Microbial Volatile Compounds Research Articles

Dynamic Changes and Potential Correlations between Microbial Diversity and Volatile Flavor Compounds in Chinese Medium-Temperature Daqu during Manufacturing.

To investigate the dynamic changes and potential correlations between microbial diversity and volatile organic compounds (VOCs) during Chinese medium-temperature Daqu (MTD) manufacturing at different key stages, in this study, high-throughput sequencing (HTS) and gas chromatography-ion mobility spectrometry (GC-IMS) were employed to analyze the microbial diversity and VOCs of MTD, respectively. The results showed that Weissella, Staphylococcus, Thermoactinomyces, Kroppenstedtia, and Lactobacillus were the dominant bacterial genera, while Aspergillus, Alternaria, Thermoascus, Thermomyces, Wickerhamomyces, and Saccharomyces were the dominant fungal genera. A total of 61 VOCs were detected by GC-IMS, among which, 13 differential VOCs (VIP > 1) were identified, that could be used as potential biomarkers to judge the fermentation stage of MTD. Kroppenstedtia and Saccharopolyspora were positively correlated with 3-methyl-2-butenal and 2,2,4,6,6-pentamethylheptane-D, respectively, and both of these were positively correlated with butanal-D. Acetobacter, Streptomyces, and lactic acid bacteria (LAB) including Leuconostoc, Pediococcus, Weissella, and Lactobacillus were negatively correlated with their associated VOCs, while fungi were generally positively correlated with VOCs. Wickerhamomyces, Saccharomyces, and Candida were positively correlated with butan-2-one-M. This study provides a theoretical basis for explaining the mechanisms of MTD flavor formation and screening functional microorganisms to improve the quality of MTD.

Dynamic changes in microbial communities and volatile compounds in kombucha fermentation using Flos sophorae and Elm fruits, compared to black and green tea

The dynamic changes in physicochemical properties, microbial communities, and volatile compounds in kombucha made from Flos sophorae (FLSK) and Elm fruit (EFK) were compared to those of black tea (BTK) and green tea (GTK) over a 12-day fermentation period. The results revealed that overall flavonoid and polyphenol content, as well as antioxidant activity, increased initially and then decreased, accompanied by a steady reduction in pH within the fermentation broths investigated. Notably, the GTK exhibited stronger antioxidant activity than the other fermentation broths. Furthermore, 16S rRNA gene sequencing revealed that Komagataeibacter rhaeticus, Komagataeibacter saccharivorans, and Acidovorax wautersii were the dominating microbial species in the fermentation broths under this study. Komagataeibacter rhaeticus initially reduced and then increased throughout the FLSK fermentation, whereas Komagataeibacter saccharivorans increased from day 0 to day 6, and remain stable by day 12 during the EFK fermentation. Comparative analysis revealed that Komagataeibacter rhaeticus was more abundant in the FLSK and GTK than in the EFK and BTK, whereas Komagataeibacter saccharivorans showed a higher abundance in the EFK relative to the other fermentation broths. Gas chromatography-mass spectrometry identified acetic acid, linalool, ethanol, and ethyl acetate as the major volatile chemicals that rose significantly in fermentation mixtures of the examined substrates. The FLSK had a much higher linalool concentration than the other fermentation broths, although the EFK and GTK had higher ethanol content. Correlation study found that Komagataeibacter rhaeticus was negatively related with alcohol compounds, but Komagataeibacter saccharivorans was positively associated with a diverse spectrum of acids, alcohols, and esters. The study found changes in bioactive chemicals as well as interactions between bacterial populations and volatile compounds throughout fermentation in the substrates investigated.

