Lactic Fermentation Research Articles

Effect of Exogenous Inoculation on Dark Fermentation of Food Waste Priorly Stored in Lactic Acid Fermentation

Lactic acid fermentation has recently been shown to be a robust storage strategy for food waste prior to conversion to biohydrogen through dark fermentation. However, the importance of initial microbial communities and, more particularly, exogenous microorganisms on the conversion of lactic acid-rich stored substrate is not yet fully elucidated. This study investigates the impact of introducing exogenous inoculum to lactic acid-rich stored food waste prior to biohydrogen production in dark fermentation. Results showed exogenous inoculation produced a statistically significant increase in biohydrogen production rate (Rm) by 199%, 250%, 137%, 130%, 19%, and 10% compared to non-inoculated stored food waste after food waste storage at 4 °C, 10 °C, 23 °C, 35 °C, 45 °C, and 55 °C, respectively. Interestingly, no impact on the maximum production yield (Pm) was observed, but exogenous inoculation increased the accumulation of acetate, up to 160% more compared to endogenous inoculum. The main hydrogen-producing bacteria (HPB) were affiliated with Clostridium sp., while Prevotella_9 sp., another known HPB, was found after the fermentation of the food waste stored at 23 °C. In this study, the interest of exogenous inoculation to convert food waste stored by lactic acid fermentation was demonstrated through an increase in production rate along with higher accumulation of co-products, e.g., acetate. Such findings are promising for further development of process coupling, combining storage and conversion by fermentation of complex food waste.

The systemic evolutionary theory of the origin of cancer (SETOC): an update

The Systemic Evolutionary Theory of the Origin of Cancer (SETOC) is a recently proposed theory founded on two primary principles: the cooperative and endosymbiotic process of cell evolution as described by Lynn Margulis, and the integration of complex systems operating in eukaryotic cells, which is a core concept in systems biology. The SETOC proposes that malignant transformation occurs when cells undergo a continuous adaptation process in response to long-term injuries, leading to tissue remodeling, chronic inflammation, fibrosis, and ultimately cancer. This process involves a maladaptive response, wherein the 'endosymbiotic contract’ between the nuclear-cytoplasmic system (derived from the primordial archaeal cell) and the mitochondrial system (derived from the primordial α-proteobacterium) gradually breaks down. This ultimately leads to uncoordinated behaviors and functions in transformed cells. The decoupling of the two cellular subsystems causes transformed cells to acquire phenotypic characteristics analogous to those of unicellular organisms, as well as certain biological features of embryonic development that are normally suppressed. These adaptive changes enable cancer cells to survive in the harsh tumor microenvironment characterized by low oxygen concentrations, inadequate nutrients, increased catabolic waste, and increased acidity. De-endosymbiosis reprograms the sequential metabolic functions of glycolysis, the TCA cycle, and oxidative phosphorylation (OxPhos). This leads to increased lactate fermentation (Warburg effect), respiratory chain dysfunction, and TCA cycle reversal. Here, we present an updated version of the SETOC that incorporates the fundamental principles outlined by this theory and integrates the epistemological approach used to develop it.

Isolamento e seleção de bactérias lácticas produtoras de ácido γ-aminobutírico e aplicação na fermentação de suco de tomate enriquecido com GABA

ABSTRACT: Tomatoes (Solanum lycopersicum L.) are nutrient-rich fruits with a high glutamic acid content, making them a suitable source for producing γ-aminobutyric acid (GABA) through the action of lactic acid bacteria (LAB). LAB plays a pivotal role in lactic fermentation, enhancing the taste and nutritional value of food products, often contributing to their health benefits. This study isolated GABA-producing LAB from tomatoes and assessed their potential for producing GABA-enriched fermented tomato juice. The results indicated the isolation of 15 LAB strains from the samples of five different tomatoes. All of these strains demonstrated the capability to produce GABA, with levels ranging from 1.732 to 3.113 mg/mL, as determined using thin-layer chromatography (TLC). Through sequencing, the promising strain TO42, identified as Weissella cibaria, was selected for tomato juice fermentation. Furthermore, GABA-enriched tomato juice was successfully fermented at 15 °Brix for 72 h, resulting in the highest recorded GABA and lactic acid content of 9.185 ± 0.398 mg/mL and 13.05 ± 1.56 g/L, respectively.

