The complete genome sequence of the thermophilic bacterium Laceyella sacchari FBKL4.010 reveals the basis for tetramethylpyrazine biosynthesis in Moutai-flavor Daqu

Bacillus that produces TTMP enhances the total ester content in Baijiu through biofortification

TTMP is a key flavor compound in Baijiu and also has potential health benefits. Bacillus are vital producers of TTMP; however, the connection between Bacillus in strong-flavor Daqu and TTMP is restricted. In this study, morphological and molecular biological screening and identification of Bacillus strains in strong-flavor Daqu were carried out, and their TTMP production capabilities were evaluated. Additionally, the influence of the selected strains on Baijiu flavor was assessed through simulated fermentation experiments. The experimental results demonstrated that out of the 18 strains of Bacillus spores screened, 12 could produce TTMP, indicating a diverse population of Bacillus spores capable of generating pyrazine compounds in Daqu. Among these, Bacillus subtilis YR-5 yields the highest TTMP at 761.32 mg/L, followed by Bacillus velzensis YR-3 and Bacillus velzensis YR-12 with yields of 553.25 mg/L and 341.19 mg/L, respectively. Under simulated fermentation conditions, the TTMP content increased significantly from 0.19 mg/mL to 0.63 mg/mL, 0.92 mg/mL, and 0.53 mg/mL after adding YR-3, YR-5, and YR-12 respectively; meanwhile, ester content in fermentation system increased by 69.84%,79.35%, and 64.15% respectively. These findings imply that the functional microorganisms required in the search for Baijiu can be screened and identified in Daqu, and the selected strains can be utilized for biofortification to enhance the content of TTMP in Baijiu and improve the flavor of Baijiu.

Screening and genomic evaluation of keratinolytic protease producing Chryseobacterium sp. from tannery waste and its potential application in dehairing of goat skin

Lime and Na2S, used in dehairing in the tannery industry, cause the generation of toxic wastes. Ecological security and financial issues demand a look for innovative approaches to leather dehairing free from pollution. The primary goal of this investigation was to explore keratinolytic protease producing bacteria from tannery waste, their genomic evaluation and to assess their possible use in the dehairing process. A newly isolated Gram-negative bacterium (LRI-TA6) was characterized and checked for its keratinolytic protease producing ability. The strain was identified as Chryseobacterium cucumeris through whole genome sequencing. The genome was 4,541,898 bp in size and contain 4,426 protein coding sequences (CDS) with 36.38 % of GC content. Twenty-five open reading frames (CDS) were found as protease producing genes notably DegQ (serine protease), DegS, and ATP-dependent protease DP (EC 3.4.21.-). The isolate revealed enzyme production throughout an extended pH range of 5.0 to 8.0, and a broad temperature range of 10 °C to 38 °C. The isolate LRI-TA6 was sensitive to all five antibiotics (amoxicillin, tetracycline, gentamicin, ciprofloxacin, and vancomycin) with zone diameter ranges from 17.2 ± 0.8 to 32 ± 0.0 mm. The enzyme was shown to have 29.9 ± 6.7 and 83.6 ± 0.2 U/ml of keratinolytic and proteolytic activity, respectively. By employing crude keratinase, the removal of hair from goat skin was accomplished in 18 h. This study is the first report to isolate and characterize C. cucumeris from tannery waste and also the amazing 18 h dehairing capabilities and thus might be utilized for further studies towards commercial synthesis of keratinase for use in leather processing sectors.

Revealing the Differences in Microbial Community and Quality of High-Temperature Daqu in the Southern Sichuan-Northern Guizhou Region

High-temperature Daqu is crucial to Jiang-flavor Baijiu production in the Southern Sichuan-Northern Guizhou region of China. However, the complex interplay among microorganisms, enzymes, and metabolites in the Daqu from this region requires further investigation. This study compared four high-temperature Daqu samples from this region, analyzing their physicochemical properties, enzyme activities, volatile compounds, and microbial community composition and function, and exploring the influence of microorganisms on the saccharification and aroma-formation function of Daqu in combination with correlation analysis. The microbial communities in the Daqu samples exhibited functional redundancy, with Desmospora sp. 8437 being consistently dominant (3.6-7.3%). Members of the family Bacillaceae were the principal factors contributing to the differences in starch degradation capacity, protein degradation capacity, and pyrazine content among the Daqu samples, mainly through the amylases and proteases they produce. Kroppenstedtia spp. were principal factors causing the differences in aldehyde and ketone contents, primarily via the lipid degradation enzymes they synthesize. Overall, the bacterial community composition of Daqu greatly influenced its characteristics. This study provided a theoretical basis for understanding the diversity of high-temperature Daqu in the Southern Sichuan-Northern Guizhou region.

