Analyses of microbial consortia in the starter of Fen Liquor

Microbial Community Affects Daqu Quality and the Production of Ethanol and Flavor Compounds in Baijiu Fermentation

Daqu is a traditional starter for Baijiu fermentation and is produced by spontaneous fermentation of ground and moistened barley or wheat. The quality of Daqu is traditionally evaluated based on physicochemical and subjective sensory parameters without microbiological analysis. Here, we compared the physicochemical characteristics of qualified (QD) and inferior (ID) Daqu, their microbial communities based on plate counting and PacBio SMRT sequencing of rRNA gene libraries, and their impacts on Baijiu fermentation. The results showed that the glucoamylase and α-amylase activities of QD were significantly higher than those of ID. The counts of yeasts and relative abundances of functional microbes, especially the amylolytic bacterium Bacillus licheniformis and fungi Saccharomycopsis fibuligera and Lichtheimia ramosa, were significantly higher in QD than in ID. The laboratory-scale Baijiu fermentation tests showed that the relative abundances of the amylolytic microbes were higher in the QD than the ID fermentation set, resulting in more efficient fermentation, as indicated by more weight loss and higher moisture content in the former. Consequently, more glycerol, acetic acid, ethanol, and other volatile compounds were produced in the QD than in the ID fermentation set. The results suggest that Daqu quality is determined by, and can be evaluated based on, its microbial community.

Systematic Review of Actinomycetes in the Baijiu Fermentation Microbiome

Actinomycetes (a group of filamentous bacteria) are the dominant microbial order in the Daqu (DQ) fermentation starter and in the pit mud (PM) of the Baijiu fermentation microbiome. Actinomycetes produce many of the key enzymes and flavor components, and supply important precursors, which have a major influence on its characteristic aroma components, to other microorganisms during fermentation. This paper reviews the current progress on actinomycete research related to Baijiu fermentation, including the isolation and identification, distribution, interspecies interactions, systems biology, and main metabolites. The main metabolites and applications of the actinomycetes during Baijiu fermentation are also discussed.

Amylolytic Fungi in the Ethnic Beer Starter “emao” and Their Beer-Producing Attributes

Naturally occurring autochthonous microbes associated with ethnic beer starters are diverse and important as they play different functional roles in beer fermentations. The study on culturable microbes from the ethnic rice beer starter “emao” of the Bodo community of Assam is limited. Here we isolated and identified the culturable fungal diversity associated with emao and screened them for beer-producing capability from glucose and starch substrates. Based on morphology and molecular characterization, the species identified were Candida glabrata (Cgla_RF2), Cyberlindnera fabianii (Cfab_RF37), Hyphopichia burtonii (Hbur_RF19), Mucor circinelloides (Mcir_RF48), Mucor indicus (Mind_RF25), Penicillium citrinum (Pcit_RF32), Rhodosporidiobolus ruineniae (Rrui_RF4 & Rrui_RF43), Saccharomyces cerevisiae (Scer_RF6), Saccharomycopsis fibuligera (Sfib_RF11), and Wickerhamomyces anomalus (Wano_RF3) among which the relative abundance (RA) of W. anomalus was the highest (24%) followed by C. glabrata and H. burtonii (16% in each). Five (Hbur_RF19, Sfib_RF11, Mind_RF25, Mcir_RF48, and Pcit_RF32) of eleven isolates showed amylase positive in the starch medium. Scer_RF6 showed the highest ethanol tolerance (14% v/v) followed by Hbur_RF19 (12% v/v), Cgla_RF2 (11% v/v) and Wano_RF3 (11% v/v). The amylase-positive strains produced beer-containing ethanol in the range of 3.17–7.3 (% v/v) from rice substrate. Although the rice beer produced by amylase-positive strains showed negligible pH difference, other parameters like ethanol, ascorbic acid, total phenol, and antioxidant properties were varied from beer to beer. Antibacterial activities shown by Mcir_RF48 and Pcit_RF32 against the test bacteria were higher with a 23–35 mm zone of inhibition than the other isolates. The present findings reveal the presence of fungi with antibacterial, amylolytic, ethanol fermenting, and antioxidant producing capacity in emao which could the source for future bioprospection.