Effects of liquid state vs. solid state lactic fermentation on drying, nutritional composition, phytochemical profile, and in vitro neuro-related bioactivities of Cheungsam industrial hempseed (Korean breed)

Effects of liquid state vs. solid state lactic fermentation on drying, nutritional composition, phytochemical profile, and in vitro neuro-related bioactivities of Cheungsam industrial hempseed (Korean breed)

Effects of Lactic Acid Bacteria Fermentation and In Vitro Simulated Digestion on the Bioactivities of Purple Sweet Potato Juice.

The effects of lactic acid bacteria fermentation and in vitro simulated digestion on phenolic bioavailability, phenolic bioavailability, and antioxidant activity of purple sweet potato juice (PSPJ) were investigated. The PSPJ was fermented by Lactobacillus rhamnosus and Streptococcus thermophilus. The viable bacterial count, phenolic components, antioxidant activity, phenolic bioaccessibility, and phenolic bioavailability of PSPJ were analyzed during the simulated digestion process in vitro. The data displayed that lactic acid bacteria fermentation increased total α-glucosidase inhibition, total flavonoid content, and ratephenolic content. The antioxidant activities were improved after in vitro simulated digestion due to the biotransformation of phenolic substances by lactic acid bacteria fermentation. The bioaccessibility and bioavailability of phenols in PSPJ were improved with fermentation of lactic acid bacteria. Furthermore, the viable bacteria count of the two strains was significantly improved (>7 log CFU/mL) after simulated digestion in vitro.

Evaluation of a Novel Potentially Probiotic/Pediococcus acidilactici ORE5 in Lactic Acid Fermentation of Cornelian Cherry Juice: Assessment of Nutritional Properties, Physicochemical Characteristics, and Sensory Attributes

The present research survey aimed to investigate the effect of a novel, potentially probiotic strain Pediococcus acidilactici ORE5 on the fermentation of Cornelian cherry for 24 h at 30 °C, followed by cold storage for 4 weeks. Two fermentation systems were established, differing in the form of P. acidilactici ORE5 applied as starter culture of (i) free cells and (ii) immobilized cells in delignified wheat bran. A high lactic acid fermentation rate was recorded, especially in the case of immobilized cell application, since lactic acid levels were determined at 184.8 mg/100 mL and acetic acid at 12.7 mg/100 mL. High probiotic load was observed throughout all studied periods, even at the fourth week of cold storage for both fermentation systems (above 8 log cfu/mL). The total phenolics content (TPC) of the fermented juices was high elevated compared to the unfermented one in all studied periods. When immobilized cells were applied, the TPC of the fermented juice attained the highest values (224.4.5–285.1 mg GAE/100 mL) compared to the juice fermented with free cells (204.5–258.4 mg GAE/100 mL) and the unfermented juice (140.5–165.8 mg GAE/100 mL). Improvements in the sensorial features of the fermented juice compared to the unfermented were also recorded during cold storage. Overall, the results of the present research demonstrated that P. acidilactici ORE5 can be successfully applied in lactic acid fermentation of Cornelian cherry juice, leading to a functional product with increased nutritional value, high probiotic load, and improved sensorial features.