Effect of temperature on the quality and microbial community during Daocai fermentation

Daocai is a traditional salted pickle in the southeastern region of Guizhou with a unique aroma, color, and taste. The quality of Daocai is greatly influenced by the fermentation temperature. In this study, high-throughput sequencing and headspace-gas chromatography-ion mobility spectrometry were used to investigate the changes in microbial community succession and volatile flavor compounds during Daocai fermentation under temperature-controlled (D group) and non-temperature-controlled (C group).We found that the predominant genera in the C group samples were Latilactobacillus(40.57 %), Leuconostoc(21.25 %), Cystofilobasidium(22.12 %), Vishniacozyma(23.89 %), and Leucosporidium(24.95 %), whereas Weissella(29.39 %), Lactiplantibacillus(45.61 %), Mucor(68.26 %), and Saccharomyces(23.94 %) were the predominant genera in the D group. A total of 92 VFCs were detected in Daocai samples, including 5 isothiocyanates, 16 esters, 14 alcohols, 24 aldehydes, 17 ketones, 3 acids, 2 pyrazines, 1 pyridines, 1 thiazoles, 3 furans, 4 alkenes, and 2 nitriles. Further analysis revealed Latilactobacillus, Leuconostoc, Lactococcus, Cystofilobasidium, Leucosporidium, Holtermanniella, and Dioszegia as key bacteria involved in flavor formation. They are closely related to the formation of flavors such as aldehydes, furans, pyridines, and alkenes. This study contributes to our understanding of the relationship between bacterial communities and the flavor formation during Daocai fermentation.

Interaction and dynamic changes of microbial communities and volatile flavor compounds during the fermentation process of coffee flower rice wine.

To develop a unique flavor of rice wine, coffee flowers (by-products of the coffee industry) were added because of their biologically active compounds that are conducive to health, and the fermentation parameters were optimized. In addition, the dynamic changes of microbial communities and volatile flavor compounds (VFCs) during the different fermentation stages were investigated. After the optimization of the fermentation parameters, a novel product, i.e., the coffee flower rice wine (CFRW), was obtained with a bright yellow transparent, fragrant, and harmonious aroma and mellow and refreshing taste by sensory evaluation, when 4.62% of the coffee flowers and 1.93% koji were added and fermented at 24.10°C for 3.88 days. The results showed that Lactococcus was the dominant bacteria, accounting for 87.0-95.7%, while Rhizopus and Cladosporium were the main fungi, accounting for 68.2% and 11.3% on average, respectively, in the fermentation process of the CFRW. Meanwhile, twenty-three VFCs were detected in the CFRW, which included three alcohols, six terpenes, ten esters, three aromatics, and one furan. The correlation analysis revealed that there were 16 significant positive correlations and 23 significant negative correlations between the bacterium and VFCs (|ρ| > 0.6, p < 0.05), while there were 12 significant positive correlations and one significant negative correlation between the fungi and VFCs (|ρ| > 0.6, p < 0.05). Furthermore, five VFCs, including linalool, geraniol, ethyl acetate, 1-hexanol, and 3-methyl-1-butanol, contributed vital flavors to the CFRW, and they were all significantly negatively correlated with the changes of Massilia and Acinetobacter (|ρ| > 0.6, p < 0.05). Moreover a significant positive correlation was found between the relative abundance of Lactococcus and the contents of 3-methyl-1-butanol and ethyl acetate (|ρ| > 0.6, p < 0.05). Therefore, this study provides a valuable theoretical basis for further improving the quality and production technology of CFRW.

Effects of sorghum varieties on microbial communities and volatile compounds in the fermentation of light-flavor Baijiu.

Light-flavor Baijiu (LFB) fermentation is a representative spontaneous mixed-culture solid-state fermentation process in which sorghum is used as the raw material. Raw materials and microorganisms are crucial to the flavor formation and quality of LFB. However, the microbial and physicochemical dynamics of different sorghum varieties during LFB fermentation, as well as their impact on flavor compounds are still largely unknown. Herein, PacBio single-molecule real-time (SMRT) sequencing and headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) were applied to investigate microbial community succession and volatile flavor formation in glutinous/non-glutinous sorghum-based fermented grains during LFB fermentation. Fermented grains made of glutinous sorghum Liangnuo No. 1 (GLN) had higher bacterial α-diversity and lower fungal α-diversity than those with fermented grains prepared with non-glutinous red sorghum (NRS) (p < 0.05). The dominant microbial species were Saccharomyces cerevisiae, Acetobacter pasteurinus, and Lactobacillus helveticus, the latter two of which were the predominant bacteria observed at the end of fermentation in GLN and NRS, respectively. Moisture content and reducing sugar had a more significant impact on the microorganisms in GLN, while amino acid nitrogen, total free amino acids, and residual starch were the main driving factors driving the microbial community in NRS. The correlation network and discriminant analysis indicated that a relatively high content of 4-vinylguaiacol showed a significant positive association with significant differential microbial species in GLN. These results provided valuable insights for improving the quality of LFB.

