Microbiota Dynamics Associated with Environmental Conditions and Potential Roles of Cellulolytic Communities in Traditional Chinese Cereal Starter Solid-State Fermentation

Effect of Solid-State Fermentation of Hericium erinaceus on the Structure and Physicochemical Properties of Soluble Dietary Fiber from Corn Husk

Corn husk, a by-product of corn starch production and processing, contains high-quality dietary fiber (DF). Our study compares and analyzes the impact of Hericium erinaceus solid-state fermentation (SSF) on the structure and physicochemical characteristics of soluble dietary fiber (SDF) of corn husks. The study also investigates the kinetics of SSF of H. erinaceus in this process. The scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) results revealed significant structural changes in corn husk SDF before and after fermentation, with a significant elevation in the functional group numbers. The data indicate that the fermented corn husk SDF's water-holding, swelling, and oil-holding capacities increased to 1.57, 1.95, and 1.80 times those of the pre-fermentation SDF, respectively. Additionally, the results suggest that changes in extracellular enzyme activity and nutrient composition during SSF of H. erinaceus are closely associated with the mycelium growth stage, with a mutual promotion or inhibition relationship between the two. Our study offers a foundation for corn husk SDF fermentation and is relevant to the bioconversion of maize processing by-products.

Exploring the controllability of the Baijiu fermentation process with microbiota orientation

Product quality and stability improvement is important for development of the Baijiu industry. Generally, Baijiu brewing is carried out in a spontaneous fermentation system mediated by microbiota. Thus, complexity and instability are major features. Due to the insufficient understanding of the mechanism for producing Baijiu, the precise control of the fermentation progress has still not been realized, ultimately affecting product quality and stability. The flavor of Baijiu is the most important factor in determining its quality and is formed by microbiota under the driving force of various physicochemical parameters, such as moisture, acidity, and temperature. Therefore, exploring the association among microbiota (core), physicochemical factors (reference) and flavor compounds (target) has become a key point to clarify the formation mechanism for the flavor quality of Baijiu. Daqu fermentation and liquor fermentation are the two major stages of Baijiu brewing. Daqu, distillers' grains, and pit mud, as the most important fermentation substrates of the microbiota respectively, provide a large number of functional microorganisms related to the flavor components. To this end, we reviewed the relevant research progress of microbiota diversity in different fermentation substrates and the interaction mechanisms among microbiota, physicochemical parameters, and flavor components in this paper. Moreover, a research hypothesis of precise control of the Baijiu fermentation process by building fermentation models based on this is proposed. The key point for this idea is the identification of core microbiota closely associated with the formation of key flavor components by multi-omics technology and the acquisition of culturable strains. With this foundation, fermentation models suitable for different brewing environments will be established by constructing synthetic microbiota, designing mathematical models, and determining key fermentation model parameters. The ultimate goal will be to effectively improve the quality and stability of Baijiu products through model regulation.

Enzyme Activity and Lipogenesis Inhibition by Fermented Grain Using Natural Enzymes

This study aims to compare the effects of three enzyme-rich foods, including one fermented (grain enzyme) and two non-fermented foods (enzyme foods 1 and 2), by investigating their antioxidant, anti-inflammatory, and anti-adipogenic properties. Grain enzyme exhibited the highest radical scavenging activity and was rich in antioxidant components, including total polyphenol and total flavonoid contents. Grain enzyme and enzyme foods 1 and 2 inhibited nitric oxide production by 27, 34, and 17%, respectively, at a concentration of 200 μg/mL in LPS-stimulated macrophages. Among the tested enzymes, grain enzyme demonstrated the strongest inhibition on the expression of inducible nitric oxide synthase (INOS), cyclooxygenase-2 (COX-2), and interleukin (IL)-1β, while Enzyme Food 2 exhibited the most significant suppression of IL-6 mRNA levels. Furthermore, Grain Enzyme demonstrated a stronger inhibitory effect compared to Enzyme Food 1 and 2. Grain Enzyme decreased the mRNA expression of peroxisome proliferator-activated receptor (PPAR)γ, CCAAT/enhancer-binding protein (C/EBP)α, and fatty acid-binding protein (FABP)4 by 28, 21, and 30%, respectively, at a concentration of 400 μg/mL. In summary, fermented grain enzymes outperformed non-fermented enzymes in suppressing inflammation and adipogenesis. This study highlights the anti-inflammatory and anti-adipogenic effects of grain enzyme, suggesting its potential as a valuable dietary supplement for managing metabolic disorders.

Characterization of microbial communities in seven wetlands with different anthropogenic burden using Next Generation Sequencing in Bogotá, Colombia

Wetlands represent key ecosystems due to their remarkable biodiversity, ecological functions and multiple ecosystem services provided. In Colombia, there are 31,702 wetlands, 13 of which are in Bogotá, capital of the country. Despite the fundamental socioecological support of these aquatic ecosystems, a tremendous loss and degradation of these ecosystems has been observed due to anthropogenic perturbations. Therefore, the aim of this study was to describe the status of seven Bogotá wetlands with variable anthropogenic interventions by measuring organoleptic, physicochemical, and microbiological parameters, using commercial kits, highly sensitive equipment, and next-generation sequencing of the 16S- and 18S-rRNA genes. Our findings describe the status of seven wetlands with different anthropogenic burden in Bogotá-Colombia where physicochemical and microbiology signals of contamination were observed. Additionally, some profiles in the composition of the microbial communities, together with certain physicochemical characteristics, may represent an insight into the environmental dynamics, where Beta Proteobacteria such as Malikia represent a potential keystone in aquatic ecosystems impacted by wastewater effluent discharges; the presence of nitrates and phosphates explain the abundance of bacteria capable of oxidizing these compounds, such as Polynucleobacter. Moreover, the presence of specific prokaryotic and eukaryotic organisms, such as Clostridium, Cryptococcus, Candida, and Naegleria, reported in one or more of the wetlands assessed here, could represent a possible pathogenic risk for human and animal health. This study performed a complete evaluation of seven Bogotá wetlands with different anthropogenic impacts for the first time, and our findings emphasize the importance of maintaining continuous monitoring of these water bodies given their remarkable ecological importance and potential spill-over of several pathogens to humans and animals.