Yeast microflora of dairy products sold in Russia

Using restriction analysis of the 5.8S-ITS rDNA fragment and sequencing of the D1/D2 domain of 26S rDNA, the yeast microflora of various dairy products sold in Russia was studied. Most of the fermented milk products studied were dominated by lactose-utilizing yeasts Kluyveromyces and Debaryomyces, as well as lactose-negative yeasts Saccharomyces, Monosporozyma, Pichia, Geotrichum and Yarrowia. The yeast Kluyveromyces marxianus was present in most of the fermented milk products studied, while the related species K. lactis was found only in some samples of ayran, curds and cheese. The dominance of K. marxianus is apparently associated with their physiological characteristics (thermo- and osmotolerance), which provide these yeasts with better adaptation to industrial fermentation conditions. The dominant species in mixed-fermentation dairy products, Saccharomyces cerevisiae and Monosporozyma unispora, were completely absent in cheeses and lactic acid fermentation products. In general, the species composition of yeasts largely depended on the fermented milk product, the type of milk and the specific manufacturer.

Modulation of adzuki (Vigna angularis) bean milk analog substrates and metabolites through singular and/or combined treatment of germination and lactic acid fermentation.

Given the growing interest in dairy-free milk analog products, new and diversified alternatives are pivotal to push the market forward. Germination and fermentation are traditional processing technologies used in plant-based milk production. However, the combination of both has not been extensively investigated. The aim of this study was to investigate the potential combined beneficial effects of coupling germination and fermentation on selected substrates and metabolites in adzuki bean milk analog. It was found that germination increased essential amino acids to 1193.44 from 421.46mg/L in control while raising simple sugar and "green" (green odor) volatile compounds. Fermentation with probiotic Limosilactobacillus fermentum enriched the adzuki bean milk analog with probiotics and organic acids, whereby it also reduced some free amino acids (especially arginine) and "green" volatiles. Germination coupled with fermentation was able to overcome the deficiencies of the respective single treatment by elevating essential amino acid content (with a 4.8-fold increase in lysine and a 3.8-fold increase in histidine) and removing "green" odor volatiles while biofortifying the bean milk with probiotics, organic acids, and vitamin (nicotinic acid). Overall, a combination of germination and fermentation merits further research for substrate and metabolite modulation to develop novel and nutritious plant-based milk analogs with desirable flavor.

Effects of Lactic Acid Bacterial Fermentation on the Biochemical Properties and Antimicrobial Activity of Hemp Seeds

Recently, there has been an increase in the application of lactic acid bacteria (LAB) for seed fermentation because of the improved functional, technological, and nutritional properties of the fermented seeds. The purpose of this study was to evaluate the effects of selected LAB on the biochemical and antimicrobial features of fermented hemp seeds and their water-, salt-, and ethanol-soluble protein fractions. The results showed that hemp seed medium was suitable for Lactiplantibacillus plantarum, Levilactobacillus brevis, and Lactobacillus acidophilus multiplication (with a LAB count > 109 colony-forming units/g). The biochemical and antimicrobial properties of the fermented hemp seeds strictly depended on the LAB strain used for fermentation. The hemp seeds fermented with L. brevis, which was previously isolated from rye sourdough, presented the highest total phenolic content and phytase, amylase, protease, and antioxidant activities. The hemp seeds fermented with L. acidophilus showed the broadest spectrum of antimicrobial activity against foodborne pathogens. The ethanol-soluble protein fractions from the fermented hemp seeds inhibited the growth of Escherichia coli, Staphylococcus aureus, Salmonella typhimurium, Bacillus subtilis, and Bacillus cereus, while the ethanol-soluble protein fraction from unfermented hemp seeds did not have an antimicrobial effect. The results of ABTS·+ radical scavenging and antimicrobial activity assays by agar well diffusion method confirmed that the tested LAB strains for hemp seed fermentation influenced the antioxidant and antimicrobial activities of protein fractions.

Mineral Bioaccessibility of Pistachio-Based Beverages: the Effect of Lactic Acid Bacteria Fermentation.

