Phase Of Fermentation Research Articles

Dynamics of fermentation quality, bacterial communities, and fermentation weight loss during fermentation of sweet sorghum silage

BackgroundSweet sorghum is used mainly as an energy crop and feed crop in arid and semiarid regions, and ensiling is a satisfactory method for preserving high-quality sweet sorghum. The aim of this study was to reveal the dynamics of the fermentation quality, bacterial communities, and fermentation weight loss (FWL) of sweet sorghum silage during fermentation.MethodsSweet sorghum was harvested at the first inflorescence spikelet stage and ensiled without (CK) or with lactic acid bacterial (LAB) additives (L). After ensiling, samples were collected on days 0, 1, 3, 5, 15, 40, and 100 to assess the fermentation quality, bacterial communities, and FWL.ResultsFor CK and L, on day 1, the pH was 5.77 and 5.57, respectively, and the lactic acid (LA) was 1.30 and 2.81 g/kg dry matter (DM), respectively. Compared with CK, L had a lower pH and higher LA from days 1 to 5 (P < 0.05), a lower FWL from days 5 to 100 (P < 0.05), and a greater abundance of Lactiplantibacillus from days 1 to 15 (P < 0.05). The main bacterial genera were Leuconostoc and Weissella in CK and Lactiplantibacillus, Leuconostoc, and Weissella in L on day 1; Lactiplantibacillus in all silages from days 3 to 40; and Lactiplantibacillus and Lentilactobacillus in all silages on day 100.ConclusionsSweet sorghum silage fermented relatively slowly during the first day. Moreover, inoculation with LAB accelerated fermentation and optimized bacterial communities during the initial fermentation phase. Inoculation with LAB also reduced the silage FWL, and the LAB succession relay occurred in the silage throughout the fermentation process.

Enhancing acid resistance of Escherichia coli based on directed morphology evolutionary of key transcription factor bolA

Succinic acid, as one of the important fermentation products, is commonly used as an acidulant, flavoring agent, and antimicrobial agent. However, the accumulation of organic acids in the later fermentation phase will restrict the production efficiency of strain. To address this issue, the directed evolution on the key transcription morphology factor bolA gene was performed to enhance acid resistance of Escherichia coli by ep-PCR library and CRISPR/Cas9. The best mutant strain 5-21-5 was screened from 4000 mutant colonies ep-PCR library, which showed higher cell survives in succinic acid stress. Its acid resistance ability was systematically illustrated from multiple aspects by transmission electron microscope (TEM), confocal laser scanning microscopy (CLSM), and three-dimensional excitation emission matrix (3D-EEM) analysis, respectively. Higher tyrosine and tryptophan protein level was beneficial to acid resistance, while cell tend to short rod shape. Subsequently, with the assistance of the CRISPR/Cas9 gene editing technology knocking the mutated sequences into the genome, the succinic acid yield of strain M-K10 reached 9.8 g/L, representing a 15.29% increase compared to the Escherichia coli MG1655 without gene editing.

Research on microbial diversity and nutritional flavor formation of Xianju wheat paste

AbstractBACKGROUNDXianju wheat paste, a traditional condiment in Hubei Province, China, possesses nutritional value and a distinctive taste profile. Nevertheless, there remains a dearth of comprehensive comprehension regarding the intricate interplay between the microbial population and its nutritional profile in Xianju wheat paste.RESULTSIt was determined that Xianju wheat paste harbors predominant microbial genera such as Bacillus, Staphylococcus and Aspergillus. The findings from high‐throughput sequencing analysis revealed the presence of 11 bacterial genera in Xianju wheat paste, with relative abundances exceeding 1%. These genera included Bacillus, Staphylococcus, Brevibacterium, Lactobacillus, Allorhizobium‐Neorhizobium‐Pararhizobium‐Rhizobium, Enterobacteriaceae, Pantoea, Brachybacterium, Klebsiella, Escherichia‐Shigella and Ochrobactrum. Furthermore, six fungal genera were identified with relative abundances greater than 1%, specifically Aspergillus, Zygosaccharomyces, Cutaneotrichosporon, Candida, Millerozyma and Rhizopus. The correlation analysis indicated a significant impact of the microbial community and nutritional flavor on the second phase of fermentation in Xianju wheat paste. The predominant bacterium Bacillus in Xianju wheat paste facilitated the production of free amino acids, whereas Staphylococcus exhibited a negative correlation with free amino acid levels. The quantity of volatile compounds in Xianju wheat paste progressively increased during fermentation, with the presence of typical aroma compounds 4‐vinyl‐2‐methoxyphenol significantly associated with Bacillus. This indicated Bacillus notably enhanced the production of aromatic substances. Furthermore, a strong correlation was observed between Staphylococcus and the 18 volatile organic compounds, highlighting their substantial contribution to these aroma compounds.CONCLUSIONThis research indicates that the presence of microbial communities significantly contributes to the development of the nutritional flavor profile in Xianju wheat paste. © 2024 Society of Chemical Industry.