The Fungal Communities and Flavor Profiles in Different Types of High-Temperature Daqu as Revealed by High-Throughput Sequencing and Electronic Senses

Polymicrobial co-fermentation is among the distinct character of high-temperature Daqu. However, fungal communities in the three types of high-temperature Daqu, namely, white high-temperature Daqu, black high-temperature Daqu, and yellow high-temperature Daqu, are yet to be characterized. In this study, the fungal diversity, taste, and aroma profiles in the three types of high-temperature Daqu were investigated by Illumina MiSeq high-throughput sequencing, electronic tongue, and electronic nose, respectively. Ascomycota and Basidiomycota were detected as the absolute dominant fungal phylum in all types of high-temperature Daqu samples, whereas Thermomyces, Thermoascus, Aspergillus, Rasamsonia, Byssochlamys, and Trichomonascus were identified as the dominant fungal genera. The fungal communities of the three types of high-temperature Daqu differed significantly (p < 0.05), and Thermomyces, Thermoascus, and Monascus could serve as the biomarkers in white high-temperature Daqu, black high-temperature Daqu, and yellow high-temperature Daqu, respectively. The three types of high-temperature Daqu had an extremely significant difference (p < 0.01) in flavor: white high-temperature Daqu was characterized by sourness, bitterness, astringency, richness, methane, alcohols, ketones, nitrogen oxides, and sulfur organic compounds; black high-temperature Daqu was characterized by aftertaste-A, aftertaste-B, methane-aliph, hydrogen, and aromatic compounds; and yellow high-temperature Daqu was characterized by saltiness, umami, methane, alcohols, ketones, nitrogen oxides, and sulfur organic compounds. The fungal communities in the three types of high-temperature Daqu were significantly correlated with taste but not with aroma, and the aroma of high-temperature Daqu was mainly influenced by the dominant fungal genera including Trichomonascus, Aspergillus, Thermoascus, and Thermomyces. The result of the present study enriched and refined our knowledge of high-temperature Daqu, which had positive implications for the development of traditional brewing technique.

Community structure and metabolic potentials of the traditional rice beer starter 'emao'

The emao, a traditional beer starter used in the North-East regions of India produces a high quality of beer from rice substrates; however, its microbial community structure and functional metabolic modules remain unknown. To address this gap, we have used shot-gun whole-metagenome sequencing technology; accordingly, we have detected several enzymes that are known to catalyze saccharification, lignocellulose degradation, and biofuel production indicating the presence of metabolic functionome in the emao. The abundance of eukaryotic microorganisms, specifically the members of Mucoromycota and Ascomycota, dominated over the prokaryotes in the emao compared to previous metagenomic studies on such traditional starters where the relative abundance of prokaryotes occurred higher than the eukaryotes. The family Rhizopodaceae (64.5%) and its genus Rhizopus (64%) were the most dominant ones, followed by Phaffomycetaceae (11.14%) and its genus Wickerhamomyces (10.03%). The family Leuconostocaceae (6.09%) represented by two genera (Leuconostoc and Weissella) was dominant over the other bacteria, and it was the third-highest in overall relative abundance in the emao. The comprehensive microbial species diversity, community structure, and metabolic modules found in the emao are of practical value in the formulation of mixed-microbial cultures for biofuel production from plant-based feedstocks.