The aim of this work was to study the effects of two LAB strains on the bioaccessibility (BA) of minerals after the fermentation of pistachio-based beverages. The beverages were made with two varieties of pistachio (Argentina, AP and Italian, IP). Aliquots were inoculated with 106 CFU of two different LAB strains and fermented for 24h at 28°C. Six types of beverages were obtained: two controls (AP-c and IP-c), two fermented with LAB1 (AP-f1 and IP-f2) and two fermented with LAB2 (AP-f2 and IP-f2). The contents of minerals, phytic acid, and ascorbic acid were evaluated. To determine the BA of minerals, the samples were subjected to a simulated gastrointestinal digestion with equilibrium dialysis in the intestinal stage. The IP presented higher contents of Ca and Fe than the AP ones. The ascorbic acid content was higher for AP than for IP, and increased in both beverages after fermentation, obtaining a 70% increase in IP-f1. Phytic acid content was higher for AP than for IP, and decreased after fermentation to a greater extent when fermented with LAB1 (50% reduction). In all the cases, mineral BA was higher in fermented samples, being BA values dependent on the pistachio variety and the LAB strain. Negative correlations (p < 0.05) were observed between the BA of Ca and Mg with phytic acid content. The fermentation of the pistachio beverages with LAB allowed increasing the BA of minerals, improving the nutritional quality of the pistachio-based beverage.

A Novel Non-Alcoholic Einkorn-Based Beverage Produced by Lactic Acid Fermentation: Microbiological, Chemical, and Sensory Assessment.

Einkorn (Triticum monococcum L. ssp. monococcum) is gaining renewed interest for its high nutritional value and digestibility. Lactic acid fermentation could enhance these properties by improving micronutrient bioavailability, sensory properties, and shelf life. This study aimed to develop a novel non-alcoholic einkorn-based beverage through lactic acid fermentation. A multiple-strain starter was selected based on acidifying properties and inoculated into an einkorn-based substrate to produce a yogurt-like beverage. Prototypes were evaluated through physico-chemical, chemical, and microbiological analyses and compared to uninoculated controls. A sensory analysis was also performed to assess flavor attributes before and after lactic acid fermentation. The inoculated starter culture reached a load of approximately 9 Log CFU g⁻¹ and remained viable throughout storage, leading to an increase in lactic acid concentration and high titratable acidity, corresponding to low pH values. Total polyphenol content increased during fermentation and remained stable during storage, whereas antioxidant activity did not show significant differences over time. An increase in monosaccharides, acids, and ketones was observed during fermentation and storage. The prototypes exhibited a distinctive proximate composition, along with yogurt and fruity aroma notes. These results suggest the feasibility of producing a safe and stable non-alcoholic einkorn-based fermented beverage with appealing sensory characteristics.

Enhancing iron and zinc bioavailability in maize (Zea mays) through phytate reduction: the impact of fermentation alone and in combination with soaking and germination.

Phytates are nutrient-binding compounds found mainly in cereals and legumes, which may significantly contribute to micronutrient malnutrition in regions where phytate-rich cereals, such as maize, are staple food. This study investigated how maize fermentation, both alone and in combination with soaking and germination, can reduce phytate levels and enhance the estimated bioavailability of iron and zinc. We evaluated various fermentation methods, including spontaneous fermentation; fermentation with starter cultures, either Lactiplantibacillus plantarum 299v® (Lp299) or yogurt containing viable Lacticaseibacillus casei; and fermentation with Lp299 of soaked and germinated maize. The outcome variables included changes in pH and lactic acid content during fermentation, and measurements of phytate levels (spectrophotometry), minerals (Atomic absorption) and protein (protein analyzer) in maize samples before and after treatments. Fermentation with Lp299 of soaked and germinated maize grains yielded a phytate reduction of up to 85.6% decreasing from 9.58 ± 0.05 g·kg-1 in raw maize to 1.39 ± 0.09 g·kg-1 after processing. Fermentation of raw maize flour using Lp299 or yogurt resulted in a similar phytate reduction of 65.3% (3.35 ± 0.26 g·kg-1) and 68.7% (3.02 ± 0.01 g·kg-1) respectively. Spontaneous fermentation yielded a phytate reduction of 51.8% (4.65 ± 0.40 g·kg-1). This reduction in phytate content enhanced the estimated bioavailability of iron and zinc, particularly in the soaking-germination-fermentation combination, where the Phytate:Zinc molar ratio (Phy:Zn) dropped from 40.76 to 7.77, representing 81% reduction from the raw maize. The Phytate:Iron molar ratio (Phy:Fe) dropped from 41.42 to 6.24 indicating an 85% reduction. Additionally, fermentation led to a significant increase (p = 0.001) in protein content in maize flour after fermentation, ranging from 7.3 to 10.3% after the various fermentation treatments. There was not significant difference in the protein increase when compared the fermentation types. Lactic acid fermentation of soaked and germinated maize grains, emerged as the most promising process to enhance the bioavailability of essential minerals. This approach could help alleviate mineral deficiencies in populations dependent on maize-based diets. The findings underscore the potential of fermentation to be applied at the household level, which may bring up an alternative for programs and policies focused on reducing micronutrient deficiencies and improving food security in developing regions.

