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•LABs (Weissella, Lactobacillus, and Pediococcus) were dominant bacteria around day 2.•Thermotolerant/thermophilic taxa exhibited the highest proportion after day 6.•A metabolic ...network of core microbes involved in flavor development was constructed.•Potential populations responsible for the production of lytic enzymes were revealed.•Lactic acid and bio-heat produced by microbes could promote the microbiota shift.
As a widely used Asian starter culture, the quality of daqu can significantly affect the organoleptic characteristics of the final products, yet the microbial metabolic network involved in flavor development remains unclear. This study aims to investigate that network based on the dynamics of physicochemical properties, microbial community, and volatile compounds in medium-temperature daqu (MT-daqu) during spontaneous fermentation. Analyses using the metagenomic data set facilitated the gene repertoire overview of this ecosystem, indicating that Lactobacillales (mainly Weissella, Lactobacillus, and Pediococcus), Mucorales (mainly Lichtheimia), and Eurotiales (mainly Aspergillus, Rasamsonia and Byssochlamys) were the potential predominant populations successively responsible for the production of lytic enzymes and flavor precursors/compounds in MT-daqu. Flavor-relevant pathways were found to exist in multiple species, but only bacteria showed the potential to participate in butane-2,3-diol (e.g. Weissella, Lactobacillus, and Staphylococcus) and butanoate (Thermoactinomyces) metabolism, and only fungi were potentially involved in biosynthesis of guaiacol (Byssochlamys) and 4-vinylguaiacol (Aspergillus). Furthermore, a combined analysis revealed that the acidic thermal environment present in early phases was mainly due to the catabolic activities of Lactobacillales and Lichtheimia, which could contribute to the effective self-domestication of microbiota. The study helps elucidate the different metabolic roles of microorganisms and disclose the formation mechanism of daqu’s partial functions, namely providing various aromatic substances/precursors and enzymes.
Fermented foods, with a history as long as the human civilization, form an indispensable constituent in our daily life. However, most fermented foods are produced by spontaneous fermentation, and the ...fermentation processes are still uncontrolled. To ensure consistent food quality, it is of paramount importance to understand and control the spontaneous food fermentations.
In spontaneous food fermentations, metabolic activity of a succession of complex microbiota results in desired flavour that is the key criterion to decide consumers’ preference. Therefore, flavour compound formation by microbial metabolism can be used as the control target in spontaneous food fermentations. However, relatively little is known about the complexity of the microbiota associated with the flavour compound formation. Therefore, in this review by using Chinese liquor as a model system, we present key biotechnological aspects of the microbiota crucial for flavour of fermented foods, including the driving forces for the microbiota succession, flavour compound formation, and the regulation of flavour compound formation.
Core microbiota, associated with flavour compound formation, can be identified and eventually used to construct a synthetic (i.e. designed) microbiota. Meanwhile, key environmental factors, affecting the core microbiota, can also be identified and controlled to regulate the synthetic microbiota. Furthermore, modelling can be used to predict, optimize and control the flavour compound formation by the synthetic microbiota, so that such spontaneous food fermentations can become controllable, with the ultimate goal to monitor, control, and improve the quality, productivity and safety of fermented foods.
•Flavour compound can be controlled via regulating microbiota in food fermentation.•Core microbiota and key environmental factors should be identified in fermentation.•Synthetic microbiota can provide a tractable and controllable fermentation.•Environmental parameters are yet another factor to affect the microbiota.•Modelling can be used to predict and optimize the flavour compound formation.
Chinese liquor, a very popular fermented alcoholic beverage with thousands of years’ history in China, though its flavour formation and microbial process have only been partly explored, is facing the ...industrial challenge of modernisation and standardisation for food quality and safety as well as sustainability. Meanwhile, the hidden knowledge behind the complicated and somehow empirical solid-state fermentation process of Chinese liquor can enrich the food sector to improve our quality of life, and benefit other industrial sectors in the modern biomass-based technology, economy and society.
This review reveals the traditional fermentation process and characteristics of Chinese liquor, summarises the current study progress of flavour chemistry and responsible microbial process, and addresses future improvement and research needs. We provide here a detailed, systematic and critical review on Chinese liquor to improve the current industrial practice and serve the modern society with yet incompletely explored but useful principles.
The hidden knowledge behind the traditional Chinese liquor production is rich in useful principles including flavour chemistry, microbial growth, solid-state fermentation, enzyme production, biocatalysis, microbial community metabolism and process engineering. Studies in a more in-depth, systematic and practical way on this look-like empirical process to explore the scientific principles behind will definitely benefit the liquor industry in particular, and the (food) biotechnology sector in general.