Analysis of Difference in Microbial Community and Physicochemical Indices Between Surface and Central Parts of Chinese Special-Flavor Baijiu Daqu

Special-flavor Baijiu is a unique Baijiu in Jiangxi Province, China, whose uniqueness mainly depends on the unique production process of special-flavor Baijiu Daqu. However, the microbial structure and physicochemical indices of different parts of the special-flavor Baijiu Daqu are still unknown. This greatly reduces the actual value of Daqu in the production of special-flavor Baijiu. Therefore, culture-dependent and Illumina MiSeq sequencing methods were used to analyze the microbial structure of special-flavor Baijiu Daqu. The results indicated that there was a complicated microbial diversity in Chinese special-flavor Baijiu Daqu. The predominant bacterial communities were Bacillales, Lactobacillales, and Rhodospirillales, while Saccharomycetales and Eurotiales were the predominant fungal communities. Significant differences in microbial community and distribution were shown between the surface and central parts of Daqu. Acetobacter and Pichia genera were the predominant microorganisms in the surface part of Daqu, whereas Aspergillus, Kroppenstedtia, Oceanobacillus, and Bacillus genera were the predominant microorganisms in the central part of Daqu. Meantime, the different microbial distributions between the surface and central parts of Daqu caused the significant differences in the physicochemical indices. These results can provide an important theoretical basis for improving the brewing process and the quality of special-flavor Baijiu.

Microbiota stratification and succession of amylase-producing Bacillus in traditional Chinese Jiuqu (fermentation starters)

BACKGROUND

Jiuqu are vital saccharifying and fermenting agents for Chinese fermented foods. Natural ventilation during Jiuqu fermentation causes changes in temperature, oxygen and moisture content, resulting in mass and heat gradients from the outer to inner areas of Jiuqu blocks. In the present study, microbiota stratification in Jiuqu was investigated by single molecule real-time sequencing and culture isolation. The contributors of Bacillus to amylase activity of Jiuqu and the dynamics of their biomass during Jiuqu fermentation were also analyzed.

RESULTS

The dominant orders, genera and species between the inner and outer layers of Huangjiu qu (HJQ) were similar, although they displayed greater variance in two layers of Baijiu qu (BJQ). Bacillus possessed the highest diversity (including 27 species) in Jiuqu. Bacillus licheniformis, Bacillus altitudinis, Bacillus subtilis, Bacillus amyloliquefaciens and Bacillus megaterium were most prevalent in HJQ, whereas B. licheniformis, B. amyloliquefaciens and Bacillus cereus were dominant in BJQ. Isolates of B. amyloliquefaciens, B. subtilis and B. cereus exhibited high activities of amylase and glucoamylase. Quantification of Bacillus members possessing genes of α-amylase revealed that B. cereus and B. licheniformis were the most dominant microbes to secret α-amylase in Jiuqu and their biomass were increasing during Jiuqu fermentation.

CONCLUSION

The present study demonstrates the microbial distribution in different layers of Jiuqu and clarifies the Bacillus species processing the activity of α-amylase. These results will help industries control the quality of Jiuqu by rationally selecting starters and optimizing their microbiota. © 2020 Society of Chemical Industry.

Comparison of Bacterial Diversity Between Two Traditional Starters and the Round-Koji-Maker Starter for Traditional Cantonese Chi-Flavor Liquor Brewing

Xiaoqu is a traditional fermentation starter that is used for Chinese liquor production. Although microorganisms in the starters are closely associated with the quality and flavor of liquor, knowledge of the microbiota in xiaoqu is still far from complete, let alone the starters produced by new processes. Here, Illumina MiSeq high-throughput sequencing was applied to study bacterial composition in three types of xiaoqu used in Cantonese soybean-flavor (Chi-flavor) liquor, namely two traditional starters (Jiu Bing and Bing Wan) and a Round-Koji-maker starter (San qu) produced by the automatic starter-making disk machine. The results showed bacterial diversity in traditional starters was similar and higher than that in the Round-Koji-maker starter. Lactobacillus and Pediococcus were the dominant genera in all starters, while other different dominant genera also existed in different starters, which were Weissella, Acetobacter, and Gluconobacter for Jiu Bing, Weissella for Bing Wan, and Bacillus, Acetobacter, Acinetobacter and Klebsiella for San qu, respectively. Meanwhile, Cytophagaceae, one particular microbial family, and some pathogens including Klebsiella, Cronobacter, and Enterobacter were also found in San qu, indicating the automatic starter-making disk machine should be ameliorated before applied into industrial production. These results enriched our knowledge on xiaoqu-related microorganisms and might be helpful in industrial Chi-flavor liquor production and the development of fermentation technology.