Dynamics and correlation between volatile compounds and microbial community in chestnut rice wine fermentation

SummaryChestnut rice wine, also called banli mijiu (BLMJ), uses Chinese chestnut (Castanea mollissima Blume) in the fermentation of traditional glutinous rice wine. This study characterised the microbial communities and volatile compounds in BLMJ and explored their correlations. Headspace solid‐phase microextraction‐gas chromatography–mass spectrometry (HS‐SPME‐GC–MS) revealed that the major volatile compounds during BLMJ fermentation include eighteen important volatile compounds (OAV &gt; 1). High‐throughput sequencing (HTS) demonstrated that the abundance and diversity of bacteria were significantly greater than those of fungi during the fermentation process. Among them, Kropensteria and Saccharomyces were the most abundant bacteria and fungi at the genus level during the fermentation of BLMJ. Spearman's correlation analysis revealed that eighteen important volatile compounds were significantly positively correlated with seven microbial genera (|r| &gt; 0.9, P &lt; 0.01), including six bacterial genera (Rhodococcus, Lactococcus, Pseudomonas, Janthinobacterium, Unclassified_f_Bacillaceae and Burkholderia‐Caballeronia‐Paraburkholderia) and one fungal genus (Saccharomyces). Therefore, these bacterias and fungi may be core functional microorganisms during BLMJ fermentation. The findings may provide important reference for mediating the microbial community during fermentation to improve the flavour of BLMJ.

The potential correlation between the succession of microflora and volatile flavor compounds during the production of Zhenba bacon

Microbial composition plays an important role in the quality and flavor of bacon. The aims of this study were to detect bacterial community succession using high-throughput sequencing (HTS) and volatile flavor compound changes using gas chromatography-ion mobility spectrometry (GC-IMS) during the production of Zhenba bacon. The results showed that a total of 70 volatile compounds were detected. Among them, ketones, hydrocarbons, aldehydes, esters and alcohols were the main substances in the curing and smoking stages. In addition, the fungal abundance was greater than the bacterial abundance, and there was obvious succession of the microbial community with changes in fermentation time and processing technology. The main functional bacterial genera in the curing and smoking stages were Staphylococcus, Psychrobacter and Latilactobacillus, and the main fungal genera were Fusarium and Debaryomyces. Through correlation analysis, we found that pyrrole, 2-pentanol, methyl isobutyl ketone (MIBK) and ethyl acetate (EA) were significantly correlated with Staphylococcus, Psychrobacter, Pseudomonas and Myroides (p < 0.01), and it is speculated that they contribute significantly to flavor formation. The results of this study are helpful for understanding the microbial dynamics and characteristic volatile flavor compounds in Zhenba bacon, and provide new insights into the relationship between microorganisms and flavor through potential correlations.

Lacto-fermented garlic handcrafted in the Lower Silesia Region (Poland): Microbial diversity, morpho-textural traits, and volatile compounds

The aim of the present study was to provide a first characterization of lacto-fermented garlic manufactured by local small-scale artisanal producers in the Lower Silesia Region (Poland). The lacto-fermented garlic samples showed high nutritional features in terms of antioxidant activity. A total of 86 compounds, belonging to various chemical classes, were identified by headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC/MS). Most of these compounds belonged to six main classes, being sulfur compounds, esters and acetates, oxygenated monoterpenes, monoterpene hydrocarbons, and alcohols. Aldehydes, acids, ketones, furans, and phenols were also identified. In the analyzed samples, counts up to 8 log cfu g−1 were observed for lactic acid bacteria. Metataxonomic analysis revealed the presence of Levilactobacillus, Lactiplantibacillus, Latilactobacillus, Secundilactobacillus, Weissella, Leuconostoc, Lactococcus, Pediococcus, and Lacticaseibacillus among the major taxa. These results were confirmed by the isolation and characterization of viable lactic acid bacteria. Indeed, the presence of the closest relatives to Lacticaseibacillus casei group, Pediococcus parvulus, Levilactobacillus brevis, Levilactobacillus parabrevis, and Lactiplantibacillus plantarum group was observed. A good acidification performance in salty garlic-based medium was observed for all the isolates that, between 8 and 15 days of fermentation, reached pH values comprised between 4 and 3.5, depending on the tested species. Of note, 15 out of the 37 lactic acid bacteria isolates (Levilactobacillus parabrevis, Pediococcus parvulus, Lactiplantibacillus plantarum group, and Lacticaseibacillus casei group) showed the presence of the hdcA gene of Gram-positive bacteria encoding for histidine decarboxylase. Furthermore, for 8 out of the 37 isolates the in-vitro exopolysaccharides production was observed. No isolate showed inhibitory activity against the three Listeria innocua strains used as surrogate for Listeria monocytogenes.

