Next-generation sequencing reveals predominant bacterial communities during fermentation of Thai fish sauce in large manufacturing plants

Salt-Reduced Fish Sauce Produced under Pressurized Carbon Dioxide Treatment Using Sardinops melanostictus, Trachurus japonicus, Konosirus punctatus, Odontamblyopus lacepedii, Their Collective Mixture, and Unused Fish Mixture

Fish sauce is produced at high salt concentrations (>20%) to inhibit the growth of harmful microorganisms. The salt-reduced fish sauce (10% salt) was prepared under pressurized CO2 (pCO2) conditions at 30 °C and 5 MPa for 3 months (FSCO2), from Sardinops melanostictus, Odontamblyopus lacepedii, Trachurus japonicus, Konosirus punctatus, and their collective mixture, as well as unused fish mixture obtained from the Ariake Sea in Japan. FSCO2 exhibited significantly better microbial quality and free amino acid content, lighter color, standardized odor (dashi-like odor), and umami richness qualities compared to fish sauces prepared using the conventional method (FScon) (20% salt), as previously demonstrated, after a fermentation period of 2 months. Bacterial flora analysis implied that the standardization of odor and umami richness may not be the result of specific microbial metabolism. Even when using previously unused fish, it was possible to produce FSCO2 equivalent to that produced by conventional sardines and other fish. These results indicate that the quality of fish sauce can be improved. The flavor of FSCO2 became similar regardless of the type of fish and fermentation period using pCO2 during fermentation, leading to the effective utilization of unutilized fish as a resource for high-quality salt-reduced fish sauce.

Fermented Fish Products: Balancing Tradition and Innovation for Improved Quality

The flavor profile of fermented fish products is influenced by the complex interplay of microbial and enzymatic actions on the raw materials. This review summarizes the various factors contributing to the unique taste and aroma of these traditional foods. Key ingredients include locally sourced fish species and a variety of spices and seasonings that enhance flavor while serving as cultural markers. Starter cultures also play a critical role in standardizing quality and accelerating fermentation. Flavor compounds in fermented fish are primarily derived from the metabolism of carbohydrates, lipids, and proteins, producing a diverse array of free amino acids, peptides, and volatile compounds such as aldehydes, ketones, alcohols, and esters. The fermentation process can be shortened by certain methods to reduce production time and costs, allowing for faster product turnover and increased profitability in the fermented fish market. Fermented fish products also show potent beneficial effects. This review highlights the importance of integrating traditional practices with modern scientific approaches. Future research directions to enhance the quality of fermented fish products are suggested.

Exploring the Relationships Between Bacterial Community, Taste-Enhancing Peptides and Aroma in Thai Fermented Fish (Pla-ra)

As a traditional Thai condiment, Pla-ra is used to add flavor and richness to dishes. Nine treatment combinations of Pla-ra formulations created from 3 types of fish (Mor fish, Kradee fish, and Mor + Kradee fish) and 4 different carbohydrate sources (none, rice bran, roasted rice, and rice bran─roasted rice mixture) were studied through a 12 month fermentation period (1, 3, 5, 7, 8, 9, 10, 11, and 12 months). 16S rRNA Next Generation Sequencing (NGS) and LC-MS/MS techniques were used to analyze the microbial diversity and identify taste-enhancing peptides. Descriptive sensory analysis was performed on the extracts of the 108 Pla-ra samples mixed in a model broth. Koku perception and saltiness-enhancing attributes were clearly perceived and dominant in all samples, even though glutamyl peptides, including γ-Glu-Val-Gly, were found at subthreshold levels. The samples from mixed fish and Mor fish fermented with roasted ground rice and rice bran for 12 months had the most typical Pla-ra odors and tastes and had high taste-enhancing activities. NGS analysis revealed the presence of bacteria containing a large number of protease and aminopeptidase genes in the samples. Bacillus spp., Gallicola spp., and Proteiniclasticum spp. correlated well with the generation of glutamyl and arginyl peptides and typical odors in the samples. These results confirmed the typical sensory quality of Pla-ra depended on protein sources, carbohydrate sources, and bacteria communities. Further optimization of the microbial composition found could lead to the development of starter cultures to control and promote flavor development in fermented fish products.

Relationship between microorganisms and volatile components in each fermentation process in the kusaya gravy that plays an important role in the manufacturing of kusaya, a traditional Japanese fermented fish product

The relationship between the microbiota and volatile components of kusaya gravy involved in the manufacturing of kusaya, a traditional Japanese fermented fish product, in the Izu Islands (Niijima and Hachijojima) and the fermentation processes are not clear. In this study, we aimed to investigate the relationship between the microbiota and volatile compounds involved in the manufacturing and management of kusaya gravy. 16S ribosomal RNA (rRNA) gene-based amplicon sequencing revealed that the microbiota in kusaya gravy was significantly different between the two islands, and the microbiota hardly changed during each fermentation process. Gas chromatography-mass spectrometry analysis also revealed that the volatile components were strongly related to the microbiota in kusaya gravy, with Hachijojima samples containing sulfur-containing compounds and Niijima samples containing short-chain fatty acids. Therefore, our findings suggest that kusaya gravy is a characteristic fermented gravy with a stable microbiota, and the fermented pickling gravy is fermented by microorganisms.