New microbial resource: microbial diversity, function and dynamics in Chinese liquor starter

Traditional Chinese liquor (Baijiu) solid state fermentation technology has lasted for several thousand years. The microbial communities that enrich in liquor starter are important for fermentation. However, the microbial communities are still under-characterized. In this study, 454 pyrosequencing technology was applied to comprehensively analyze the microbial diversity, function and dynamics of two most-consumed liquor starters (Jiang- and Nong-flavor) during production. In total, 315 and 83 bacterial genera and 72 and 47 fungal genera were identified in Jiang- and Nong-flavor liquor starter, respectively. The relatively high diversity was observed when the temperature increased to 70 and 62 °C for Jiang- and Nong-flavor liquor starter, respectively. Some thermophilic fungi have already been isolated. Microbial communities that might contribute to ethanol fermentation, saccharification and flavor development were identified and shown to be core communities in correlation-based network analysis. The predictively functional profile of bacterial communities showed significant difference in energy, carbohydrate and amino acid metabolism and the degradation of aromatic compounds between the two kinds of liquor starters. Here we report these liquor starters as a new functionally microbial resource, which can be used for discovering thermophilic and aerobic enzymes and for food and feed preservation.

Metagenomics analysis of microbial communities associated with a traditional rice wine starter culture (Xaj-pitha) of Assam, India

This is the first report on the microbial diversity of xaj-pitha, a rice wine fermentation starter culture through a metagenomics approach involving Illumine-based whole genome shotgun (WGS) sequencing method. Metagenomic DNA was extracted from rice wine starter culture concocted by Ahom community of Assam and analyzed using a MiSeq^® System. A total of 2,78,231 contigs, with an average read length of 640.13 bp, were obtained. Data obtained from the use of several taxonomic profiling tools were compared with previously reported microbial diversity studies through the culture-dependent and culture-independent method. The microbial community revealed the existence of amylase producers, such as Rhizopus delemar, Mucor circinelloides, and Aspergillus sp. Ethanol producers viz., Meyerozyma guilliermondii, Wickerhamomyces ciferrii, Saccharomyces cerevisiae, Candida glabrata, Debaryomyces hansenii, Ogataea parapolymorpha, and Dekkera bruxellensis, were found associated with the starter culture along with a diverse range of opportunistic contaminants. The bacterial microflora was dominated by lactic acid bacteria (LAB). The most frequent occurring LAB was Lactobacillus plantarum, Lactobacillus brevis, Leuconostoc lactis, Weissella cibaria, Lactococcus lactis, Weissella para mesenteroides, Leuconostoc pseudomesenteroides, etc. Our study provided a comprehensive picture of microbial diversity associated with rice wine fermentation starter and indicated the superiority of metagenomic sequencing over previously used techniques.

Microbiota associated with the starter cultures and brewing process of traditional Hong Qu glutinous rice wine

Hong Qu glutinous rice wine (produced mainly in Fujian province, China) is a traditional alcoholic beverage, which is prepared by fermenting cooked rice using a starter containing Monascus purpureus. In this review, the microbial diversity of fermentation starters from Fujian province, including fungi, bacteria, and yeast, is analyzed in comparison with those of "nuruk" (a traditional starter for making alcoholic beverages in Korea). The bacterial organization of Hong Qu starters was vastly variable in species composition and dominated by Bacillus sp. Lactic acid bacteria were also found in some starters. In case of fungi, Monascus sp. was dominant, whereas non-Saccharomyces yeast such as Saccharomycopsis fibuligera was detected. The microorganisms found in the nuruk starter are, in general, not significantly diverse compared with those found in the Hong Qu starter, with the exception of Monascus sp.; however, Hong Qu and nuruk both contain their own unique microbiota, which are quite diverse from each other.