Interaction between human dental microbiome and the host gingival model

Objective: Interactions between the dental biofilm and host are important to study infectious oral diseases such as dental caries and periodontitis. Previous studies have reported the reaction of a host gingival model co-cultured with bacteria or biofilms. However, these studies only report results of a gingival model, and a biofilm co-cultured with a gingival model has never been investigated although the microbiome of dental biofilms is associated with maintenance of health and onset of infectious oral diseases. Therefore, we aimed to investigate the reaction of a gingival model and experimental biofilm. An in situ dental biofilm model, which enables biofilm formation in the oral cavity, was used to prepare experimental biofilms. Methods: The in situ biofilm was co-cultured with a reconstructed gingival model (RHG). We performed 16S rRNA sequence analysis, metagenomic function prediction analysis, total bacterial cell counts using quantitative polymerase chain reaction, and confocal laser microscopic observation in addition to gene expression and histological investigation of RHG. Results: We found a change in Veillonella abundance in the in situ biofilms co-cultured with RHG. Metagenomic function prediction analysis revealed that the activity of certain pathways associated with amino acid production, lactic acid fermentation, and glycolysis system significantly increased in biofilms co-cultured with RHG. Conclusion: The microbiome and functions of dental biofilms can be affected by host gingival tissues. Our findings will contribute to the establishment of a host–biofilm interaction model to understand the pathophysiology of oral infectious diseases.

Impact of lactic acid bacterial fermentation on the chemical composition, antioxidant capacities and flavor properties of dandelion

Dandelion is a medicinal and food plant with a long history of medicinal use, but its application as a functional food has been limited. In this study, the fermentation characteristics of four lactic acid bacteria (LAB) in dandelion were investigated and aimed to screen out the LAB that can improve the nutrition and flavor of dandelion. The results showed that all strains grew well, with L. plantarum having the lowest pH and highest total acidity after fermentation. Fermented dandelions (FDs) showed significantly higher total phenolic and flavonoid contents. The antioxidant and hypoglycaemic activities were also enhanced. Lactic and tartaric acids contents increased significantly after fermentation. The three characteristic phenolic acids were differently changed by different LAB strains. L. plantarum-FD had the highest content of chlorogenic acid (17.22 mg/g), and L. casei-FD had the highest content of caffeic and chicoric acids (0.77 mg/g and 14.90 mg/g, respectively). LAB improved the herbal flavor of dandelion by reducing alcohols, increasing acids and altering the concentrations of other volatiles. Aldehydes and esters increased more in the L. plantarum- and L. fermentum-FDs than in the other groups. L. fermentum added pyrazines in particular but also produced unpleasant butanoic acid and methylpyrazine. Overall, L. plantarum fermentation has shown great potential in improving the flavor and enhancing the biological functions of dandelion. It will be beneficial for enriching dandelion products and increasing added value.

