine strains in Nongxiangxing liquor Daqu and study on the mechanism of tetramethylpyrazine production.

BACKGROUND: There are few reports on the breeding of high-yielding tetramethylpyrazine (TTMP) strains in strong-flavor Daqu. In addition, studies on the mechanism of TTMP production in strains are mostly based on common physiological and biochemical indicators, and there is no report on RNA level. Therefore, in this study, a strain with high production of TTMP was screened out from strong-flavor liquor, and transcriptome sequencing analysis was performed to analyze its key metabolic pathways and key genes, and to infer the mechanism of TTMP production in the strain. RESULTS: In this study, a strain with a high yield of tetramethylpyrazine (TTMP) was screened out, and the yield was 29.83 µg mL-1 . The identified strain was Bacillus velezensis, which could increase the content of TTMP in liquor by about 88%. After transcriptome sequencing, a total of 1851 differentially expressed genes were screened, including 1055 up-regulated genes and 796 down-regulated genes. Three pathways related to the production of TTMP were identified by gene ontology (GO) annotation and COG annotation, including carbohydrate metabolism, cell movement and amino acid metabolism. The key genes of TTMP were analyzed, and the factors that might regulate the production of TTMP, such as the transfer of uracil phosphate ribose and glycosyltransferase, were obtained. CONCLUSIONS: A strain of B. velezensis with high TTMP production was screened and identified in strong-flavor Daqu for the first time. The yield of TTMP was 29.83 µg mL-1 , which increased the TTMP content in liquor by 88%. The key metabolic pathways of TTMP production in the strain were obtained: carbohydrate metabolism, cell movement and amino acid metabolism, and the key regulatory genes of each pathway were found, which complemented the gap in gene level in the production regulation of the strain, and provided a theoretical basis for the subsequent study of TTMP in liquor. © 2023 Society of Chemical Industry.

Functional microorganisms in Baijiu Daqu: Research progress and fortification strategy for application.

Daqu is a saccharifying and fermenting starter in the production of Chinese Baijiu; its quality directly affects the quality of Baijiu. The production of Daqu is highly environment-dependent, and after long-term natural domestication, it is rich in a wide variety of microorganisms with a stable composition, which provide complex and diverse enzymes and flavor (precursor) substances and microbiota for Jiupei (Fermented grains) fermentation. However, inoculation with a relatively stable microbial community can lead to a certain upper limit or deficiencies of the physicochemical properties (e.g., saccharification capacity, esterification capacity) of the Daqu and affect the functional expression and aroma formation of the Daqu. Targeted improvement of this problem can be proposed by selecting functional microorganisms to fortify the production of Daqu. This review introduced the isolation, screening, identification and functional characteristics of culture-dependent functional microorganisms in Baijiu-brewing, the core functional microbiota community of Daqu, and the related research progress of functional microorganisms fortified Daqu, and summarized the fortifying strategies of functional microorganisms, aiming to further deepen the application of functional microorganisms fortification in Daqu fermentation and provide ideas for the flavor regulation and quality control of Baijiu.

Optimization of fermentation technology for composite fruit and vegetable wine by response surface methodology and analysis of its aroma components.

Fruit wine has certain health care functions, but fruit wine made from a single fruit or vegetable does not have a good enough color, flavor or nutrient composition. Therefore, this study used fresh carrot (Daucus carota subsp. sativus) and pomegranate (Punica granatum) as raw materials to explore the brewing process of carrot and pomegranate compound wine. The fermentation technology of the composite carrot and pomegranate wine was optimized by a single-factor experiment and Box-Behnken design (BBD), which provided a theoretical foundation for the fermentation of this wine. As per the results, the alcohol content of this composite carrot and pomegranate wine was 12.35% vol. under the optimum fermentation conditions of 28 °C initial temperature, 24% initial sugar content, and with the addition of 64 mg L-1 sulfur dioxide (SO2). In the fermented fruit and vegetable wine, a total of 30 aroma components were detected; 21 composites (such as bornyl acetate, caryophyllene and 3-(2-nitrophenylmethyl)-2-thiazolidinone) were newly generated. The relative content of alcohol flavor composites (such as propionic acid 2-methyl-3-hydroxy-2,2,4-trimethylpentan-1-ol, 2-methyl-2-ethyl-3-hydroxycyclohexyl propanoate and terpinene-4-ol) showed an upward trend, and the relative content of alkene components increased significantly after fermentation. The findings of this study provide an experimental foundation for optimizing fermentation technology and for improving the product quality of composite carrot and pomegranate wine.

Taorong-type Baijiu starter: Analysis of fungal community and metabolic characteristics of middle-temperature Daqu and high-temperature Daqu.

To study the difference between the fungal community compositional and fragrance components in medium- and high-Temperature Taorong-type Baijiu Daqu. The microbial communities and fragrance components of Taorong-type Baijiu Daqu were analyzed using high-throughput sequencing (HTS) and headspace-solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). With an abundance at the phylum and genus levels ≥0.01% as the threshold, 3 phyla, Mucoromycota, Ascomycota, and Basidiomycota, were found in both medium- and high-temperature Daqu, but their abundances differed. At the genus level, 15 and 13 genera were recognized. Rhizopus (72.40%) and Thermomyces (53.32%) accounted for the most significant proportions in medium-temperature and high-temperature Daqu, respectively. Medium-temperature Daqu and high-temperature Daqu were found to have 40 and 29 fragrance components, respectively and contained the highest proportions of pyrazines (53.12%) and acids (32.68%). Correlation analyses between microbes and fragrance components showed that Aspergillus, Hyphopichia, Trichosporon, Alternaria were all highly and positively correlated with pyrazines, but the dominant fungal communities were highly correlated with only a few individual acid compounds but not with acid compounds overall. The unique Daqu -making process and environment lead to these differences.

Methyl jasmonate alleviates chilling injury and keeps intact pericarp structure of pomegranate during low temperature storage.

Pomegranate is a kind of fruit with low temperature sensitivity. Abnormal low temperature can easily lead to chilling injury, which negatively impacts the appearance of fruit, accelerates browning and deterioration, as well as seriously reduces the consumption quality and commodity value of pomegranate. This study was carried out to determine the effect of methyl jasmonate on chilling injury of pomegranate during low temperature storage. The result showed that methyl jasmonate treatment effectively maintained edible quality of pomegranate, suppressed the polyphenol oxidase activity and the development of chilling injury index, and inhibited the decline of total phenol content and the increase of malondialdehyde content and cell membrane permeability. In addition, methyl jasmonate could also enhance the disease resistance of fruit by increasing the content of soluble protein, and effectively maintain the integrity of epidermal cell structure and tissue structure. Overall, the conclusion of this paper is that methyl jasmonate can be used as an effective means to suppress chilling injury in postharvest storage of pomegranate.