•Traditional Chinese liquor fermentation faces industrial challenge of modernisation.•Traditional liquor fermentation is a treasure to explore for quality of life today.•Hidden knowledge is valuable to study and apply in food and biotechnology sectors.•Multidisciplinary approach will accomplish innovation and improvement.
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•Phospholipids were separated and identified in a biosurfactant extract from corn.•Phospholipids can be precipitated with acetone.•Acid hydrolysis plays an important role in the ...identification of lipopeptides.•Amino acids in lipopeptides were identified after hydrolysis with HCl.•Fatty acids in lipopeptides were hydrolyzed with HCl and extracted with ether.
This is the first work about the fractionation, separation and identification of different bioactive compounds contained in a multifunctional biosurfactant extract, obtained from corn steep water through a liquid–liquid extraction with chloroform. In this extract, phospholipids (21%) were precipitated with acetone and identified by electrospray ionization mass spectrometry (ESI-MS/CID), detecting a characteristic signal at 758 m/z that corresponds with phosphatidylethanolamine and phosphatidylcholine. In this extract, major biomarkers at 879 and 933 m/z and small signals between 1000 and 1500 m/z were also detected, corresponding with lipopeptides (25%) with different molecular weights. For determining the amino acids and fatty acids of these lipopeptides, the biosurfactant extract, obtained from corn steep water, was subjected to acid hydrolysis. Subsequent, the fatty acids contained in the hydrolysate were extracted with ether and analyzed by gas chromatography–mass spectrometry (CG-MS), discovering the presence of C16 and C18 fatty acids. Additionally, the hydrolyzed peptides, solubilized in the aqueous phase, were analized using ESI-MS/MS/CID, identifying glutamic acid/glutamine, aspartic acid/asparagine, glycine, alanine, arginine, proline and leucine/isoleucine. Free fatty acids (49.1%) were also quantified by titration with KOH. Remarkably, all the compounds identified in this multifunctional biosurfactant have high interest for obtaining more compatible formulations in different industries.
‘Marselan’ is a promising wine grapevine with unique qualities, studies on its introduction and characteristics have never stopped. However, little is known about the fermentation process of ...‘Marselan’ wine. In this study, we compared industrial-scale spontaneous (SMF) and inoculated (IMF) fermentation processes on the succession of microbial community and the change in volatile compounds and predicted their correlations. SMF could ferment ‘Marselan’ to dry red wine with alcohol content of 13.37% ± 0.76% (v/v) in 10 days and enhance the total concentration and odour activity values (OAVs) of volatile compounds. Ethyl caprylate, ethyl caprate, ethyl caproate and citronellol (OAVs > 1.0) were important volatile compounds in SMF and IMF wines. Compared with IMF, SMF was more outstanding in initial non-Saccharomyces diversity, including Hanseniaspora, Metschnikowia and Issatchenkia. In addition, Spearman's correlation (|ρ| > 0.7) and bidirectional orthogonal partial least squares (O2PLS, VIP > 1.0) analysis showed that some indigenous microorganisms in grape were closely related to the formation of volatile compounds, such as lactic acid bacteria, non-Saccharomyces and Saccharomyces cerevisiae. Overall, results showed that SMF could strengthen the flavour of ‘Marselan’ wine, and the possibility of consideration screening indigenous aroma-producing microorganisms as starter to improve the unique characteristics of ‘Marselan’ wine.
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•First report on microbial diversity succession during ‘Marselan’ wine fermentation.•Spontaneous fermentation resulted higher levels of volatile compounds.•Spontaneous fermentation was more outstanding in initial yeast diversity.•Non-Saccharomyces and lactic acid bacteria were closely related to volatile compounds.
Se estudió la evolución de la concentración de ácido fítico, fósforo libre y hierro soluble durante la fermentación de repollo blanco y repollo chino. En ambos casos, la máxima población de bacterias ...ácido lácticas se logró a los cinco días del proceso y luego disminuyó continuamente hasta el final. El pH inicial del repollo blanco y repollo chino fue de 6,1 y durante los primeros cinco días disminuyó a 3,7 y 4,3 respectivamente, luego permanecieron estables hasta los 30 días. En el repollo blanco, la concentración de ácido fítico disminuyó y el fósforo libre se incrementó durante los primeros cinco días, después no se detectaron cambios significativos. En el repollo chino, la degradación del ácido fítico se observó durante los primeros 15 días, mientras que el fósforo libre aumentó hasta el final del proceso. Ambos vegetales mostraron una concentración inicial de hierro comparable, luego, se observó un incremento hasta el final del proceso, siendo este fenómeno más notable en el repollo chino. Los resultados obtenidos sugieren que la degradación del ácido fítico producida durante la fermentación por la actividad de fitasas vegetales y bacterianas, no sólo origina la liberación de fósforo libre, sino que mejora la bioaccesibilidad del hierro.