Comparative analysis of the microbiotas and physicochemical properties inside and outside medium-temperature Daqu during the fermentation and storage

Medium-temperature Daqu (MT-Daqu), a saccharification-fermentation agent and aroma-producing agent, is used to produce Chinese strong-flavor Baijiu. Many related studies have been published; however, less is known about microbial community and quality properties inside and outside the MT-Daqu from fermentation to storage. Here, along with determining the physicochemical index, the microbial community of MT-Daqu was investigated using both culture-dependent and culture-independent methods during 31 days of fermentation and 4 months of storage. Volatile compounds of mature MT-Daqu were analyzed using headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC–MS). The results indicated obvious variation in the microbial community due to the changes in environmental conditions, and the physicochemical indices shifted from fluctuations in the fermentation period to relative stability after storage for 3 months. Moreover, the microbial counts and physicochemical indices of the inner layers of MT-Daqu differed from those of the outer layers. The dominant communities, including the bacterial phyla Firmicutes, Proteobacteria, and Actinobacteria and the fungal phyla Ascomycota and Mucoromycota, showed different abundances in the two parts of the mature MT-Daqu, and different microbial communities were enriched in both parts. Additionally, pyrazines and alcohols were the most abundant volatile aroma compounds in the mature MT-Daqu.

Fermentation of Cereals and Legumes: Impact on Nutritional Constituents and Nutrient Bioavailability

Fermented food products, especially those derived from cereals and legumes are important contributors to diet diversity globally. These food items are vital to food security and significantly contribute to nutrition. Fermentation is a process that desirably modifies food constituents by increasing the palatability, organoleptic properties, bioavailability and alters nutritional constituents. This review focuses on deciphering possible mechanisms involved in the modification of nutritional constituents as well as nutrient bioavailability during the fermentation of cereals and legumes, especially those commonly consumed in developing countries. Although modifications in these constituents are dependent on inherent and available nutrients in the starting raw material, it was generally observed that fermentation increased these nutritive qualities (protein, amino acids, vitamins, fats, fatty acids, etc.) in cereals and legumes, while in a few instances, a reduction in these constituents was noted. A general reduction trend in antinutritional factors was also observed with a corresponding increase in the nutrient bioavailability and bioaccessibility. Notable mechanisms of modification include transamination or the synthesis of new compounds during the fermentation process, use of nutrients as energy sources, as well as the metabolic activity of microorganisms leading to a degradation or increase in the level of some constituents. A number of fermented products are yet to be studied and fully understood. Further research into these food products using both conventional and modern techniques are still required to provide insights into these important food groups, as well as for an overall improved food quality, enhanced nutrition and health, as well as other associated socioeconomic benefits.

Ecological succession and functional characteristics of lactic acid bacteria in traditional fermented foods

Fermented foods are important parts of traditional food culture with a long history worldwide. Abundant nutritional materials and open fermentation contribute to the diversity of microorganisms, resulting in unique product quality and flavor. Lactic acid bacteria (LAB), as important part of traditional fermented foods, play a decisive role in the quality and safety of fermented foods. Reproduction and metabolic of microorganisms drive the food fermentation, and microbial interaction plays a major role in the fermentation process. Nowadays, LAB have attracted considerable interest due to their potentialities to add functional properties to certain foods or as supplements along with the research of gut microbiome. This review focuses on the characteristics of diversity and variability of LAB in traditional fermented foods, and describes the principal mechanisms involved in the flavor formation dominated by LAB. Moreover, microbial interactions and their mechanisms in fermented foods are presented. They provide a theoretical basis for exploiting LAB in fermented foods and improving the quality of traditional fermented foods. The traditional fermented food industry should face the challenge of equipment automation, green manufacturing, and quality control and safety in the 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.

Modelling and predicting population of core fungi through processing parameters in spontaneous starter (Daqu) fermentation

Traditional fermented foods are usually produced by spontaneous fermentation with multiple microorganisms. Environmental factors play important roles in microbial succession. However, it is still unclear how the processing parameters regulate the microbiota during fermentation. Here, we reveal the effects of processing parameters on the core microbiota in spontaneous fermentation of Chinese liquor starter. Rhizopus, Pichia, Wickerhamomyces, Saccharomycopsis, Aspergillus and Saccharomyces were identified as core microbiota using amplicon sequencing and metaproteomics analysis. Fermentation moisture gradually decreased from 34.8% to 14.2%, and fermentation temperature varied between 17.0 °C and 35.3 °C during the fermentation. Mantel test showed that fermentation moisture (P < 0.001) and fermentation temperature (P < 0.05) significantly affected the core microbiota. Moreover, structural equation modelling analysis indicated that fermentation moisture (P < 0.001) and fermentation temperature (P < 0.001) were respectively influenced by the processing parameters, room humidity and room temperature. The succession of Rhizopus, Pichia, Wickerhamomyces, Saccharomycopsis and Aspergillus were significantly affected by room humidity (P < 0.05), and the succession of Saccharomyces was significantly affected by room temperature (P < 0.001). Further, models were constructed to predict the population of core microbiota by room humidity and room temperature, using Gaussian process regression and linear regression (P < 0.05). This work would be beneficial for regulating microorganisms via controlling processing parameters in spontaneous food fermentations.

Analysis of soil respiration and influencing factors in a semiarid dune-meadow cascade ecosystem

The characteristics of soil respiration (R_s) in semiarid regions are important with regard to the carbon cycle of complex underlying surfaces and estimation of carbon emissions from regional ecosystems. During the growing season (May-September 2016), in situ observations of R_s were obtained concurrently with measurements of soil bacteria (B_s), soil moisture (M_s), and soil temperature (T_s) at depths of 0-10 cm, in a dune-meadow cascade ecosystem. Results showed that R_s differences among the various ecosystems were significant (P < 0.01), the intensity of R_s in meadows was twice stronger than that in dunes. The average values of R_s presenting a declined trend follows MPA (11.19 μmol m^-2 s^-1) > MAF (7.75) > SSG (6.78) > SMAH (5.02) > SFAH (4.8) > FLC (4.28) > SBG (3.09). An extremely significant (p < 0.01) positive correlated power relationship can be found between R_s and B_s, which could explain 62.41%-86.56% of the variation in R_s in the various ecosystems. Field capacity and the saturated water content were the key demarcation points for the interactive relationship between R_s and M_s, which showing a significant (P < 0.05) positive correlated power relationship in dunes, in contrast, it presenting a significant (P < 0.05) negative correlated exponential relationship in meadows. R_s was positively exponentially correlated with T_s, significant (P < 0.05) in meadows and nonsignificant (P > 0.05) in dunes. Future research should be strengthened to consider multiple growing seasons experiencing various climatic conditions for accurate estimation of terrestrial carbon emissions in arid and semiarid ecosystems.