Study on the Mechanisms of Flavor Compound Changes During the Lactic Fermentation Process of Peach and Apricot Mixed Juice.

This study employed headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) and liquid chromatography-mass spectrometry (LC-MS) for non-targeted metabolomics analyses to examine the impact of mixed fermentation with various lactic acid bacteria (LAB) on the flavor compounds and metabolites of peach and apricot mixed juice (PAMJ), specifically focusing on the alterations of volatile compounds and non-volatile metabolites, as well as their metabolic pathways during the fermentation process. A total of 185 volatiles were identified using HS-SPME-GC-MS analysis, revealing significant differential metabolites, including eugenol, benzaldehyde, and γ-decalactone etc. The results indicated that lactic fermentation significantly enhanced the overall flavor of the juice toward the end of the fermentation process. In the interim, untargeted metabolomics utilizing LC-MS identified 1846 divergent metabolites, with 564 exhibiting up-regulation and 1282 demonstrating down-regulation. The metabolic pathway study performed by the Kyoto Encyclopedia of Genes and Genomes (KEGG) revealed significant changes in the metabolic levels of amino acids and saccharides after the lactic fermentation of PAMJ. Primarily associated with amino acid metabolism and starch and sucrose metabolism pathways. This work establishes a theoretical foundation for advancing fermented fruit juices with superior quality.

Lactiplantibacillus plantarum KABP051: Stability in Fruit Juices and Production of Bioactive Compounds During Their Fermentation.

The lactic fermentation of fruit and vegetable juices by well-characterised probiotics remains relatively underexplored. We have investigated the stability and impact of Lactiplantibacillus plantarum KABP051 fermentation on orange, apple, and peach juices by microbiological, physicochemical, and sensory evaluation means. For each fruit juice, three different samples were analysed: original fruit juice without probiotic as blank (B), fruit juice inoculated with 107 CFU/mL of probiotic without fermentation (P), and fruit juice inoculated with 107 CFU/mL of probiotic and fermented at 37 °C for 24 h (PF). P samples displayed good stability throughout the study, and PF samples showed an initial increase in CFUs accompanied by a change in pH, confirming the ability of the probiotic to ferment these juices. After 60 days of refrigeration, PF samples contained >107 CFU/mL. Total phenolic content and antioxidant capacity were equivalent in F, P, and PF. Remarkably, deep metabolomic analyses confirmed malolactic fermentation and revealed the production of several bioactive compounds including the antimicrobial substance phenyllactic acid, the immunomodulatory and anti-fatigue amino acid N-acetyl glutamine, the vitamin B3 form nicotinic acid, the monoterpene (-)-β-pinene, and the neurotransmitter acetylcholine, among others, during probiotic fermentation. Finally, a hedonic analysis involving 51 participants showed that probiotic fermented orange juice is well accepted by panellists, with scores comparable to those of the control juice. Overall, we here show that fruit juices are excellent carriers for the delivery of the probiotic L. plantarum KABP051 and its non-alcoholic fermentation can result in tasty functional fruit juices enriched with health-promoting compounds.

Using process modeling and simulation to determine the sustainability of a novel lactic acid biorefinery in Europe: Influence of process improvements, scale, energy source, and market conditions

The biorefinery concept aims to produce multiple high-value products from bio-based feedstocks. One such product is lactic acid, which is used across several industries such as food, pharmaceuticals, cosmetics, and chemicals. Lactic acid yield is influenced by several factors, and improvements in performance are often first demonstrated at lab-scale, requiring prospective models which make assumptions about how the system will be optimized to understand the potential of a commercial-scale plant. This study assesses the economic and environmental sustainability of a proposed lactic acid biorefinery through the combination of process modelling, techno-economic assessment, and life cycle assessment. The case study proposes producing high purity lactic acid from industrial candy waste and liquid digestate in Denmark through lactic acid fermentation and downstream membrane separations. A base case is first modelled to determine the economic and environmental hotspots of the system; scenarios are then modelled where improvement methods are implemented reducing consumption of energy, chemicals, water, and the production of waste, upscaling the system, and integrating bioenergy. Finally, a cost sensitivity analysis is run varying bioenergy, water, chemical, and labor costs based on the European market. By optimizing unit processes, scale, energy sources and market conditions, the lactic acid unit production cost and global warming potential can be lowered by 94% and 80% compared to the base case, respectively. However, these are optimized in different scenarios, indicating a trade-off in optimizing economic and environmental criteria. As even best-case lactic acid unit production cost is found to be 141–232% higher than market price, this production pathway will require further improvement or market changes before it can be commercially viable.