Progress on the Synthesis Pathways and Pharmacological Effects of Naturally Occurring Pyrazines

As one of the most essential types of heterocyclic compounds, pyrazines have a characteristic smell and taste and have a wide range of commercial applications, especially in the food industry. With the development of the food industry, the demand for pyrazines has increased. Therefore, understanding the properties, functions, and synthetic pathways of pyrazines is one of the fundamental methods to produce, control, and apply pyrazines in food or medical systems. In this review, we provide an overview of the synthesis pathways and physiological or pharmacological functions of naturally occurring pyrazines. In particular, we focus on the biosynthesis and pharmacological effects of 2,3,5,6-Tetramethylpyrazine (TTMP), 2,5-Dimethylpyrazine (2,5-DMP), and 2,3,5-trimethylpyrazine (TMP). Furthermore, areas where further research on pyrazines is needed are discussed in this work.

The mechanism of Laceyella sacchari FBKL4.010 produced tetramethylpyrazine in the liquid fermentation by comparative transcriptomic techniques

Tetramethylpyrazine (TTMP) is considered a crucial flavor component in Moutai-flavored liquor. Laceyeella sacchari FBKL4.010 (L. sacchari) is the dominant species found in Moutai-flavor Daqu, and this study aims to determine the mechanism by which L. sacchari produces TTMP during liquid fermentation of Moutai-flavor Daqu. The results of the liquid fermentation performance demonstrated a gradual increase in biomass over time, while there was a gradual decline in residual glucose content and pH value. Furthermore, analysis of volatile components revealed that liquid fermentation significantly enhanced the production of TTMP in Moutai-flavor Daqu, with the relative content of TTMP reaching 14.24 mg/L after 96 h of liquid fermentation. Additionally, to explore the synthesis mechanism of TTMP, we compared differentially expressed genes (DEGs) of L. sacchari between 24 and 96 h using comparative transcriptomic techniques. The results indicated that DEGs involved in isoleucine, valine, and leucine biosynthesis pathway were upregulated, while those associated with isoleucine, valine, and leucine degradation pathway were downregulated, suggesting that the valine, leucine, and isoleucine biosynthesis pathway primarily contributes ammonia for TTMP synthesis. The findings of this study present an opportunity for further elucidating the production process of TTMP in Moutai-flavor Daqu during liquid fermentation.

Analysis of fermentation control factors on volatile compounds of primary microorganisms in Jiang-flavor Daqu

Chinese Jiang-flavor Baijiu is the most widely consumed liquor. Jiang-flavor Daqu, a fermentation starter, is important sources of key flavors of Jiang-flavor Baijiu. Some microbes play significant roles in flavor formation of Daqu. In order to clarify the microbial population that promotes the formation of Daqu flavor, we use high throughput sequencing technology combined with headspace solid-phase microextraction gas chromatography-mass spectrometry to investigate microbial population and volatile compounds in Jiang-flavor Daqu. In addition, the dynamic changes of physicochemical factors and enzyme activities in Jiang-flavor Daqu were investigated. Correlations between microbial population, volatile compounds, physicochemical factors, and enzyme activities of Jiang-flavor Daqu were disclosed by redundancy analysis and Spearman correlation analysis. A total of 66 volatile compounds were identified and 14 primary microorganisms were selected. Results showed that high temperature environment could promote the formation of acids, aldehydes and ketones, phenols, furans by affecting the growth of Monascus, Trichomonascus, Cutaneotrichosporon, Wallemia, Millerozyma, Nigrospora, Cladosporium, Bacillus, and Pediococcus in the early fermentation stage. While high nitrogen environment was more suitable for the growth of Virgibacillus and Kroppenstedtia, who could promote the formation of pyrazines in the late fermentation stage. PRACTICAL APPLICATIONS: This study has provided a scientific basis for the directed regulation of Daqu fermentation through physicochemical factors, developed scientific basis for artificially constructing Daqu microbial population and obtaining an easy-to-operate, reproducible fermentation system for Daqu production.

Analysis of microbial community, physiochemical indices, and volatile compounds of Chinese te-flavor baijiu daqu produced in different seasons

BACKGROUND

Chinese te-flavor baijiu (CTF), the most famous Chinese baijiu in Jiangxi province, China, is made from a unique daqu. Its characteristic style is closely related to the daqu used for fermentation. However, current studies on the effects of different production seasons on microbial communities, physicochemical indices, and volatile compounds in CTF daqu are very rare.

RESULTS

The relationships of microbial communities, physicochemical indices, and volatile compounds in CTF daqu produced in summer (July and August) and autumn (September and October) were studied. The results of Illumina MiSeq sequencing indicated that there was greater bacterial diversity in the CTF daqu-7 (produced in July) and CTF daqu-8 (produced in August) and greater fungal diversity in the CTF daqu-9 (produced in September) and CTF daqu-10 (produced in October). The physicochemical indices of CTF daqu produced in different seasons were significantly different. It was determined that CTF daqu-9 had the highest esterification and liquefaction abilities. A total of 44 volatile compounds, including alcohols, esters, aldehydes, and ketones were identified in CTF daqu produced during different seasons. Among them, CTF daqu-9 had the greatest alcohol content.