Bio-augmented effect of Bacillus amyloliquefaciens and Candida versatilis on microbial community and flavor metabolites during Chinese horse bean-chili-paste fermentation

Chinese horse bean-chili-paste (CHCP), a fermented condiment in China, is traditionally manufactured through naturally spontaneous semi-solid fermentation procedures without intentionally inoculated microorganisms. The aim of this study was to investigate the effect on microbiota and quality variations during CHCP fermentation by inoculation of selected autochthonous microorganisms Bacillus amyloliquefaciens and Candida versatilis. The results showed that relative abundance of Bacillus in the samples inoculated with B. amyloliquefaciens were increased from about 0.6% to almost 25%, and the batches bio-augmented with C. versatilis exhibited clearly 0.7 Lg copies/g higher biomass than that of the other samples. By bio-augmentation, six enzyme activities, namely acid protease, leucine aminopeptidase, α-amylase, cellulose, β-glucosidase and esterase, were considerably enhanced. As a result, inoculation of these two strains exhibited significant effect on the volatile profiles of CHCP. B. amyloliquefaciens herein was found to contribute mainly to the accumulation of acids, sulfur-containing compounds and pyrazines, whereas C. versatilis was considerably associated with the formation of alcohols, esters and phenols. This study proved that combination of B. amyloliquefaciens and C. versatilis could obtain more extensive aroma profiles, especially for the enrichment of miso-like and fruity flavors, which could provide a guideline for the tailored control of CHCP fermentation process.

Microbial Communities' Characterization in Urban Recreational Surface Waters Using Next Generation Sequencing

Microbial communities in surface waters used for recreational purposes are indicators of contamination and risk of contact with human pathogens. Hence, monitoring microbial communities in recreational waters is important for potential public health threats to humans. Such monitoring is rare in Colombia, even in its capital, Bogotá, the most populous city in the country. This city encompasses metropolitan and linear parks with recreational water bodies that are used frequently by the public, and the presence of pathogens can compromise the health of the citizens. Therefore, we examined the bacterial, and eukaryotic communities in urban recreational lakes (URL) in four metropolitan parks in Bogotá, Colombia. Samples from four metropolitan parks (Los Novios, Simon Bolivar, El Tunal, and Timiza) and one stream contaminated with sewage from a linear park (El Virrey) were collected. We used amplicon next-generation sequencing of the 16S-rRNA gene and 18S-rRNA gene to characterize microbial communities followed by bioinformatics analyses. In addition, general water quality parameters-pH, hardness, acidity, alkalinity, dissolved oxygen, and nitrites-were recorded using a commercial kit. Genera of pathogens, including Legionella, Pseudomonas, Mycobacterium, Candida, and Naegleria, were found in lake waters. The stream El Virrey was, however, the only surface water that showed an abundance of fecal bacteria, often associated with low oxygen concentrations. All water bodies showed a predominance of fungal phyla, except for the lake at Timiza. This lake showed the highest pH, and its ecological dynamics are likely different from other water bodies. Likewise, some URLs displayed a greater abundance of cyanobacteria, including toxin-producing species. Algal genera associated with eutrophication were predominant among primary producing microorganisms. This study shows for the first time the description of the bacterial and eukaryotic communities of some URLs and a stream in Bogotá. The URLs and the stream harbored various pathogens that might pose a risk to the citizen's health.

The effects of dynamic bacterial succession on the flavor metabolites during Baijiu fermentation

The succession of microbial community significantly affect the flavor formation of traditional fermented foods and beverages. Chinese liquor (Baijiu) fermentation is a typical spontaneous solid-state fermentation process driven by natural microbiota. The type of process used to make liquor-craft or industrial-alters the operational environment and the aromatic qualities of the product contributed by various microbial consortia. But differences in microbial community assembly and temporal succession are often overlooked. In this study, we investigated bacterial community dynamics, substrate consumption, and metabolite production during both craft and industrial liquor-making processes (CLP and ILP, respectively). We found that the compositions of bacterial communities were different, even though no significant difference (p > 0.05) was observed in bacterial species between CLP and ILP at the beginning of fermentation. During ILP, glucose was used more rapidly by microflora, leading in turn to a higher ethanol production rate during the early stage of fermentation. The higher rate of ethanol production in ILP shortened the lifetime of bacteria such as Weissella, Pediococcus, Leuconostoc, and Bacillus during the early stage of fermentation. Lactobacillus sp. became dominant earlier in ILP than in CLP. Finally, the change in bacterial community dynamics led to changes in aroma compounds. Using CLP and ILP as a model system, our results illustrate the dynamic nature of Baijiu fermentations and microbial succession patterns therein. This can be applied to optimize the fermentation processes and flavors attributes of this and other fermented foods.

Daqu microbiota exhibits species-specific and periodic succession features in Chinese baijiu fermentation process

Daqu, a brick-shaped product spontaneously fermented under an open environment, has been regarded as the starter of fermentation, raw enzyme preparation and raw materials for baijiu production. However, its contribution in baijiu fermentation has not been fully elaborated yet. Here, the effects of daqu microbiota on baijiu fermentation were investigated under both field-scale and lab-scale conditions. In field-scale baijiu fermentation, the dominant daqu microbes (average relative abundance>10.0%), including unclassified_Leuconostocaceae, Thermoascus, and Thermomyces, tended to dominate the early stage (0-7 d). However, the rare daqu microbes (average relative abundance <0.1%, e.g., Kazachstania) tended to dominate the middle and late stages (11-40 d). In addition, some genera showed differences in species diversity between daqu and fermented grains. The average relative abundance of Lactobacillus was over 75% during baijiu fermentation, and most of them were affiliated with Lactobacillus acetotolerans, while Lactobacillus crustorum dominated the Lactobacillus OTUs in daqu. The similar patterns were also observed during lab-scale baijiu fermentation. The results of function prediction showed the enriched metabolic pathways were associated with glycolysis and long-chain fatty acid esters in baijiu fermentation. These results improved the understanding of daqu microbiota function during baijiu fermentation and provided a basic theory to support the regulation of baijiu production.