Microbial Community Composition Associated with Maotai Liquor Fermentation

The solid-state fermentation state of Chinese Maotai liquor involves the interaction of several complex microbial communities leading to the generation of the most complex liquor fermentation system in the world and contributes to the unique flavor and aroma of the liquor. In this study, total DNA was extracted from 3 fermented grain samples (FG1, FG2, and FG3) and 12 environmental samples, including Daqu (DA1, DA2, DA3, and DA4), cellar mud (CS1, CS2, and CS3), soil (SL1 and SL2), air (A1 and A2), and sorghum (SH), and the 16S and 18S rRNA genes were amplified. The distribution of typical microorganisms in the samples was analyzed using nested PCR-denaturing gradient gel electrophoresis, while quantitative PCR amplification of 16S rRNA and internal transcribed spacer genes was performed to estimate the microbial abundance present in each sample. The results indicated that Daqu was the primary source of bacteria, followed by the air, soil, and sorghum samples, while the majority of the fungi responsible for Maotai liquor fermentation were from Daqu and sorghum. Highest bacterial concentrations were found in fermented grains, followed by Daqu and sorghum, while the highest fungal concentrations were found in Daqu, followed by sorghum and an air sample from outside the liquor production area. The findings of this study may provide information regarding the mechanisms responsible for flavor development in Maotai liquor, and may be used to further optimize the traditional art of making liquor.

Isolation and characterization of lactic acid bacteria from fresh Chinese traditional rice wines using denaturing gradient gel electrophoresis

Lactic acid bacteria (LAB) are a prevalent bacterial group in rice wine maturation that contributes to flavor, texture, and nutritive value. To better understand LAB diversity in rice wines, 6 rice wine varieties from different regions in China were investigated using denaturing gradient gel electrophoresis (DGGE). Lactobacillus plantarum, L. namurensis, and Pediococcus acidilactici were identified using DGGE. Forty nine isolates were screened using a culture-dependent method. Prominent taxa were identified as Enterococcus sp., Lactobacillus delbrueckii, L. rhamnosus, L. plantarum, and Pediococcus acidilactici. Isolates were grouped and used for fermentation of rice wines. Greater numbers of species involved in fermentation lead to better sensory attributes of wine. DGGE analysis combined with a culture-dependent method can be a tool for investigation of the bacterial compositions of fermented rice wines.

Effect of temperature on microbial composition of starter culture for Chinese light aroma style liquor fermentation

Light aroma style liquor is one of the basic types of Chinese liquor and is produced with a special technique of using a combination of three types of Daqu as starter culture. The succession of incubation temperature, a main operating parameter, and microbial composition in Daqu were investigated during the manufacturing process. The most significant difference in temperature occurred during the middle stage at which the highest and the lowest temperatures were detected in Houhuo (HH) and Qingcha (QC), respectively. It was shown that for the counting data, the population of fungi was identical and that of bacteria was different between three types of Daqu. According to analysis results of microbial community structure using PCR-denaturing gradient gel electrophoresis (PCR-DGGE), lactic acid bacteria were one of the dominant bacterial groups in all of Daqu and fungal diversity in QC was higher than that in HH and Hongxin (HX). The difference in incubation temperature led to the accumulation of different heat-tolerant and heat-sensitive fungi in the completed Daqu. PCA of DGGE profiles revealed that microbial community structure was distinct between three types of Daqu. It was presumed that temperature might play a decisive role in the formation of micro-organism composition in starter cultures.