Channel Engineering of a Glutamate Exporter.

Mechanosensitive channel MscCG2 is involved in glutamate excretion in most C. glutamicum strains. Improving the excretion efficiency of MscCG2 is beneficial to the production of glutamate. In this study, structure-based rational design was carried out to obtain an improved efflux ability of exporter MscCG2 and its mechanistic advance via two strategies: widening the channel entrance for smoother entry of glutamate and reducing the electronegativity at the entrance of the channels to minimize the rejection of negatively charged glutamate entry. The designed variants were found to enhance glutamate excretion by 2 to 3.3-fold in the early phase and 1.1-fold to 1.5-fold in the late phase of fermentation. The enhanced glutamate excretion was further confirmed by using glutamate toxic analog 4-fluoroglutamate (4-FG) and Glu-Glu peptide uptake and glutamate export assay. Molecular dynamic (MD) simulations revealed that the amino acid substitutions indeed enlarged the channel entrance and reduced the repulsion of glutamate when entering the channel. The finding of this study is important for understanding the underlying structure-function relationship and the mechanism of glutamate secretion to improve glutamate efflux efficiency of glutamate exporter.

Online Identification of Beer Fermentation Phases

Online Identification of Beer Fermentation Phases

Newly identified small vulcanian eruptions during the caldera-forming stage of Towada Volcano, Northeast Japan

Understanding the detailed eruptive history and conditions during the buildup to catastrophic caldera-forming eruptions is essential for understanding the evolution of caldera volcanoes and predicting eruptive hazards. Towada Volcano is an active caldera volcano in the northern part of the Northeast Japan Arc. At least two catastrophic caldera-forming eruptions (eruptive episodes N and L) occurred during its caldera-forming stage (61–15.7 ka). A detailed geological survey identified three small vulcanian tephra layers that were erupted during the caldera-forming stage. The tephra layers are blue–gray ash fall deposits that consist mainly of fresh blocky dacite–rhyolite fragments. In ascending order, these deposits are assigned to eruptive episodes O′, N′, and M′. Each eruption had a volume of <0.11 km3, which is much smaller than that of other eruptions during the caldera-forming stage. The eruptive ages of episodes O′, N′, and M′ are estimated to be ca. 40, 23.1, and 17.2 ka, respectively, based on new 14C ages and paleosol thicknesses data. At least three cycles of a medium- to large-scale (3–20 km3) explosive eruption, preceded by a small vulcanian eruption (<0.11 km3), occurred during the latter half of the caldera-forming stage. The small vulcanian eruptions (episodes O′, N′, and M′) occurred after relatively long periods of quiescence (4000–14,000 years) and were followed by medium- to large-scale explosive eruptions (episodes N, M, and L) 1500–4000 years later. This cyclic activity probably reflects changes in overpressure in the magma reservoir. As the overpressure increased, episodes O′, N′, and M′ probably occurred when the overpressure had not increased sufficiently to trigger a medium- to large-scale explosive eruption, and episodes N, M, and L occurred at higher overpressures. These cycles characterize the fermentation phase of Towada Volcano, and terminated with the formation of the Towada Caldera during episode L at 15.7 ka. The magma composition and eruption frequency changed abruptly after episode L, and a small stratovolcano was formed through intermittent eruptions of mafic magma. This change suggests that the caldera collapse during episode L changed the entire shallow magmatic system that existed during the fermentation phase, and the system shifted to a recovery (post-caldera) phase. Based on eruptive volumes and frequencies, the present Towada Volcano has not yet reached the conditions that existed during the late caldera-forming stage and is therefore unlikely to produce a catastrophic caldera-forming eruption in the near future.