Palabras claves. biodisponibilidad de nutrientes, fermentación espontánea, Brassica
Emphasize on natural wines has gained prominence in the wine industry. However, there is a lack of research on natural wines that are fermented relying solely on grape skin-resident microorganisms. ...The microbes in spontaneous and inoculated fermentation must were analyzed utilizing 16S ITS rRNA sequencing, metabolomics, and metagenomics. The upregulated primary metabolites involved in Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment pathways suggesting that the stress resistance of Saccharomyces was more robust and complex during spontaneous fermentation. Gene functional analysis indicated that Saccharomyces and non- Saccharomyces yeasts play crucial roles in carbohydrate metabolism, and their functions are complementary. The non- Saccharomyces yeasts contributed positively to the overall characteristics of the spontaneous wine. An analysis of the correlations between the dominant microorganisms and metabolites proved that more abundant strains participated in the fermentation of spontaneous wines and had a positive effect on the fermentation process of the wines.
•Using spontaneous fermentation without inoculated yeast or any auxiliaries.•Utilizing 16S ITS rDNA sequencing, metabolomics, and metagenomics techniques.•Starmerella and Hanseniaspora was involved in spontaneous fermentation.•More abundant strains positively affected the characteristics of spontaneous wine.
This study investigated the effects of spontaneous and Lactobacillus plantarum (LP) fermentation on structure glutinous proso millet starch (GPM) and physical properties. In order to explore starch ...changes by fermentation for quality regulation of fermented food glutinous proso millet and improve properties of modified GPM starch products. The molecular weight, amylopectin chain length distribution, morphological properties, short-range ordered structure, and crystal structure of GPM starch were analyzed. Results showed that compared with the non-fermented GPM starch, amylose content of spontaneous and LP-fermented GPM starch increased then decreased, with the latter decreasing faster. There were no changes in the Type A structures of spontaneous fermented, LP-fermented, and non-fermented GPM starch. After 24 h of LP fermentation, higher water swelling power, and lower GPM starch solubility were obtained compared to non-fermentation and spontaneous fermentation. The decrease in pasting properties and thermal properties while increasing GPM starch properties was shown after fermentation compared to non-fermentation experiments. Besides, LP fermentation showed faster changes of these properties than spontaneous fermentation. In conclusion, our findings showed that fermentation could improve GPM starch properties, benefiting fermented GPM products and as a modification method for GPM starch. Especially, LP fermentation was more effective than spontaneous fermentation.
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•The effect of SF and LPF on the structure and properties of GPM starch was studied.•SF and LPF influenced amylose content and amylopectin chain length distribution.•SF and LPF caused a decline in A-type of GPM starch relative crystallinity.•Fermentation is an effective method for modified GPM starch and LPF is better than SF.
Sichuan Paocai (SCP), a traditional fermentationed food, possesses unique flavours driven by various microbiota in fermentation ecosystems. However, the association between these microbiota and ...flavours is poorly understood. Here, we measured the structural dynamics of the microbial diversity and flavour compounds during SCP fermentation (0–7 days) using high-throughput sequencing and flavour analyses. Firstly, a total of 90 bacteria and 135 fungi were identified. The results showed that fermentation process was initiated by environmental microorganisms, such as Micrococcaceae, followed by a heterolactic fermentation phase dominated by Leuconostocaceae, and finally succeeded by homolactic fermentation led by Lactobacillaceae. Secondly, 6 organic acids, 12 amino acids and 86 volatile flavours were detected. The fermentation process was divided into 4 stages based on flavours: Day 0; Days 1–3; Days 4–6; and Day 7. Analysis of the correlation between microbiota and flavours indicated that bacteria contributed more to flavours formation than did fungi, and Lactobacillus, Leuconostoc, Achromobacter and Pediococcus were closely correlated with flavours. This study provides a systematic method for understanding the characteristics of fermented foods and useful guidelines for screening of strains that produce desirable flavours and functional substances.
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•Paocai fermentation was microbially 3-stage and aromatically 4-stage grouped.•Correlation between microbial diversity and corresponding flavour was revealed.•Microbial hallmark at different stage was captured by LEFSe.•Lactobacillus, Leuconostoc, Achromobacter, Pediococcus closely related to flavour.
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