Nutritional and Functional Properties of Fermented Mixed Grains by Solid-State Fermentation with Bacillus amyloliquefaciens 245

Fermented foods have several advantages, including increased nutritional value, improved bioavailability, and functional health properties. We examined that these outcomes were also observed in fermented mixed grains (FMG) containing wheat germ, wheat bran, oats, brown rice, barley, quinoa, and lentils following solid-state fermentation (SSF) by Bacillus amyloliquefaciens 245. The metabolic profile during fermentation was screened using capillary electrophoresis time-of-flight mass spectrometry (CE-TOF-MS). The amino acids were quantitatively measured for the validation of the changes in metabolites. The activity of enzymes (e.g., amylase, protease, and fibrinolysis) and antioxidant capacity was also assessed to elucidate the functionality of FMG. The essential amino acid contents gradually increased as fermentation progressed. As the metabolites involved in the urea cycle and polyamine pathway were changed by fermentation, arginine was used as a substance to produce citrulline, ornithine, and agmatine. FMG showed dramatic increases in enzyme activity. FMG incubated for 36 h also displayed higher total phenolic contents and free radical scavenging ability than MG. The data suggest that FMG produced by Bacillus amyloliquefaciens 245 possess improved nutritional and functional quality, leading to their potential use as dietary supplements.

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.

Synergistic Effect of Multiple Saccharifying Enzymes on Alcoholic Fermentation for Chinese Baijiu Production

Chinese Jiuqu (fermentation starter) provides saccharifying enzymes for baijiu (Chinese liquor) fermentation, which undergoes a simultaneous saccharification and fermentation process. However, the key saccharifying enzymes associated with alcoholic fermentation from Jiuqu and their effects on ethanol production remain poorly understood. In this study, we identified 51 carbohydrate hydrolases in baijiu fermentation by metaproteomics analysis. Through source-tracking analysis, approximately 80% of carbohydrate hydrolases in the baijiu fermentation were provided by Jiuqu Among these enzymes, alpha-amylase (EC 3.2.1.1) and glucoamylase (EC 3.2.1.3), from Aspergillus, Rhizomucor, and Rhizopus, were positively related to starch hydrolysis and ethanol production, indicating that they were the key saccharifying enzymes associated with alcoholic fermentation in the baijiu fermentation. Moreover, a combined mixture of alpha-amylase and glucoamylase (in a ratio of 1:6, wt/wt) enhanced ethanol production in a simulative baijiu fermentation under laboratory conditions. This result revealed a synergistic effect of multiple saccharifying enzymes on ethanol production in baijiu fermentation. Our study provides a potential approach to improve the efficiency of saccharification and alcoholic fermentation by optimizing the profile of saccharifying enzymes for fermentation of baijiu and other beverages.IMPORTANCE Jiuqu starter provides enzymes to the simultaneous saccharification and fermentation process of baijiu (Chinese liquor) production; however, the key saccharifying enzymes associated with alcoholic fermentation from Jiuqu and their effects on ethanol production remain unclear. We confirmed that Jiuqu was the main source of carbohydrate hydrolases for baijiu fermentation and identified two types of saccharifying enzymes from multiple microbes as the key enzymes associated with alcoholic fermentation. Moreover, a proper combination of multiple saccharifying enzymes could enhance ethanol production in baijiu fermentation. This combination provides an approach to optimize the profile of saccharifying enzymes for enhancing ethanol production in baijiu and other food fermentations.

Screening of tea saponin-degrading strain to degrade the residual tea saponin in tea seed cake

Although tea seed cake (TSC) possesses high nutritional value, its high content of tea saponin (TS) limits its potential as feed. This study aimed to degrade TS in TSC by saponin-degrading strain and used a multistrains fermentation method to improve its nutritional value and palatability. Three saponin-degrading strains were isolated from Oleum Camelliae mill soil and identified as Citrobacter sp. FCTS301, Pantoea sp. FCTS302, and Enterobacter sp. FCTS303. Single-factor experiment showed that Citrobacter sp. FCTS301 had the highest degradation rate of TS. Response surface analysis for Citrobacter sp. FCTS301 indicated that the optimum culture conditions were as follows: initial pH of 7.2, culture temperature of 34.2 °C, inoculation amount of 7.3%, the agitation rate of 150 rpm, and the TS concentration of 10.0 g/L. Under these conditions, the maximum degradation rate was 82.6%. The fermentation process of TSC was obtained by a multistrains fermentation experiment. Considering the protein content, crude fiber degradation rate, and TS degradation rate of each group, the optimum inoculum amount of strains included Citrobacter sp. FCTS301, Aspergillus oryzae NCUF414, Saccharomyces cersvisiae NCUF306.5, and Lactobacillus plantarum NCUF201.1(5%, 0.5%, 1.0%, and 1.5%). After TS was degraded efficiently, fermented TSC can be presumed a potential feed raw material.

Exploring functional core bacteria in fermentation of a traditional Chinese food, Aspergillus-type douchi

Douchi is a type of traditional Chinese flavoring food that has been used for thousands of years and is produced by multispecies solid-state fermentation. However, the correlation between the flavor, the microbiota, and the functional core microbiota in Aspergillus-type douchi fermentation remains unclear. In this study, Illumina MiSeq sequencing and chromatography were used to investigate the bacterial community and flavor components in Aspergillus-type douchi fermentation. The dominant phyla were Firmicutes, Proteobacteria, and Actinobacteria, and the dominant genera were Weissella, Bacillus, Anaerosalibacter, Lactobacillus, Staphylococcus, and Enterococcus. A total of 58 flavor components were detected during fermentation, including two alcohols, 14 esters, five pyrazines, three alkanes, four aldehydes, three phenols, six acids, and five other compounds. Bidirectional orthogonal partial least square modeling showed that Corynebacterium_1, Lactococcus, Atopostipes, Peptostreptococcus, norank_o__AKYG1722, Truepera, Gulosibacter, norank_f__Actinomycetaceae, and unclassified_f__Rhodobacteraceae are the functional core microbiota responsible for the formation of the flavor components during douchi fermentation. This is the first study to investigate the functional core microbiota in douchi fermentation using Illumina MiSeq sequencing and chromatographic techniques. Our findings extend our understanding of the relationships between flavor, the microbiota, and the functional core microbiota during Aspergillus-type douchi fermentation.