Dynamics of gas and greenhouse gases production during fermentation of barley silage with lactic acid bacteria

Greenhouse gases (GHGs) are generated during fermentation in silages, especially in barley silage. However, little is known regarding the dynamics of GHG production in silages during fermentation. In the present study, GHG accumulation and reduction were assessed in barley silage. Barley was harvested at the milk stage and ensiled without (CK) or with two commercial lactic acid bacterial (LAB) additives (L1 or L2). Gas and GHG (CO2, N2O, and CH4) production, fermentation quality, fermentation weight loss (FWL), and bacterial communities were analyzed at d 0, 1, 3, 6, 15, 35, and 90 after ensiling. Gas and GHG production rapidly increased in CK during the first 3 days and in L1 and L2 during the first day and then decreased (P < 0.05), and these values were higher in CK than in L1 and L2 from d 1 to d 35 (P < 0.05), with the peak production of gas and GHG observed at d 6 in CK and at d 3 in L1 and L2. Gas and GHG production were positively correlated with the count of Coliforms and the abundances of Enterobacter, Klebsiella, and Atlantibacter from d 0 to 6 (P < 0.05) but were negatively correlated with the abundances of Lentilactobacillus, Lactiplantibacillus, and Lacticaseibacillus from d 1 to 35 (P < 0.05). L1 and L2 had increasing pH and acetic acid (AA) and decreasing lactic acid after d 15 (P < 0.05). Lentilactobacillus in L1 and L2 dominated the bacterial communities from d 35 to 90 and correlated positively with pH and AA, and negatively with LA from d 6 to 90 (P < 0.05). FWL had a positive correlation with gas and GHG from d 1 to 35 (P < 0.05). The ensiling fermentation process can be divided into gas accumulation and reduction phases. Inoculation with LAB reduced gas and GHG production. The activities of enterobacteria were the main contributors to gas and GHG accumulation. Lentilactobacillus activity mainly caused deterioration of fermentation quality during the late fermentation phase. The GHGs generated in silage contributed to the FWL during fermentation.Graphical

Estamaran date vinegar: chemical and microbial dynamics during fermentation.

Vinegar is a fermented food produced by alcoholic and then acetic acid microbial metabolism. Date palm fruit (Phoenix dactylifera L.) is a valuable source for the production of vinegar. Microbial identification has a major role in the improvement and bio-management of the fermentation process of vinegar. Estamaran and Kabkab two varieties of date palm fruit were selected to study the fermentation process. A culture-dependent approach was used to study bacterial dynamics. 16S rRNA gene was amplified by Polymerase Chain Reaction (PCR), also restriction enzyme analysis with HinfI and TaqI, and sequencing was done. Assessment of microbial flora of date palm fruit during fermentation showed that Fructobacillus tropaeoli, Bacillus sp., Leuconostoc mesenteroides, Leuconostoc pseudomesenteroides, and Weissella paramesenteroides existed in the first phase of fermentation. With fermentation progress, microbial diversity decreased so only one species remained. Komagataeibacter xylinus as an acid acetic producer was present in the third phase of fermentation. Based on chemical analysis, the concentration of reducing sugars decreased during fermentation. With decreasing pH, a simultaneous increase in acidity and total phenolic compounds occurred. The trend of changes during Estamaran fermentation was more severe and a vinegar with desirable properties was produced. Therefore, this date variety is recommended for the production of date vinegar.

A Study of Condensates Collected during the Fermentation of Grape Must

This article deals with the analysis of the condensates which are formed from fermentation gases during the fermentation of grape must. The experiment was divided into two parts. In the first part, the evolution of the individual volatiles was monitored throughout the whole fermentation process of the Riesling variety. In the second part, the condensates from three different grape varieties (Riesling, Merlot, Sauvignon blanc) were investigated and the total content of the selected volatile substances was measured at the end of the fermentation. Attention was focused on the measurements using a GC-MS (gas chromatography-mass spectrometry) for the volatile substances: isoamyl alcohol, isobutyl alcohol, 1-propanol, ethyl acetate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, acetaldehyde, acetic acid, and acetoin. In addition, changes in the alcohol content of the condensate, with respect to the fermentation phase, were analysed. From the results of part 1, the quantity of the substances under investigation produced during fermentation was determined. The highest concentration of flavour compounds was during the fourth and fifth days of fermentation. The most dominant substance was isoamyl alcohol with a concentration of 1267 mg−1.The results of part 2 led to a comparison of the overall profile of volatiles between the varieties. The results showed that the condensates have both a high content of volatile substances and of alcohol. It was also shown that the Sauvignon blanc variant had the highest number of volatile compounds in the representation. The Merlot and Riesling variants were very similar. This product has an exceptionally high potential for further use in the wine or food industry.