Changes in the Quality and Microbial Communities of Precooked Seasoned Crayfish Tail Treated with Microwave and Biological Preservatives during Room Temperature Storage.

The qualities of precooked foods can be significantly changed by the microorganisms produced during room temperature storage. This work assessed the effects of different antibacterial treatments (CK, without any treatment; microwave treatment, MS; microwave treatment and biological preservatives, MSBP) on the physicochemical properties and microbial communities of precooked crayfish tails during room temperature storage. Only the combination of microwave sterilization and biological preservatives significantly inhibited spoilage, as evidenced by the total viable count (4.15 log CFU/g) after 3 days of room temperature storage, which satisfied the transit time of most logistics companies in China. Changes in pH and TVB-N were also significantly inhibited in the MSBP group compared with those in the CK and MS groups. More than 30 new volatile compounds were produced in the CK groups during room temperature storage. However, in the MSBP groups, the volatile compounds were almost unchanged. The correlations between the microbial composition and volatile compounds suggested that specific bacterial species with metabolic activities related to amino acid, energy, cofactor, and vitamin metabolism, as well as xenobiotics biodegradation and metabolism, were responsible for the changes in volatile compounds. These bacteria included Psychrobacter, Arthrobacter, Facklamia, Leucobacter, Corynebacterium, Erysipelothrix, Devosia, Dietzia, and Acidovorax. Overall, our findings provide a foundation for the development of strategies to inhibit spoilage in precooked crayfish tails stored at room temperature.

Correlation between microbial communities and volatile flavor compounds in the fermentation of Semen Sojae Praeparatum

SSP (Sojae Semen Praeparatum, SSP), a traditional medicinal and edible product, undergoes natural fermentation resulting in a unique flavor. However, the complexity of the natural fermentation system results in inconsistent quality. This study utilized E-nose, headspace solid-phase microextraction combined with full two-dimensional gas chromatography-mass spectrometry, and high-throughput sequencing techniques to reveal the correlation between key volatile flavor compounds and dominant microbial communities during SSP fermentation. The results showed that total organic acids increased from 50.61 mg/g to 72.29 mg/g during SSP fermentation, and levels of umami and sweet amino acids significantly increased. Alcohols, esters, and acids were the main flavor compounds during SSP fermentation, with 52 being identified as key volatile flavor compounds. In the microbial community, bacterial communities dominated by Proteobacteria, Cyanobacteria, and Firmicutes exhibited dynamic solid changes, while fungal communities dominated by Ascomycota, Basidiomycota, unclassified_Fungi, and Mortierellomycota showed relatively stable abundance. Spearman correlation analysis showed that 9 dominant microbial genera were significantly correlated with 27 key volatile flavor compounds, among which Cladosporium, Leuconostoc, Weissella, and Lactiplantibacillus may be the core functional microbial community for SSP characteristic flavors. This study provided theoretical references for the targeted control of SSP quality and the screening of starter fermentation cultures.