Comparison of microbial community and metabolites in spontaneous fermentation of two types Daqu starter for traditional Chinese vinegar production

Daqu starter, an important saccharifying and fermenting agent for the brewing process of traditional vinegar, is manufactured by spontaneous solid-state fermentation which routinely undergoes low or medium incubation temperature. Previous studies have demonstrated that the temperature plays a pivotal role in Daqu quality. Hence, to explore the feasibility of high temperature fermentation applied in the vinegar Daqu brewing and provide guidelines of controlling environmental parameters in traditional vinegar industries, the microbial community and metabolites of vinegar Daqu during medium-temperature and high-temperature fermentation processes (namely, MTFP and HTFP) were compared. The results indicated that the glucoamylase activity, amylase activity and microbial community showed no significant difference in the end of two batches (P > 0.05). Enterobacteriales, Lactobacillales, Bacillales, Saccharomycetales and Mucorales were the dominant orders during MTFP and HTFP. Redundancy analysis revealed that incubation temperature showed positive correlation with the microbial composition from days 3-14 of the fermentation process and was positively associated with the predominant phylotypes of Bacillales, Mucorales, Xanthomonadales and Rickettsiales. The acidity and moisture showed major correlations with microbial composition on day 1 of MTFP and were positively related with the predominant phylotypes of Mucorales and Lactobacillales at the order level. Moreover, higher relative contents of all volatiles were shown in the end of HTFP (13.91 mg/100 g Daqu) compared to MTFP (10.01 mg/100 g Daqu). This work illustrates high temperature (approximately 60°C) fermentation is promising to improve the vinegar Daqu flavor and shall likely contribute to preferably make traditional Daqu by modulating steerable environmental parameters.

Unraveling the Contribution of High Temperature Stage to Jiang-Flavor Daqu, a Liquor Starter for Production of Chinese Jiang-Flavor Baijiu, With Special Reference to Metatranscriptomics

Jiang-flavor (JF) daqu is a liquor starter used for production of JF baijiu, a well-known distilled liquor in China. Although a high temperature stage (70°C) is necessary for qualifying JF daqu, little is known regarding its active microbial community and functional enzymes, along with its role in generating flavor precursors for JF baijiu aroma. In this investigation, based on metatranscriptomics, fungi, such as Aspergillus and Penicillium, were identified as the most active microbial members and 230 carbohydrate-active enzymes were identified as potential saccharifying enzymes at 70°C of JF daqu. Notably, most of enzymes in identified carbohydrate and energy pathways showed lower expression levels at 70°C of JF daqu than those at the high temperature stage (62°C) of Nong-flavor (NF) daqu, indicating lowering capacities of saccharification and fermentation by high temperature stage. Moreover, many enzymes, especially those related to the degradation of aromatic compounds, were only detected with low expression levels at 70°C of JF daqu albeit not at 62°C of NF daqu, indicating enhancing capacities of generating special trace aroma compounds in JF daqu by high temperature stage. Additionally, most of enzymes related to those capacities were highly expressed at 70°C by fungal genus of Aspergillus, Coccidioides, Paracoccidioides, Penicillium, and Rasamsonia. Therefore, this study not only sheds light on the crucial functions of high temperature stage but also paves the way to improve the quality of JF baijiu and provide active community and functional enzymes for other fermentation industries.

Daqu Fermentation Selects for Heat-Resistant Enterobacteriaceae and Bacilli

Daqu is a spontaneous solid-state cereal fermentation used as saccharification and starter culture in Chinese vinegar and liquor production. The evolution of microbiota in this spontaneous fermentation is controlled by the temperature profile, which reaches temperatures from 50 to 65°C for several days. Despite these high temperatures, mesophilic Enterobacteriaceae (including Cronobacter) and bacilli are present throughout Daqu fermentation. This study aimed to determine whether Daqu spontaneous solid-state fermentation selects for heat-resistant variants of these organisms. Heat resistance in Enterobacteriaceae is mediated by the locus of heat resistance (LHR). One LHR-positive strain of Kosakonia cowanii was identified in Daqu, and it exhibited higher heat resistance than the LHR-negative K. cowanii isolated from malted oats. Heat resistance in Bacillus endospores is mediated by the spoVA ^2mob operon. Out of 10 Daqu isolates of the species Bacillus licheniformis, Brevibacillus parabrevis, Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus velezensis, 5 did not contain spoVA ^2mob, 3 contained one copy, and 2 contained two copies. The presence and copy number of the spoVA ^2mob operon increased the resistance of spores to treatment with 110°C. To confirm the selection of LHR- and spoVA ^2mob-positive strains during Daqu fermentation, the copy numbers of these genetic elements in Daqu samples were quantified by quantitative PCR (qPCR). The abundance of LHR and the spoVA ^2mob operon in community DNA relative to that of total bacterial 16S rRNA genes increased 3-fold and 5-fold, respectively, during processing. In conclusion, culture-dependent and culture-independent analyses suggest that Daqu fermentation selects for heat-resistant Enterobacteriaceae and bacilli.IMPORTANCE Daqu fermentations select for mobile genetic elements conferring heat resistance in Enterobacteriaceae and bacilli. The locus of heat resistance (LHR), a genomic island conferring heat resistance in Enterobacteriaceae, and the spoVA ^2mob operon, conferring heat resistance on bacterial endospores, were enriched 3- to 5-fold during Daqu fermentation and maturation. It is therefore remarkable that the LHR and the spoVA ^2mob operon are accumulated in the same food fermentation. The presence of heat-resistant Kosakonia spp. and Bacillus spp. in Daqu is not of concern for food safety; however, both genomic islands are mobile and transferable to pathogenic bacteria or toxin-producing bacteria by horizontal gene transfer. The identification of the LHR and the spoVA ^2mob operon as indicators of fitness of Enterobacteriaceae and bacilli in Daqu fermentation provides insights into environmental sources of heat-resistant organisms that may contaminate the food supply.

Specific Volumetric Weight-Driven Shift in Microbiota Compositions With Saccharifying Activity Change in Starter for Chinese Baijiu Fermentation

Chinese starter Jiuqu, traditionally produced by spontaneous fermentation and always squeezed into bricks, serves as a vital saccharifying agent for simultaneous saccharification and fermentation of Chinese Baijiu. It is important to reveal the key saccharifying microbiota and the driving force to improve the quality of Jiuqu. Here we studied the compositions of the microbiota by high-throughput amplicons sequencing analysis in Jiuqu, and revealed eight bacterial and seven fungal genera as the dominant community members. Among them, Lactobacillus, Aspergillus, Pichia, Saccharomyces, Rhizopus were the main contributors of proteins by metaproteomics analysis. Whereas, only Lactobacillus, Pichia, Rhizopus appeared as key actors for saccharification by secreting three glycosidases and two glycosyltransferases, and it indicated they were the key saccharifying microbiota in Jiuqu. Especially, Rhizopus secreted the most abundant glucoamylase. Interestingly, these three active genera significantly decreased and the key saccharifying enzymes were down-expressed, when Jiuqu was produced in diffused shape with a low volumetric weight. Rhizopus microsporus, the main producer of glucoamylase, was positively correlated with volumetric weight of Jiuqu. It indicated volumetric weight was the major driving force of the key saccharifying microbiota in Jiuqu. This work provides deep insights of key saccharifying microbiota, and indicates the main driving force for the key microbe. Furthermore, this finding can contribute to the improvement of saccharifying agent for food fermentation.