Physicochemical Characteristics, Microbiology, and Antioxidants of Goat Milk Kefir Supplemented with Clitoria ternatea L. Extract

Introduction: Kefir is manufactured by inoculating milk with kefir grains, followed by a one-day fermentation phase at room temperature. The addition of extracts of Clitoria ternatea L. to kefir is used as a source of antioxidants which are beneficial for health. Objective: This study aimed to determine the effect of adding extracts of C. ternatea L. on physicochemical characteristics, pH, titratable acidity, total lactic acid bacteria, antioxidant activity, and total phenol of goat milk kefir. Methods: This study used fresh goat milk, kefir granules, and C. ternatea L. extract. The administration of C. ternatea L .extract on goat milk kefir was A (0%), B (1.5%), C (3.0%), D (4.5%), and E (6.0%). Physicochemical characteristics (water, protein, fat, pH, titratable acidity), total lactic acid bacteria, antioxidant activity, and total phenol were observed in this study. Results: The statistical analysis results showed that adding C. ternatea L. extract to goat milk kefir significantly (P˂0.05) decreased water content, pH, increased protein, total titrated acid, and antioxidant activity, total phenol and not significant (P˃0.05) to total lactic acid bacteria. In this study, the pH value was 3.65-4.10, the total titrated acid was 0.78-1.23%, and the total lactic acid bacteria was 7.42-7.87×10⁸CFU/ml. Conclusion: The results showed that adding C. ternatea L. extract could increase antioxidant activity and total phenol while also containing lactic acid bacteria, giving it the potential to be a nutrition probiotic food. Adding 1.5% C. ternatea L. extract to kefir produced the best results, with a pH of 3.88, titratable acidity of 0.88%, and total lactic acid bacteria of 7.87 108CFU/ml.

In vitro digestion and colonic fermentation of phenolic compounds and their antioxidant potential in Australian beach-cast seaweeds

Beach-cast seaweed has recently garnered attention for its nutrient-rich composition, including proteins, carbohydrates, vitamins, minerals, and phytochemicals. This study focuses on the phenolic content and antioxidant potential of five Australian beach-cast seaweed species during in vitro digestion and colonic fermentation. The bioaccessibility of the selected phenolic compounds was estimated and short chain fatty acids (SCFAs) production was determined. Cystophora sp., showed a notable increase in phenolic content (23.1 mg GAE/g) and antioxidant capacity (0.42 mg CE/g) during the intestinal and gastric phases of in vitro digestion. Durvillaea sp. demonstrated a significant release of flavonoids (0.35 mg QE/g), while Phyllosphora comosa released high levels of tannins (0.72 mg CE/g) during the intestinal phase. During colonic fermentation, P. comosa released the highest levels of phenolic compounds (4.3 mg GAE/g) after 2 h, followed by an increase in flavonoids (0.15 mg QE/g), tannins (0.07 mg CE/g), and antioxidant activity (DPPH: 0.12 mg TE/g; FRAP: 0.61 mg TE/g) after 4 h. Moreover, P. comosa released a considerable amount of phenolic compounds during both in vitro digestion and colonic fermentation. All species consistently released phenolic compounds throughout the study. Phloroglucinol, gallic acid, and protocatechuic acid were identified as the most bioaccessible phenolic compounds in all five Australian beach-cast seaweeds in the in vitro digestion. Nevertheless, compound levels declined during the colonic fermentation phase due to decomposition and fermentation by gut microbiota. With regard to SCFAs, P. comosa displayed elevated levels of acetic (0.51 mmol/L) and propionic acid (0.36 mmol/L) at 2 h, while Durvillaea sp. showed increased butyric (0.42 mmol/L) and valeric (0.26 mmol/L) production acid after 8 h. These findings suggest that seaweed such as Cystophora sp., Durvillaea sp., and P. comosa are promising candidates for food fortification or nutraceutical applications, given their rich phenolic content and antioxidant properties that potentially offer gut health benefits.