Unravelling the correlations among the microbial community, physicochemical properties, and volatile compounds of traditional mung bean sour liquid

Sour liquid noodles are a characteristic traditional food in Luoyang, China. Mung bean sour liquid (MBSL) is fermented from mung beans and used to cook noodles (instead of using water). However, the microbial community, volatile compounds, and physicochemical properties of MBSL are still unclear. Here, a comprehensive study was conducted using a combination of Illumina HiSeq sequencing, gas chromatography‒mass spectrometry detection, and physicochemical analysis methods. Eight phyla and 59 genera of bacteria were identified in MBSL, of which 4 genera were dominant, namely, Lactobacillus, Lactococcus, Leuconostoc, and Lelliottia. Six phyla and 123 genera of fungi were detected, with 11 genera being dominant. The protein content, total acid content, and pH mainly influenced the microbial community. Myroides, Aeromonas, Flavobacterium, and Lactobacillus, etc. May play important roles in balancing MBSL ecosystems. There were 40 volatile compounds in MBSL, with 1-hexanol, eugenol, acetic acid, and hexanoic acid being considered key volatile compounds. Lactobacillus, Algoriella, Lelliottia, and Leuconostoc were significantly correlated with the volatile compounds found in MBSL. The complex correlation between microbial communities, volatile compounds, and physicochemical properties may be elucidated through these findings. Controlling environmental factors and increasing the number of selected microbial cultures may improve the quality of MBSL.

Functional benefits of probiotic fermented dairy drink elaborated with sheep milk processed by ohmic heating

This study examined the effects of ohmic heating pasteurization on probiotic fermented sheep milk compared to conventional heating by analyzing microbial viability, volatile compounds, riboflavin content, and bioactive peptides in the resulting dairy product. Four batches of milk were processed using conventional heating (CH) and three different ohmic heating (OH). Microbiological analysis demonstrated the safety of OH-processed milk. Probiotic viability remained consistent during fermentation and storage, and the simultaneous inoculation of bacteria reduced fermentation time, indicating cooperation interplays. OH-processed probiotic fermented sheep milk showed a substantial increase in antioxidant, antidiabetic, antihypertensive activities, and riboflavin content. Moreover, the flavor profile was characterized by specific volatile compounds. Multiple-factor analysis was performed to identify relationships between samples and various parameters, offering insights into the impact of processing methods. In conclusion, OH enhanced the health-promoting and flavor-related compounds of probiotic fermented sheep milk, suggesting its application to produce functional dairy products.

Analyzing microbial community and volatile compound profiles in the fermentation of cigar tobacco leaves

Variations in industrial fermentation techniques have a significant impact on the fermentation of cigar tobacco leaves (CTLs), consequently influencing the aromatic attributes of the resulting cigars. The entire fermentation process of CTLs can be categorized into three distinct phases: phase 1 (CTLs prior to moisture regain), phase 2 (CTLs post-moisture regain and pile fermentation), and phase 3 (CTLs after fermentation and drying). These phases were determined based on the dynamic changes in microbial community diversity. During phase 2, there was a rapid increase in moisture and total acid content, which facilitated the proliferation of Aerococcus, a bacterial genus capable of utilizing reducing sugars, malic acid, and citric acid present in tobacco leaves. In contrast, fungal microorganisms exhibited a relatively stable response to changes in moisture and total acid, with Aspergillus, Alternaria, and Cladosporium being the dominant fungal groups throughout the fermentation stages. Bacterial genera were found to be more closely associated with variations in volatile compounds during fermentation compared to fungal microorganisms. This association ultimately resulted in higher levels of aroma components in CTLs, thereby improving the overall quality of the cigars. These findings reinforce the significance of industrial fermentation in shaping CTL quality and provide valuable insights for future efforts in the artificial regulation of secondary fermentation in CTLs.Key points• Industrial fermentation processes impact CTLs microbial communities.• Moisture and total acid content influence microbial community succession in fermentation.• Bacterial microorganisms strongly influence CTLs’ aldehyde and ketone flavors over fungi.