Evaluating the microbial ecology and metabolite profile in Kazak artisanal cheeses from Xinjiang, China

Kazak artisanal cheese is one of the famous fermented food in Uighur Autonomy Region of Xinjiang, China. However, the microbial ecology in Kazak artisanal cheeses across different regions is unclear. In this study, we determined the microbial community composition through amplicon sequencing and measured the flavor profile of 10 cheese samples from different regions of Xinjiang. The associations between microbial communities, flavors and environmental factors were examined by redundancy analysis and Monte Carlo permutation test. Cheeses from different regions had different microbial communities, which was mainly reflected in the relative abundance of Lactobacillus, Streptococcus, Issatchenkia, Debaryomyces and Kluyveromyces. In addition, Pichia and Torulaspora were also the key microbial groups, according to the high relative abundance and large co-occurrence incidence in the correlation network. Using the microbe-metabolites correlation analysis, the major flavor-producing taxa were identified as Kluyveromyces, Anoxybacillus, Torulaspora, Lactobacillus, Streptococcus and Dipodascus. Environmental factors accounted for the majority of the microbial community variations, 88.54% for bacteria and 75.71% for fungi. Compared to physico-chemical factors (temperature, moisture, and pH), geographical factors (longitude, latitude and elevation) had a stronger effect on microbial communities in cheese samples from different regions of Xinjiang.

Succession sequence of lactic acid bacteria driven by environmental factors and substrates throughout the brewing process of Shanxi aged vinegar

Lactic acid bacteria (LAB) are essential microbiota for the fermentation and flavor formation of Shanxi aged vinegar, a famous Chinese traditional cereal vinegar that is manufactured using open solid-state fermentation (SSF) technology. However, the dynamics of LAB in this SSF process and the underlying mechanism remain poorly understood. Here, the diversity of LAB and the potential driving factors of the entire process were analyzed by combining culture-independent and culture-dependent methods. Canonical correlation analysis indicated that ethanol, acetic acid, and temperature that result from the metabolism of microorganisms serve as potential driving factors for LAB succession. LAB strains were periodically isolated, and the characteristics of 57 isolates on environmental factor tolerance and substrate utilization were analyzed to understand the succession sequence. The environmental tolerance of LAB from different stages was in accordance with their fermentation conditions. Remarkable correlations were identified between LAB growth and environmental factors with 0.866 of ethanol (70 g/L), 0.756 of acetic acid (10 g/L), and 0.803 of temperature (47 °C). More gentle or harsh environments (less or more than 60 or 80 g/L of ethanol, 5 or 20 g/L of acetic acid, and 30 or 55 °C temperature) did not affect the LAB succession. The utilization capability evaluation of the 57 isolates for 95 compounds proved that strains from different fermentation stages exhibited different predilections on substrates to contribute to the fermentation at different stages. Results demonstrated that LAB succession in the SSF process was driven by the capabilities of environmental tolerance and substrate utilization.

The structural and functional contributions of β-glucosidase-producing microbial communities to cellulose degradation in composting

BACKGROUND

Compost habitats sustain a vast ensemble of microbes that engender the degradation of cellulose, which is an important part of global carbon cycle. β-Glucosidase is the rate-limiting enzyme of degradation of cellulose. Thus, analysis of regulation of β-glucosidase gene expression in composting is beneficial to a better understanding of cellulose degradation mechanism. Genetic diversity and expression of β-glucosidase-producing microbial communities, and relationships of cellulose degradation, metabolic products and the relative enzyme activity during natural composting and inoculated composting were evaluated.

RESULTS

Compared with natural composting, adding inoculation agent effectively improved the degradation of cellulose, and maintained high level of the carboxymethyl cellulose (CMCase) and β-glucosidase activities in thermophilic phase. Gene expression analysis showed that glycoside hydrolase family 1 (GH1) family of β-glucosidase genes contributed more to β-glucosidase activity in the later thermophilic phase in inoculated compost. In the cooling phase of natural compost, glycoside hydrolase family 3 (GH3) family of β-glucosidase genes contributed more to β-glucosidase activity. Intracellular β-glucosidase activity played a crucial role in the regulation of β-glucosidase gene expression, and upregulation or downregulation was also determined by extracellular concentration of glucose. At sufficiently high glucose concentrations, the functional microbial community in compost was altered, which may contribute to maintaining β-glucosidase activity despite the high glucose content.

CONCLUSION

This research provides an ecological functional map of microorganisms involved in carbon metabolism in cattle manure-rice straw composting. The performance of the functional microbial groups in the two composting treatments is different, which is related to the cellulase activity and cellulose degradation, respectively.

The process-related dynamics of microbial community during a simulated fermentation of Chinese strong-flavored liquor

BACKGROUND

Famous Chinese strong-flavored liquor (CSFL) is brewed by microbial consortia in a special fermentation pit (FT). However, the fermentation process was not fully understood owing to the complicate community structure and metabolism. In this study, the process-related dynamics of microbial communities and main flavor compounds during the 70-day fermentation process were investigated in a simulated fermentation system.

RESULTS

A three-phase model was proposed to characterize the process of the CSFL fermentation. (i) In the early fermentation period (1-23 days), glucose was produced from macromolecular carbohydrates (e.g., starch). The prokaryotic diversity decreased significantly. The Lactobacillaceae gradually predominated in the prokaryotic community. In contrast, the eukaryotic diversity rose remarkably in this stage. Thermoascus, Aspergillus, Rhizopus and unidentified Saccharomycetales were dominant eukaryotic members. (ii) In the middle fermentation period (23-48 days), glucose concentration decreased while lactate acid and ethanol increased significantly. Prokaryotic community was almost dominated by the Lactobacillus, while eukaryotic community was mainly comprised of Thermoascus, Emericella and Aspergillus. (iii) In the later fermentation period (48-70 days), the concentrations of ethyl esters, especially ethyl caproate, increased remarkably.

CONCLUSIONS

The CSFL fermentation could undergo three stages: saccharification, glycolysis and esterification. Saccharomycetales, Monascus, and Rhizopus were positively correlated to glucose concentration (P < 0.05), highlighting their important roles in the starch saccharification. The Lactobacillaceae, Bacilli, Botryotinia, Aspergillus, unidentified Pleosporales and Capnodiales contributed to the glycolysis and esterification, because they were positively correlated to most organic acids and ethyl esters (P < 0.05). Additionally, four genera, including Emericella, Suillus, Mortierella and Botryotinia, that likely played key roles in fermentation, were observed firstly. This study observed comprehensive dynamics of microbial communities during the CSFL fermentation, and it further revealed the correlations between some crucial microorganisms and flavoring chemicals (FCs). The results from this study help to design effective strategies to manipulate microbial consortia for fermentation process optimization in the CSFL brew practice.