Optimizing the winemaking process: NIR spectroscopy and e-nose analysis for the online monitoring of fermentation.

In the winemaking process, the rapid determination of specific quality parameters such as sugar content, pH, acidity, concentrations of phenolic compounds, anthocyanins and volatile organic compounds is crucial for high-quality wine production. Traditional analytical methods allow for precise quantification of these parameters but are time-consuming and expensive. This article explores the potential application of non-destructive analytical technique (NDAT) (near infra-red [NIR] and e-nose), as efficient alternatives for online monitoring of fermentation working on two different winemaking tanks and applying chemometrics to develop predictive models to correlate non-destructive and analytical data. NIR measurements have been used to build principal components regression models, showing good prediction capability for polyphenols, anthocyanins, glucose and fructose. Both offline and online e-nose applications demonstrate good capability of discriminating different fermentation phases, in agreement with aromatic profile changes observed via gas chromatography-mass spectrometry analysis. Moreover, correlation analysis reveals the potential of quartz microbalances, Taguchi Gas Sensors and H2 S sensors in predicting the concentration of compounds of great interest for winemaking (e.g. C6 alcohols, ketones, terpenes and ethyl esters) highlighting the robust connection between sensor data and specific chemical classes. This research aims to showcase the potential employment of NDAT for online monitoring the evolution of must composition during fermentation. The proposed methods could potentially fulfil a longstanding requirement of winemakers, enabling them to closely monitor fermentation allowing the timely making of important technical decisions aimed at achieving oenological objectives in wine production. © 2024 Society of Chemical Industry.

Influence of microbially fermented 2´-fucosyllactose on neuronal-like cell activity in an in vitro co-culture system.

2´-Fucosyllactose (2´-FL), the most abundant oligosaccharide in human milk, plays an important role in numerous biological functions, including improved learning. It is not clear, however, whether 2´-FL or a cleavage product could influence neuronal cell activity. Thus, we investigated the effects of 2´-FL, its monosaccharide fucose (Fuc), and microbial fermented 2´-FL and Fuc on the parameters of neuronal cell activity in an intestinal-neuronal transwell co-culture system in vitro. Native 13C-labeled 2´-FL and 13C-Fuc or their metabolites, fermented with Bifidobacterium (B.) longum ssp. infantis and B. breve, which were taken from the lag-, log- and stationary (stat-) growth phases of batch cultures, were applied to the apical compartment of the co-culture system with Caco-2 cells representing the intestinal layer and all-trans-retinoic acid-differentiated SH-SY5Y (SH-SY5YATRA) cells mimicking neuronal-like cells. After 3 h of incubation, the culture medium in the basal compartment was monitored for 13C enrichment by using elemental analysis isotope-ratio mass spectrometry (EA-IRMS) and effects on cell viability, plasma, and mitochondrial membrane potential. The neurotransmitter activation (BDNF, GABA, choline, and glutamate) of SH-SY5YATRA cells was also determined. Furthermore, these effects were also measured by the direct application of 13C-2´-FL and 13C-Fuc to SH-SY5YATRA cells. While no effects on neuronal-like cell activities were observed after intact 2´-FL or Fuc was incubated with SH-SY5YATRA cells, supernatants from the stat-growth phase of 2´-FL, fermented by B. longum ssp. infantis alone and together with B. breve, significantly induced BDNF release from SH-SY5YATRA cells. No such effects were found for 2´-FL, Fuc, or their fermentation products from B. breve. The BDNF release occurred from an enhanced vesicular release, which was confirmed by the use of the Ca2+-channel blocker verapamil. Concomitant with this event, 13C enrichment was also observed in the basal compartment when supernatants from the stat-growth phase of fermentation by B. longum ssp. infantis alone or together with B. breve were used. The results obtained in this study suggest that microbial products of 2´-FL rather than the oligosaccharide itself may influence neuronal cell activities.