Correlation study on microbial communities and volatile flavor compounds in cigar tobacco leaves of diverse origins

To elucidate the significant influence of microorganisms on geographically dependent flavor formation by analyzing microbial communities and volatile flavor compounds (VFCs) in cigar tobacco leaves (CTLs) obtained from China, Dominica, and Indonesia. Microbiome analysis revealed that the predominant bacteria in CTLs were Staphylococcus, Aerococcus, Pseudomonas, and Lactobacillus, while the predominant fungi were Aspergillus, Wallemia, and Sampaiozyma. The microbial communities of CTLs from different origins differed to some extent, and the diversity and abundance of bacteria were greater than fungi. Metabolomic analysis revealed that 64 VFCs were identified, mainly ketones, of which 23 VFCs could be utilized to identify the geographical origins of CTLs. Sixteen VFCs with OAV greater than 1, including cedrol, phenylacetaldehyde, damascone, beta-damascone, and beta-ionone, play important roles in shaping the flavor profile of CTLs from different origins. Combined with the correlation analysis, bacterial microorganisms were more closely related to key VFCs and favored a positive correlation. Bacillus, Vibrio, and Sphingomonas were the main flavor-related bacteria. The study demonstrated that the predominant microorganisms were essential for the formation of key flavor qualities in CTLs, which provided a theoretical reference for flavor control of CTLs by microbial technology.Key points• It is the high OAV VFCs that determine the flavor profile of CTLs.• The methylerythritol phosphate (MEP) pathway and the carotenoid synthesis pathway are key metabolic pathways for the formation of VFCs in CTLs.• Microbial interactions influence tobacco flavor, with bacterial microorganisms contributing more to the flavor formation of CTLs.Graphical

Temporal Profile of the Microbial Community and Volatile Compounds in the Third-Round Fermentation of Sauce-Flavor baijiu in the Beijing Region.

Sauce-flavor baijiu produced in the Beijing and Guizhou regions has regional characteristic flavors, but the differences in flavor compounds and reasons for their formation remain unclear. The sauce-flavor baijiu brewing process involves several rounds of fermentation. In this study, we investigated the temporal distribution of microbial communities and flavor substances during the third round of sauce-flavor baijiu fermentation in the Beijing region, and we then compared and analyzed the differences of flavor substances and microorganisms in the fermented grains of sauce-flavor baijiu in the Beijing and Guizhou regions. It was found that 10 bacterial genera and 10 fungal genera were dominant in the fermented grains. The acidity of the fermented grains had a significant driving effect on the microbial community succession. A total of 81 volatile compounds were identified and quantified in the fermented grains, of which esters and alcohols were relatively abundant. The differences in 30 microbial community compositions and their resulting differences in terms of the fermentation parameters of fermented grains are responsible for the differences in the profiles of flavor compounds between sauce-flavor baijiu produced in the Beijing and Guizhou regions.

Effect of indigenous Saccharomyces cerevisiae strains on microbial community successions and volatile compounds changes during Longyan wine fermentation

In Longyan grape, as a unique white wine variety in China, the connection between starters and wine flavor is poorly understood. Thus, this study compared the effects of commercial yeast VL2 and three selected native Saccharomyces cerevisiae strains on the microbial community and volatile compounds during alcohol fermentation of Longyan wine. Results showed that the indigenous yeast strain FMS can initiate fermentation faster than other strains. A total of 60 aromatic compounds were identified in all fermentation samples, and the concentration of volatile compounds in wines inoculated with FMS (9619.61 ± 500.18 μg/L) was significantly higher than in VL2 wines (8358.91 ± 131.48 μg/L). Moreover, the microbial diversity differed among the four strains, with the FMS fermentation samples having the highest microbial genus of 470. The core microorganisms of VL2 (13), JCT (15), FMS (18), and FML (12) wines were identified using OPLS analysis and Spearman's correlation analysis, respectively. Among them, Lactobacillus, Paenibacillus, and Pichia were the unique microorganisms in FMS wines, which performed a crucial part in the synthesis of aromatic compounds such as hexyl acetate, ethyl butanoate, ethyl octanoate, and ethyl 9-decenoate. Therefore, FMS wines has effectively improved the quality of the wines and diversified the organoleptic quality of Longyan wines from Huaizhuo Basin. This study provided useful references for understanding the role of brewing yeast in the formation of flavor compounds during the fermentation process of Longyan dry white wine, as well as the application of indigenous brewing yeast in the wine industry.

Comparison of the Correlations of Microbial Community and Volatile Compounds between Pit-Mud and Fermented Grains of Compound-Flavor Baijiu.