CONCLUSION

September (early autumn) is the best production period for CTF daqu. The results of the study provide a theoretical basis for the standardized and uniform production of Chinese baijiu. © 2021 Society of Chemical Industry.

High-throughput sequencing of the microbial diversity of roasted-sesame-like flavored Daqu with different characteristics

The purpose of this experiment was to analyze the microbial community diversity in three Daqu samples displaying different characteristics in the same Daqu fermentation chamber. A high throughput sequencing technique was used to detect the microbial abundance and diversity in these Daqu samples. Of the three samples, the microbial diversity in the Black sample (sample B) was significantly higher than in the other two. At the genus level, Saccharopolyspora, Bacillus, Lentibacillus, Staphylococcus, Kroppenstedtia, and Thermoactinomyces were the primary bacterial groups in the sesame-flavored liquor, while Thermomyces, Thermoascus, and Aspergillus represented the main fungal groups. In sample B, the dominant bacteria were Thermoactinomyces, Saccharopolyspora, and Pseudomonas. In the White sample (sample W), Thermoactinomyces was the most abundant, followed by Saccharopolyspora and Lentibacillus. Staphylococcus dominated in the Yellow sample (sample Y), followed by Bacillus and Kroppenstedtia. Regarding the fungi in the three samples, Thermomyces accounted for 93.70% in sample B, and Aspergillus dominated in sample W, while the Thermoascus and Aspergillus content were similar in the sample Y. This study examined the microbial diversity in liquor Daqu with different sesame flavors, providing a foundation for microbial regulation, while investigating the relationship between flavored liquor compounds and microorganisms.

Comprehensive evaluation of physicochemical properties and antioxidant activity of B. subtilis-fermented polished adlay subjected to different drying methods

The physicochemical properties and antioxidant activity of B. subtilis-fermented polished adlay (BPA) subjected to different drying methods (hot-air drying, HAD; infrared-radiation drying, IRD; vacuum drying, VD; microwave-vacuum drying, MVD; and freeze-vacuum drying, FVD) were evaluated in this study. Results showed FVD was ideal for maintaining the natural appearance and higher contents of proximate compositions, free fatty acids, tetramethylpyrazine (6.91 mg/g DW), coixol (0.62 mg/g DW), coixenolide (4.21% DW), coixan (35.10% DW), and triterpenoids (17.41 mg/g DW). The higher contents of total phenolics and flavonoids, stronger antioxidant activity, and higher color differences were observed in HAD and IRD samples. MVD displayed the shorter drying time, higher γ-aminobutyric acid content, and higher retention ratios of tetramethylpyrazine (75.54%), coixol (87.10%), coixenolide (98.57%), and coixan (99.11%). Pearson's correlation coefficient exhibited that the positive correlation between the contents of phenolics and flavonoids and the antioxidant activities of all dried BPA samples was observed (R 2 > 0.881, p < .05). Principal component analysis showed that the top three categories of comprehensive quality were FVD-, MVD-, and VD-treated BPA samples. In conclusion, MVD should be a potential preservation method to obtain high-quality dried BPA for short drying time and high comprehensive quality.

The complete genome sequence of the thermophilic bacterium Laceyella sacchari FBKL4.010 reveals the basis for tetramethylpyrazine biosynthesis in Moutai-flavor Daqu

The genus Laceyella consists of a thermophilic filamentous bacteria. The pure isolate of Laceyella sacchari FBKL4.010 was isolated from Moutai‐flavor Daqu, Guizhou Province, China. In this study, the whole genome was sequenced and analyzed. The complete genome consists of one 3,374,379‐bp circular chromosome with 3,145 coding sequences (CDSs), seven clustered regularly interspaced short palindromic repeat (CRISPR) regions of 12 CRISPRs. Moreover, we identified that the genome contains genes encoding key enzymes such as proteases, peptidases, and acetolactate synthase (ALS) of the tetramethylpyrazine metabolic pathway. Metabolic pathways relevant to tetramethylpyrazine synthesis were also reconstructed based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) PATHWAY database. Annotation and syntenic analyses using antiSMASH 4.0 also revealed the presence of two gene clusters in this strain that differ from known tetramethylpyrazine synthesis clusters, with one encoding amino acid dehydrogenase (ADH) and the other encoding transaminase in tetramethylpyrazine metabolism. The results of this study provide flavor and genomic references for further research on the flavor‐producing functions of strain FBKL4.010 in the Moutai liquor‐making process.