The distribution of active β-glucosidase-producing microbial communities in composting

The composting ecosystem is a suitable source for the discovery of novel microorganisms and secondary metabolites. Cellulose degradation is an important part of the global carbon cycle, and β-glucosidases complete the final step of cellulose hydrolysis by converting cellobiose to glucose. This work analyzes the succession of β-glucosidase-producing microbial communities that persist throughout cattle manure - rice straw composting, and evaluates their metabolic activities and community advantage during the various phases of composting. Fungal and bacterial β-glucosidase genes belonging to glycoside hydrolase families 1 and 3 (GH1 and GH3) amplified from DNA were classified and gene abundance levels were analyzed. The major reservoirs of β-glucosidase genes were the fungal phylum Ascomycota and the bacterial phyla Firmicutes, Actinobacteria, Proteobacteria, and Deinococcus-Thermus. This indicates that a diverse microbial community utilizes cellobiose. The succession of dominant bacteria was also detected during composting. Firmicutes was the dominant bacteria in the thermophilic phase of composting; there was a shift to Actinomycetes in the maturing stage. Proteobacteria accounted for the highest proportions during the heating and thermophilic phases of composting. By contrast, the fungal phylum Ascomycota was a minor microbial community constituent in thermophilic phase of composting. Combined with the analysis of the temperature, cellulose degradation rate and the carboxymethyl cellulase and β-glucosidase activities showed that the bacterial GH1 family β-glucosidase genes make greater contribution in cellulose degradation at the later thermophilic stage of composting. In summary, even GH1 bacteria families β-glucosidase genes showing low abundance in DNA may be functionally important in the later thermophilic phase of composting. The results indicate that a complex community of bacteria and fungi expresses β-glucosidases in compost. Several β-glucosidase-producing bacteria and fungi identified in this study may represent potential indicators of composting in cellulose degradation.

Insights into the microbial diversity and community dynamics of Chinese traditional fermented foods from using high-throughput sequencing approaches

Chinese traditional fermented foods have a very long history dating back thousands of years and have become an indispensable part of Chinese dietary culture. A plethora of research has been conducted to unravel the composition and dynamics of microbial consortia associated with Chinese traditional fermented foods using culture-dependent as well as culture-independent methods, like different high-throughput sequencing (HTS) techniques. These HTS techniques enable us to understand the relationship between a food product and its microbes to a greater extent than ever before. Considering the importance of Chinese traditional fermented products, the objective of this paper is to review the diversity and dynamics of microbiota in Chinese traditional fermented foods revealed by HTS approaches.

Characterization of the Typical Potent Odorants in Chinese Roasted Sesame-like Flavor Type Liquor by Headspace Solid Phase Microextraction-Aroma Extract Dilution Analysis, with Special Emphasis on Sulfur-Containing Odorants

The aroma profile of Chinese roasted sesame-like flavor type liquor was investigated by means of headspace solid phase microextraction-aroma extract dilution analysis (HS-SPME-AEDA). Sixty-three odor-active regions were detected by HS-SPME-AEDA with flavor dilution (FD) factors >5, and 58 of these were further identified. Among them, ethyl hexanoate, 2-furfurylthiol, dimethyl trisulfide, 3-methylbutanal, ethyl butanoate, ethyl 2-methylbutanoate, ethyl pentanoate, and ethyl 4-methylpentanoate appeared with the highest FD factors. In particular, eight sulfur-containing odorants were identified to be potentially important to roasted sesame-like flavor type liquor. The concentration of these odor-active compounds was further quantitated by combination of four different quantitative measurements, and 36 odorants had concentrations higher than their corresponding odor thresholds. On the basis of the odor activity values (OAVs), 2-furfurylthiol (OAV 1182), dimethyl trisulfide (OAV 220), β-damascenone (OAV 116), and methional (OAV 99) could be responsible for the unique aroma of roasted sesame-like flavor type liquor. An aroma recombination model prepared by mixing 36 aroma compounds with OAVs >1 showed a good similarity to the aroma of the original roasted sesame-like flavor type liquor. For the first time, 2-furfurylthiol was determined to be a typical potent odorant in roasted sesame-like flavor type liquor by omission study.

High-Throughput Sequencing of Microbial Community Diversity and Dynamics during Douchi Fermentation

Douchi is a type of Chinese traditional fermented food that is an important source of protein and is used in flavouring ingredients. The end product is affected by the microbial community present during fermentation, but exactly how microbes influence the fermentation process remains poorly understood. We used an Illumina MiSeq approach to investigate bacterial and fungal community diversity during both douchi-koji making and fermentation. A total of 181,443 high quality bacterial 16S rRNA sequences and 221,059 high quality fungal internal transcribed spacer reads were used for taxonomic classification, revealing eight bacterial and three fungal phyla. Firmicutes, Actinobacteria and Proteobacteria were the dominant bacterial phyla, while Ascomycota and Zygomycota were the dominant fungal phyla. At the genus level, Staphylococcus and Weissella were the dominant bacteria, while Aspergillus and Lichtheimia were the dominant fungi. Principal coordinate analysis showed structural separation between the composition of bacteria in koji making and fermentation. However, multivariate analysis of variance based on unweighted UniFrac distances did identify distinct differences (p <0.05), and redundancy analysis identified two key genera that are largely responsible for the differences in bacterial composition between the two steps. Staphylococcus was enriched in koji making, while Corynebacterium was enriched in fermentation. This is the first investigation to integrate douchi fermentation and koji making and fermentation processes through this technological approach. The results provide insight into the microbiome of the douchi fermentation process, and reveal a structural separation that may be stratified by the environment during the production of this traditional fermented food.