The microbial composition and volatile components of fermented grains (FG) and pit mud (PM) are crucial for the quality and flavor of compound-flavor baijiu (CFB). The physicochemical indices, culturable microorganisms, microbial communities, and volatile components of FG and PM were analyzed and correlated in our research. Considering FG and PM, amplicon sequencing was used to analyze the microbial community and the volatile components were detected by headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME). For FG, redundancy analysis and correlation perfume Circos were used to clarify the correlations between the dominant microbial community and volatile components. The results showed that Aspergillus, Pichia, and Rhizopus were the main fungal microflora in FG and PM, whereas Lactobacillus and Bacillus were the dominant bacteria in FG, and Methanosarcina and Clostridium sensu stricto 12 were the dominant bacteria in the PM. The microbial community and volatile compounds in the CB sampled from the bottom layers of the FG were greatly affected by those in the PM. There were 32 common volatile components in CB and PM. For FG, most of the volatile components were highly correlated with Lactobacillus, Bacillus, Aspergillus, Pichia, and Monascus, which includes alcohols, acids and esters. This study reveals correlations between microbial composition, volatile components, and the interplay of FG and PM, which are conducive to optimizing the fermentation process and improving the quality of CFB base.

Microbial Volatile Compounds: Prospects for Fungal Phytopathogens Management, Mechanisms and Challenges

Microbial Volatile Compounds: Prospects for Fungal Phytopathogens Management, Mechanisms and Challenges

Microbial populations, sensory, and volatile compounds profiling of local cooked rice

Abstract Objectives This study is designed to investigate the microbial populations, sensory, and volatile compounds profiling of locally cooked rice stored at room temperature (30 °C) on days 0, 1, 2, and 3 (D0, D1, D2, and D3) for the determination of specific spoilage organisms (SSOs). Materials and Methods Microbiological, physicochemical, sensory evaluation, and volatile organic compounds (VOCs) analyses were conducted for samples of cooked rice stored at room temperature on days 0, 1, 2, and 3. SSO of cooked rice was then identified by linking present organisms with the changes occurring throughout the storage period. Results Microbiological analysis revealed the presence of spore-forming bacteria, yeast, and moulds, which survived the cooking process. While total viable count exceeded the microbiological limit at 6.90 log CFU/g on D3, panellists deemed cooked rice unacceptable for consumption on D2 at a total sensory score of 11.00, which indicates that D2 was the day cooked rice spoiled. Through culture-dependent and culture-independent methods, Bacillus cereus was identified as the sole bacteria observed throughout the storage period, confirming that the bacteria were SSOs. The VOC analysis proposed several metabolites, 3-eicosene, 1-heptadecene, hexacosane, phenol, 4,4ʹ-(1-methylethylidene)bis-, n-nonadecanol-1, and cyclohexanone, as potential spoilage markers of cooked rice. Conclusions B. cereus is confirmed to be the SSO of cooked rice, in which spoilage occured after 48 h of storage at room temperature. The organoleptic rejection in cooked rice was shown to be linked to the production of various compounds by B. cereus which could be proposed as potential spoilage markers for cooked rice.

Dynamic Changes in Microbial Communities, Physicochemical Properties, and Flavor of Kombucha Made from Fu-Brick Tea.

In this study, Fu-brick tea (FBT) was used for kombucha preparation. The succession of microbial community structures, changes in physicochemical properties, and the volatiles were investigated during the kombucha fermentation. The sequencing analysis showed that Komagataeibacter was the most predominant bacterium. Aspergillus and Zygosaccharomyces were the dominant fungi before fermentation whereas Zygosaccharomyces and Derkella were the dominant fungi after 3 days of fermentation. The physicochemical analysis revealed that acetic acid, glucuronic acid, and polyphenols increased by 10.22 g/L, 0.08 g/L, and 177.40 mg/L, respectively, by the end of fermentation. The GC-MS analysis showed that a total of 49 volatile compounds were detected during the fermentation. Moreover, there were great differences in volatile components among the kombucha samples with different fermentation times. Furthermore, the relevance among microbial community and volatile compounds was evaluated through correlation network analysis. The results suggested that Komagataeibacter, Aspergillus, Zygosaccharomyces, and Dekkera were closely related to the main volatile compounds of FBT kombucha. The results in this study may provide deep understanding for constructing the microbiota and improving the quality of FBT kombucha.