Fermented fish and fermented fish-based products, an ever-growing source of microbial diversity: A literature review

Fermented fish and fermented fish-based products are part of the diet of many countries all over the world. Their popularity is not only due to the unique flavor, the distinct texture, and the good nutritional quality, but also to the easiness of the production process, that is commonly based on empirical traditional methods. Fish fermentation techniques ususally rely on the combination of some key steps, including salting, addition of spices or additives, and maintenance of anaerobic conditions, thus selecting for the multiplication of some pro-technological microorganisms. The objective of the present review was to provide an overview of the current knowledge of the microbial communities occurring in fermented fish and fish-based products. Specific information was collected from scientific publications published from 2000 to 2022 with the aim of generating a comprehensive database. The production of fermented fish and fish-based foods was mostly localized in West African countries, Northern European countries, and Southeast Asian countries. Based on the available literature, the microbial composition of fermented fish and fish-based products was delineated by using viable counting combined with identification of isolates, and culture-independent techniques. The data obtained from viable counting highlighted the occurrence of microbial groups usually associated with food fermentation, namely lactic acid bacteria, staphylococci, Bacillus spp., and yeasts. The identification of isolates combined with culture-independent methods showed that the fermentative process of fish-based products was generally guided by lactobacilli (Lactiplantibacillus plantarum, Latilactobacillus sakei, and Latilactobacillus curvatus) or Tetragenococcus spp. depending on the salt concentration. Among lactic acid bacteria populations, Lactococcus spp., Pediococcus spp., Leuconostoc spp., Weissella spp., Enterococcus spp., Streptococcus spp., and Vagococcus spp. were frequently identified. Staphylococcus spp. and Bacillus spp. confirmed a great adaptation to fermented fish-based products. Other noteworthy bacterial taxa included Micrococcus spp., Pseudomonas spp., Psychrobacter spp., Halanaerobium spp., and Halomonas spp. Among human pathogenic bacteria, the occurrence of Clostridium spp. and Vibrio spp. was documented. As for yeast populations, the predominance of Candida spp., Debaryomyces spp., and Saccharomyces spp. was evidenced. The present literature review could serve as comprehensive database for the scientific community, and as a reference for the food industry in order to formulate tailored starter or adjunctive cultures for product improvement.

Characterization of microbiota of naturally fermented sauerkraut by high-throughput sequencing

Sauerkraut is a traditionally fermented cabbage, with a unique taste and beneficial properties, in northeast China. The taste and flavor of sauerkraut vary from region to region, owing to the differences in microorganisms. Illumina MiSeq sequencing was used to identify and quantify the microbial community composition of the broth and leaves of the naturally fermented Suan-cai collected from northeast China. The alpha and beta diversity of the samples from three areas in Heilongjiang province shown that the complexity of bacterial diversity of the three samples was C, A and B in turn. The Lactobacillus widely existed in fermented sauerkraut, of these, Latilactobacillus sakei, Loigolactobacillus coryniformis subsp. torquens, Lactiplantibacillus plantarum subsp. plantarum, and Secundilactobacillus malefermentans were more abundant in the sauerkraut leaves than in fermentation broth. Other genera of lactic acid bacteria Pediococcus and Leuconostoc, which have potential probiotic properties, were also present. However, some harmful bacteria such as Arcobacter and Acinetobacter were also detected.

Factors affecting bacterial community dynamics and volatile metabolite profiles of Thai traditional salt fermented fish

Bacterial diversity of the Thai traditional salt fermented fish with roasted rice bran (Pla-ra) was investigated using classical and molecular approaches. Bacterial population of Pla-ra ranged from 10²-10⁶ in solid-state (SSF) and 10⁶-10⁹ CFU/g in submerged (SMF) fermentation types. Halanaerobium spp. and Lentibacillus spp. were the main genera particularly detected when rRNA analysis was applied. Tetragenococcus halophillus were dominant during the final stage in sea salt-recipe samples while Bacillus spp. were found in those rock salt recipes. In contrast, cultural plating demonstrated that Bacillus spp., generally B. amyloliquefaciens, were the dominant genera. In addition, B. pumilus, B. autrophaeus, B.subtilis and B. velezensis shown some relations with rock salt-recipe samples. The main volatile metabolites in all samples were butanoic acid and its derivatives. Key factors affected bacterial profiles and volatile compounds of salt fermented fish were type of salt, addition of roasted rice bran, and fermenting conditions.