Effects of initial moisture content of Korean traditional wheat-based fermentation starter nuruk on microbial abundance and diversity

The brewing of makgeolli, one of Korea's most popular alcoholic beverages that is gaining popularity globally, is facilitated by nuruk, a traditional Korean cereal starter. The nuruk microbiome greatly influences the fermentation process as well as the nutritional, hygienic, and aromatic qualities of the product. This study is a continuation of our efforts to examine nuruk biodiversity at a depth previously unattainable. In this study, microfloral dynamics in wheat-based nuruk C, composed of traditional ingredients such as barley, green gram, and wheat and fermented under various internal moisture contents of 20% (C20), 26% (C26), and 30% (C30), was evaluated using 454 pyrosequencing during the 30-day fermentation process. Rarefaction analysis and alpha diversity parameters indicated adequate sampling. C20 showed the greatest fungal richness and diversity, C20 and C26 exhibited similar bacterial richness and diversity, while C30 had low fungal and bacterial richness. Fungal taxonomic assignments revealed that the initial moisture content caused selective enrichment of Aspergillus candidus with a decreasing trend during fermentation, whereas Saccharomycetales sp. exhibited increasing relative abundance with increasing moisture content from day 6 of the fermentation process. Depending on initial moisture level, changes in bacterial communities were also observed in the genera Streptomyces, Bacillus, and Staphylococcus, with decreasing trends whereas Saccharopolyspora exhibited a sigmoidal trend with the highest abundance in C26. These findings demonstrate the possible impact of initial moisture content of nuruk on microfloral richness, diversity, and dynamics; this study is thus a step toward our ultimate goal of enhancing the quality of nuruk.

Proteomic analysis of the adaptative response of Mucor spp. to cheese environment

In the cheese industry context, Mucor species exhibit an ambivalent behavior as some species are essential "technological" organisms of some cheeses while others can be spoiling agents. Previously, we observed that cheese "technological" species exhibited higher optimal growth rates on cheese related matrices than on synthetic media. This growth pattern combined with morphological differences raise the question of their adaptation to cheese. In this study, using a comparative proteomic approach, we described the metabolic pathways of three Mucor strains considered as "technological" or "contaminant" in the cheese environment (M. lanceolatus UBOCC-A-109153, M. racemosus UBOCC-A-109155, M. circinelloides CBS 277-49) as well as a non-cheese related strain (M. endophyticus CBS 385-95). Overall, 15.8 to 19.0% of the proteomes showed a fold change ≥1.6 in Potato Dextrose Agar (PDA) versus Cheese Agar (CA), a cheese mimicking-medium. The 289 differentially expressed proteins identified by LC MS-MS analysis were mostly assigned to energy and amino-acid metabolisms in PDA whereas a higher diversity of biological processes was observed for cheese related strains in CA. Surprisingly, the vast majority (72.9%) of the over-accumulated proteins were different according to the considered medium and strain. These results strongly suggest that the observed better adaptative response of "technological" strains to cheese environment is mediated by species-specific proteins.

BIOLOGICAL SIGNIFICANCE

The Mucor genus consists of a multitude of poorly known species. In the food context, few species are known for their positive role in the production of various food products, including cheese, while others are spoiling agents. The present study focused on the analysis of morphological and proteome differences of various Mucor spp. representative strains known as either positively (hereafter referred as "technological") or negatively (hereafter referred as "contaminant") associated with cheese or non-related to cheese (endophyte) on two different media, a synthetic medium and a cheese-mimicking medium. The main goal was to assess if adaptative traits of "technological" strains to the cheese environment could be identified. This work was based on observations we did in a recently published physiological study (Morin-Sardin et al., 2016). One of the important innovative aspects lies in the use for the first time of an extensive 2-DE approach to compare proteome variations for 4 strains on two different media. Results obtained offered an insight in the metabolic mechanisms associated with growth on a given medium and showed that adaptation to cheese environment is probably supported by species-specific proteins. The obtained data represent an essential step point for more targeted studies at the genomic and transcriptomic levels.

The Bacterial Signature of Leptospermum scoparium (Mānuka) Reveals Core and Accessory Communities with Bioactive Properties

Leptospermum scoparium or mānuka is a New Zealand native medicinal plant that produces an essential oil with antimicrobial properties. This is the first study to investigate the structure and bioactivity of endophytic bacteria in mānuka by using a combination of cultivation-independent (DGGE) and dependent approaches. A total of 23 plants were sampled across three sites. Plants were considered either immature (3-8 years) or mature (>20 years). The endophyte community structure and richness was affected by plant tissue and bacterial communities became more stable and uniform as plant maturity increased. A total of 192 culturable bacteria were recovered from leaves, stems and roots. Some bacterial isolates showed in vitro biocontrol activity against two fungal pathogens, Ilyonectria liriodendri and Neofusicoccum luteum and a bacterial pathogen, Pseudomonas syringae pv. actinidiae. A high proportion of bacterial endophytes could produce siderophores and solubilise phosphate in vitro. Gammaproteobacteria was the most variable class, representing the majority of cultivated bacteria with bioactivity.

Environmental Factors Affecting Microbiota Dynamics during Traditional Solid-state Fermentation of Chinese Daqu Starter

In this study, we investigated the microbiota dynamics during two industrial-scale traditional solid-state fermentation (SSF) processes of Daqu starters. Similar evolution profiles of environmental parameters, enzymatic activities, microbial amounts, and communities were observed during the medium temperature SSF (MTSSF) and low temperature SSF (LTSSF) processes. Orders of Rickettsiales and Streptophyta only dominated the initial 2 days, and Eurotiales only predominated from days 10 to 24, however, phylotypes of Enterobacteriales, Lactobacillales, Bacillales, Saccharomycetales, and Mucorales both prevailed throughout the MTSSF and LTSSF processes. Nevertheless, the pH in MTSSF process on day 5 were 5.28, while in LTSSF process (4.87) significantly lower (P < 0.05). The glucoamylase activities in MTSSF process dropped from 902.71 to 394.33 mg glucose g(-1) h(-1) on days 5 to 24, while significantly lower (P < 0.05) in LTSSF process and decreased from 512.25 to 268.69 mg glucose g(-1) h(-1). The relative abundance of Enterobacteriales and Lactobacillales in MTSSF process constituted from 10.30 to 71.73% and 2.34 to 16.68%, while in LTSSF process ranged from 3.16 to 41.06% and 8.43 to 57.39%, respectively. The relative abundance of Eurotiales in MTSSF process on days 10 to 24 decreased from 36.10 to 28.63%, while obviously higher in LTSSF process and increased from 52.00 to 72.97%. Furthermore, lower bacterial richness but higher fungal richness were displayed, markedly differences in bacterial communities but highly similarities in fungal communities were exhibited, during MTSSF process comparatively to the LTSSF process. Canonical correspondence analysis revealed microbial structure transition happened at thermophilic stages under environmental stress of moisture, pH, acidity, and pile temperature. These profound understanding might help to effectively control the traditional Daqu SSF process by adjusting relevant environmental parameters.