Biomass conversion and radiocaesium (Rad-Cs) leaching behaviors of radioactive grass in anaerobic wet fermentation systems: Effects of pre-treatments

Persistent concerns regarding environmental hazards arise from the difficulty in disposing of radioactive plant-based wastes originating from the nuclear accident at the Fukushima Daiichi Nuclear Power Plant (FNPP) in Japan in 2011. In this study, three anaerobic digestion (AD) strategies were proposed: Sole anaerobic wet fermentation, and wet fermentations with either alkaline-heat or ultrasonic pre-treatment, which were employed for long-term anaerobic treatment of a genuine radioactive grass stemming from the FNPP accident. The objectives of this work are to investigate the effects of pre-treatments on biomass conversion efficiency and to gain insight into the leaching behavior of radiocaesium (Rad-Cs) within AD processes. Experimental results indicate that by introducing alkaline-heat and ultrasonic pre-treatments to AD systems, the removal efficiencies of total solids (TS) from the raw grass increased by 60.8 % and 42.5 %, respectively, compared to sole wet fermentation. Pre-treatments have been shown to enhance the stability of AD systems, both in terms of enhancing methane production and mitigating pH fluctuations triggered by the accumulation of organic acids. Remarkably, even though the Rad-Cs leaching rate was highest when the AD system was fed with the alkaline-heat pre-treated grass, it remained unsatisfactory at only 5.77 %. We inadvertently isolated a soil-like component from the raw grass, and analyzed both its proportion in the raw grass and the radioactivity intensity. The results indicate that although the soil constituted only 9.51 % TS of the raw grass, it accounted for a significant 81.35 % of the total radioactivity. The soil, which has a pronounced affinity for ionic Cs, being mixed into the raw grass, was identified as the primary factor limiting the leaching efficiency of Rad-Cs throughout both the pre-treatment and wet fermentation phases.

Dynamic changes in ferulic acid and diferulic acids in wheat flour doughs during the breadmaking process

Ferulic acid (FA), a phytochemical concentrated in wheat bran, influences structural characteristics of arabinoxylan (AX) and rheological properties of wheat dough. This study investigates the dynamic changes in FA and diferulic acids, closely associated with AX molecular weight, during the breadmaking process. FA predominantly exists in a tightly bound state within the arabinoxylan matrix, with a substantial increase in free FA content observed during the initial fermentation phase. Furthermore, this research identified four specific wheat-derived diferulic acids: 8–5′-DFA, 5–5′-DFA, 8-O-4′-DFA, and 8–5′-DFA (benzofuran form), tracking their variations throughout breadmaking. The notable upsurge in diferulic acid levels in the early fermentation stages suggests that the cleavage of ferulic acid moieties may not be the primary factor contributing to the reduction in AX molecular weight. Future investigations into the effects of FA and diferulic acids on arabinoxylan and wheat dough properties promise to enhance understanding of the intricacies of the breadmaking process.

Synergistic effects of lactobacillus strains and Acetobacter pasteurianus on jujube puree's product functionality and quality

Commercial lactic acid bacteria strains and indigenous Chinese acetic acid bacterium were co-cultivated bi- and tri-culturally in Junzao jujube puree for the first time to investigate their effects on physicochemical properties and quality attributes. Lactic-acetic acid bacteria co-fermentation was performed at 37 °C for 48 h during the anaerobic fermentation phase and at 30 °C for 144 h during aerobic fermentation. FTIR results showed that predominant wave numbers at 1716–1724 cm−1 and 2922–3307 cm−1 exhibited discernible alterations in the lactic-acetic acid co-fermented jujube purees compared to the control sample. Pearson correlation analysis showed that the flavonoid and flavonol contents were responsible for the enhanced 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) and 2,2-diphenyl-1-picrylhydrazyl scavenging activities of the fermented jujube purees. Consequently, fermented jujube puree from tricultures of Lactobacillus casei, Lactobacillus plantarum, and Acetobacter pasteurianus gave the best results, with the highest phenolics, flavonoid, and flavonol contents and the most improved antioxidative properties and color. Overall, lactic-acetic acid bacteria co-culture holds significant promise in valorizing Junzao jujube purees for functional ingredient development, paving the way for further research into similar interactions with different food matrices or microbial strains.