SIGNIFICANCE AND IMPACT OF THE STUDY

The usage of a combination of three types of Daqu including Qingcha, Hongxin and Houhuo as starter culture is an important characteristic of production technology of Chinese light aroma style liquor. Micro-organisms from the environment naturally inoculated in Daqu are propagated to form the special microbial community under the control of several operating parameters, especially temperature, and finally play various roles in the fermentation process of liquor. An in-depth study of the relationship between incubation temperature and microbiota in Daqu during the manufacturing is fundamental to understand this complicated process and to prepare high-quality starter culture for fermentation.

Characterisation of microbial communities in Chinese liquor fermentation starters Daqu using nested PCR-DGGE

In this study, characterises of the microbial community structures of three typical Chinese liquor Daqu, as well as different kinds of light flavour Daqu were investigated using nested PCR-denaturing gradient gel electrophoresis (DGGE). The results showed that microbial diversity was considerably different, and the microfloral compositions were highly variable among various Daqu. Lactic acid bacteria, which accounted for 30.95 % of all identified bacteria, were dominant in all Daqu samples, whereas Bacillus species were also predominant in the Luzhou (14.8 %) and Langjiu Daqu (18.2 %). Citrobacter and Burkholderia were first identified in light flavour Daqu. Aspergillus was the dominant moulds, and the non-Saccharomyces yeast species, Saccharomycopsis fibuligera, Wallemia sebi, Wallemia muriae, and Pichia subpelliculosa, were the dominant yeasts. Rasamsonia, Galactomyces, Geotrichum and Wallemia were first identified using nested PCR-DGGE. Cluster analysis indicated that the microbial community structures of different Daqu samples exhibited some differences. These may be ascribed to the different peak production temperatures, raw material constituents and microhabitats around the liquor enterprises. The current study provides insights into the microbial community structures of three typical Daqu samples, and may facilitate the development of starter cultures for manufacturing Chinese liquor.

Barcoded pyrosequencing analysis of the bacterial community of Daqu for light-flavour Chinese liquor

The bacterial community of Daqu affects its characteristics and functions by their metabolic products, such as amylase, protease, esterase. In this study, barcoded pyrosequencing was used to analyse the bacterial communities of three kinds of Daqu for light-flavour Chinese liquor brewing. A total of 13672 sequences were identified as bacterial sequences. The Shannon index of QC, HX and GT for clusters sharing 97% homology was 5·0, 4·2 and 4·2, respectively, indicating that QC had the highest biodiversity. The Good's coverage index of QC, HX and GT was 88·2, 93·4 and 93%, respectively, indicating that the vast majority of phylotypes have been detected. Among the three kinds of Daqu, the majority of annotated reads were assigned to two phyla (Firmicutes and Actinobacteria). The phylum Firmicutes was the most abundant group in QC (74·2%), HX (81·4%) and GT (98·6%), and the phylum Actinobacteria was the second in QC (23·9%), HX (17·9%) and GT (1·1%). There were many lactic acid bacteria in all three kinds of Daqu QC (45·8%), HX (46·3%) and GT (24·7%). In addition, the most abundant family in GT was Bacillus, accounting for 65·0%, while in HX, the families Thermoactinomycetaceae and Streptomycetaceae accounted for 19·5 and 14·1%, respectively, and in QC, 13·1% were Streptomycetaceae, 12·2% were heterofermentative Leuconostocaceae.

SIGNIFICANCE AND IMPACT OF THE STUDY

There are three kinds of Daqu (starter material) used for famous Chinese light-flavour liquor brewing, that is Qingcha, Hongxin and Houhuo. Since Daqu was fermented in an open environment, the microbiology communities were different with different kind of Daqu. Objective bacterial communities determined by barcoded pyrosequencing help to speculate possible metabolic productions, even to guess the function of many kind of Daqu in light-flavour liquor brewing.