The Effect of Ultrasound and Lactic Acid Fermentation on the Selected Quality Parameters and Bioactive Compounds Content in Fermented Pumpkin (Cucurbita pepo L.).

Increasing the consumption of fruit and vegetables can be achieved by creating new products. A promising method seems to be the directed fermentation of vegetables. The aim of this study was to investigate the effect of ultrasonic pretreatment (US; 25 kHz; 5 min) and the lactic acid bacteria strain (LAB; Lactiplantibacillus plantarum 299v and Lacticaseibacillus rhamnosus GG) on the quality of fermented pumpkin (Cucurbita pepo L.). The pumpkin was inoculated with 5 log CFU/g of specific LAB strain. Fermentation was carried out for 7 days at 35 °C. Some samples were US treated at the washing stage. During fermentation, there was an increase in the LAB count of 3 logarithmic cycles compared to the initial inoculum. For L. rhamnosus, preceding fermentation by US treatment contributed to an increased bacteria count of 4 logarithmic cycles. In the case of fermentation with L. rhamnosus, the lactic acid content was significantly higher than for L. plantarum. These samples are also characterized by higher sensory properties, desirability of taste, and overall desirability. Fermentation contributed to a decrease in carotenoid and phenolic compounds content and an increase in the antioxidant capacity of the pumpkins, regardless of the bacterial strain.

Changes of volatile flavored compounds during lactic acid fermentation in cereal-based products

Lactic acid bacteria (LAB)-mediated fermentation of cereals is a preservation technique that enhances food flavor, nutrition, and safety. LAB naturally exists in cereals and plays a significant role in fermentation converting sugars into lactic acid and lowering the pH levels to create a distinctive sour taste and aroma. This process increases nutritional value and produces compounds like ethanol, acetic acid, and carbon dioxide, contributing to texture and appearance. LAB fermentation breaks down complex carbohydrates and proteins, improving digestibility and nutrient absorption. Common LAB-fermented cereal-based foods include sourdough bread, fermented cereal porridges, yogurt and kefir. Effective monitoring of volatile flavor compounds during fermentation is crucial for ensuring the quality, safety, and consumer acceptance of these foods. Keywords: Cereal-based food, Volatile flavor compounds, Lactic acid bacteria, Fermentation, Amino acid metabolism, HPLC, GC-MS

Metabolomic and proteomic profiling reveals the formation mechanism of volatile flavor in egg whites during fermentation by Streptococcus thermophilus

In this study, the flavor of egg whites was significantly improved by lactic acid fermentation, and the metabolic networks of metabolites, volatile compounds, and enzymes were established using gas chromatography–mass spectrometry, metabolomic, and proteomic. Results indicate that among ten types of common lactic acid bacteria, Streptococcus thermophilus endowed egg white with the most pleasant flavor through increasing aldehydes, ketones, alcohols, esters, terpenoids, and aromatic compounds. Amino acid catabolism was the predominant pathway for generating most aldehydes, alcohols, acids, and esters. The changes in the organic acids and derivatives (mainly amino acids, peptides, and analogues) concentration during fermentation are attributed to the hydrolysis of egg white proteins by proteinases and peptidases, and the regulation of enzymes involved in amino acid biosynthesis and other reactions. This study provides a valuable reference for future investigations focusing on regulating the flavor release of egg whites.