Predicting the multispecies solid-state vinegar fermentation process using single-cell Raman spectroscopy combined with machine learning

Microbial community is a key contributing factor for flavor formation in natural food fermentation. However, it is a challenge to maintain batch-to-batch uniformity during the fermentation process due to the diversity and variability of microbial community. A rapid detection of the structure and function of the microbial community in the whole fermentation process is of great importance for quality control of the final fermentation products. Firstly, we employed amplicon sequencing to target the dominant operational taxonomic units in the microbial community of Zhenjiang aromatic vinegar, a traditional cereal vinegar. Secondly, we isolated and created a Raman database for 13 dominant bacterial species from vinegar culture, enabling us to establish a logistic regression model with 96.4% accuracy in species classification. Finally, a Raman-fermentation phase regression model was established, achieving an R2 of 0.952, accurately determining the actual fermentation phase of vinegar. This study offers a new method for dynamics monitoring of microbial community, prediction of fermentation state, and decision of subsequent production operations in multi-species fermentation processes.

Integrating shotgun metagenomics and metabolomics to elucidate the dynamics of microbial communities and metabolites in fine flavor cocoa fermentation in Hainan

The aim of this study was to investigate the dynamic profile of microorganisms and metabolites in Hainan Trinitario cocoa during a six-day spontaneous box fermentation process. Shotgun metagenomic and metabolomic approaches were employed for this investigation. The potential metabolic functions of microorganisms in cocoa fermentation were revealed through a joint analysis of microbes, functional genes, and metabolites. During the anaerobic fermentation phase, Hanseniaspora emerged as the most prevalent yeast genus, implicated in pectin decomposition and potentially involved in glycolysis and starch and sucrose metabolism. Tatumella, possessing potential for pyruvate kinase, and Fructobacillus with a preference for fructose, constituted the primary bacteria during the pre-turning fermentation stage. Upon the introduction of oxygen into the fermentation mass, acetic acid bacteria ascended to dominant within the microflora. The exponential proliferation of Acetobacter resulted in a decline in taxonomic richness and abundance. Moreover, the identification of novel species within the Komagataeibacter genus suggests that Hainan cocoa may serve as a valuable reservoir for the discovery of unique cocoa fermentation bacteria. The KEGG annotation of metabolites and enzymes also highlighted the significant involvement of phenylalanine metabolism in cocoa fermentation. This research will offer a new perspective for the selection of starter strains and the formulation of mixed starter cultures.

Microbial metabolism during the thermophilic phase promotes the generation of aroma substances in nongxiangxing Daqu

The thermophilic phase of Daqu fermentation is considered the key period for aroma production in Daqu, but little is known about the changes in substances during this phase. In this study, we combined a metabolomics approach with high-throughput sequencing to analyze the metabolic profiles and identify metabolism-associated microbes during the thermophilic phase of Daqu fermentation. The results revealed that the metabolic sets after 5 and 9 days of fermentation in the thermophilic phase were similar, and several amino acid and biosynthesis-related metabolic pathways were significantly enriched. In addition, pyrazines and alkanes increased and esters decreased significantly after the thermophilic phase. The metabolism of substances during the thermophilic phase involved 38 genera, and the main metabolic pathways involved were glycolysis, TCA cycle, butyric acid metabolism, and five amino acid metabolic pathways. In summary, this study points in the direction for unravelling the mechanism of aroma production in Daqu.

Bacterial community and sensory quality from coffee are affected along fermentation under carbonic maceration

The diversity and activity of the indigenous microorganisms in coffee are essential for obtaining safe and good-quality coffee. The use of fermentation under carbonic maceration in coffee fruits showed a positive correlation between the bacterial community and sensory score. Thus, the objective of this study was to evaluate the bacterial diversity in coffee cherries during fermentation under carbonic maceration and their correlations with coffee-quality. Next-generation sequencing and Specialty Coffee Association protocol were used in this study. Predominance of Leuconostoc sp. and Lactobacillus sp. during fermentation was observed. Leuconostoc sp. had higher relative abundance in the initial phase of fermentation and at 18 and 28 °C than Lactobacillus sp. Furthermore, the greatest microbial diversity occurred at 38 °C and after 72 h. At this temperature, the relative abundance of Lactobacillus correlated positively with sensorial score. Thus, an increase in temperature and fermentation time favors Lactobacillus spp and coffee sensory quality.