Natural populations of lactic acid bacteria in douchi from Yunnan Province, China

This research was aimed at isolating and identifying the predominant lactic acid bacteria (LAB) in the traditional Chinese salt-fermented soybean food, douchi, from Yunnan, China. The predominant LAB present were isolated and identified by conventional culture-dependent methods combined with molecular biological methods. Two hundred and sixty isolates were obtained from thirty kinds of traditional fermented douchi from six cities and counties in Yunnan, and those strains were divided into twelve groups by their morphological and biochemical characteristics. Based on 16S ribosomal DNA (rDNA) sequencing and analysis, 56 representative strains were identified as belonging to 6 genera and 14 species: Lactobacillus (4 spp.), Weissella (3 spp.), Pediococcus (2 spp.), Staphylococcus (2 spp.), Enterococcus (1 sp.), and Bacillus (2 spp.). The results show that douchi contains a large natural population of LAB of diverse composition from which some strains could be selected as starters for functional fermented foods. This is the first study on the original douchi from Yunnan, and the results suggest that it may be a useful source for the isolation of LAB. This study has also laid a foundation for further research on developing functional douchi products.

Complex microbiota of a Chinese "Fen" liquor fermentation starter (Fen-Daqu), revealed by culture-dependent and culture-independent methods

Daqu is a traditional fermentation starter that is used for Chinese liquor production. Although partly mechanized, its manufacturing process has remained traditional. We investigated the microbial diversity of Fen-Daqu, a starter for light-flavour liquor, using combined culture-dependent and culture-independent approaches (PCR-DGGE). A total of 190 microbial strains, comprising 109 bacteria and 81 yeasts and moulds, were isolated and identified on the basis of the sequences of their 16S rDNA (bacteria) and 26S rDNA and ITS regions (fungi). DGGE of DNA extracted from Daqu was used to complement the culture-dependent method in order to include non-culturable microbes. Both approaches revealed that Bacillus licheniformis was an abundant bacterial species, and Saccharomycopsis fibuligera, Wickerhamomyces anomalus, and Pichia kudriavzevii were the most common yeasts encountered in Fen-Daqu. Six genera of moulds (Absidia, Aspergillus, Mucor, Rhizopus, Rhizomucor and Penicillium) were found. The potential function of these microorganisms in starters for alcoholic fermentation is discussed. In general the culture-based findings overlapped with those obtained by DGGE by a large extent. However, Weissella cibaria, Weissella confusa, Staphylococcus saprophyticus, Enterobacter aerogenes, Lactobacillus sanfranciscensis, Lactobacillus lactis, and Bacillus megaterium were only revealed by DGGE.

Characterization and comparison of microbial community of different typical Chinese liquor Daqus by PCR-DGGE

AIMS

To identify and compare microbiota in Chinese liquor Daqu, which were produced in the different regions using different production process.

METHODS AND RESULTS

The DNA exacted from Daqu samples was used as a template for PCR with universal primers of 16S rRNA, 26S rRNA and 18S rRNA, respectively. The amplicons were analysed using denaturing gradient gel electrophoresis (DGGE). It was observed that the bacterial DGGE profile indicated high diversity and predominance of lactic acid bacteria. The results showed that Saccharomycopsis fibuligera and Pichia anomal were dominant yeast species and that several non-Saccharomyces yeasts including Hanseniaspora guilliermondii, Debaryomyces hansenii, Issatchenkia orientalis and Trichosporon asahii were also detected. As for fungal DGGE, Aspergillus oryzae and Absidia blakesleeana were the most common species amongst different samples. Based on the DGGE analysis, a few differences in community structure were found between Daqu samples.

CONCLUSIONS

A variety of bacteria, yeast and moulds were identified in Daqu samples, in addition to the present knowledge obtained mainly through the traditional culture-dependent methods. Moreover, production temperature played a more decisive role on the formation of micro-organism composition in Daqu than geographical region.

SIGNIFICANCE AND IMPACT OF THE STUDY

PCR-DGGE technique was used in this study to fully observe and asses all microbial community (including bacteria, yeast and mould) in Chinese liquor Daqu for the first time and proved to be effective in profiling Daqu microbial diversity.