Novel insight into flavor and quality formation in naturally fermented low-salt fish sauce based on microbial metabolism

Low-salt fermentation is an effective way to shorten the fermentation time of fish sauce. In this study, the changes of microbial community, flavor, and quality during the natural fermentation of low-salt fish sauce were studied, followed by the elucidation of flavor and quality formation mechanisms based on microbial metabolism. The 16S rRNA gene high-throughput sequencing showed that both richness and evenness of microbial community were reduced during fermentation. The microbial genera, including Pseudomonas, Achromobacter, Stenotrophomonas, Rhodococcus, Brucella, and Tetragenococcus were more suitable for the fermentation environment, and obviously increased along with the fermentation. There were a total of 125 volatile substances identified by HS-SPME-GC-MS, of which 30 substances were selected as the characteristic volatile flavor substances, mainly including aldehydes, esters, and alcohols. Large amounts of free amino acids were produced in the low-salt fish sauce, especially umami and sweet amino acids, as well as high concentrations of biogenic amines. Correlation network constructed by the Pearson's correlation coefficient showed that most characteristic volatile flavor substances were significantly positively correlated with Stenotrophomonas, Achromobacter, Rhodococcus, Tetragenococcus, and Brucella. Stenotrophomonas and Tetragenococcus were significantly positively correlated with most free amino acids, especially umami and sweet amino acids. Pseudomonas and Stenotrophomonas were positively correlated with most biogenic amines, especially histamine, tyramine, putrescine, and cadaverine. Metabolism pathways suggested that the high concentrations of precursor amino acids contributed to the production of biogenic amines. This study indicates that the spoilage microorganisms and biogenic amines in the low-salt fish sauce need to be further controlled, and the strains belonging to Tetragenococcus can be isolated as potential microbial starters for the production of low-salt fish sauce.

A Comprehensive Review with Future Insights on the Processing and Safety of Fermented Fish and the Associated Changes

As an easily spoiled source of valuable proteins and lipids, fish is preserved by fermentation in many cultures. Over time, diverse types of products have been produced from fish fermentation aside from whole fish, such as fermented fish paste and sauces. The consumption of fermented fish products has been shown to improve both physical and mental health due to the composition of the products. Fermented fish products can be dried prior to the fermentation process and include various additives to enhance the flavours and aid in fermentation. At the same time, the fermentation process and its conditions play a major role in determining the quality and safety of the product as the compositions change biochemically throughout fermentation. Additionally, the necessity of certain microorganisms and challenges in avoiding harmful microbes are reviewed to further optimise fermentation conditions in the future. Although several advanced technologies have emerged to produce better quality products and easier processes, the diversity of processes, ingredients, and products of fermented fish warrants further study, especially for the sake of the consumers' health and safety. In this review, the nutritional, microbial, and sensory characteristics of fermented fish are explored to better understand the health benefits along with the safety challenges introduced by fermented fish products. An exploratory approach of the published literature was conducted to achieve the purpose of this review using numerous books and online databases, including Google Scholar, Web of Science, Scopus, ScienceDirect, and PubMed Central, with the goal of obtaining, compiling, and reconstructing information on a variety of fundamental aspects of fish fermentation. This review explores significant information from all available library databases from 1950 to 2022. This review can assist food industries involved in fermented fish commercialization to efficiently ferment and produce better quality products by easing the fermentation process without risking the health and safety of consumers.

Dynamics of Bacterial Composition and Association with Quality Formation and Biogenic Amines Accumulation during Fish Sauce Spontaneous Fermentation

High-throughput sequencing and high-pressure liquid chromatography (HPLC) methods were used to investigate the influences of microbial dynamics on the quality and biogenic amine (BA) content during fish sauce fermentation. The homogeneity of total viable bacteria and lactic acid bacteria in fish sauce becomes higher as fermentation progresses. Tetragenococcus was the key genus of fish sauce fermentation. Carnobacterium (38.43%) and Lentibacillus (41.01%) were the dominant genera in the samples fermented for 3 months and 18 months, respectively. These three bacterial genera were significantly related to the physicochemical characteristics and characteristic flavors of the sauces. Tetragenococcus was significantly positively correlated with nitrogen oxides, the main characteristic flavor components in fish sauce. The BA content in fish sauce fermentation increased from 106.88 to 376.03 mg/kg, and the content of histamine reached 115.30 mg/kg at the end of fermentation, indicating that fish sauce has health risks. About 66.67% of Lentibacillus isolates were able to produce a large amount of BA, suggesting that Lentibacillus was the key genus for BA accumulation in fish sauce fermentation. Research on reducing the content of BA in fish sauce by intervening with regard to the fermentation temperature showed that a safe fish sauce product could be obtained at the fermentation temperature of about 25°C. These results help us to understand the contribution of microbial community composition to fish sauce fermentation and provide a basis for improving the quality and safety of fermented fish sauce. IMPORTANCE Traditional fermentation of fish sauce is mainly carried out by complex microbial communities from raw anchovies and processing environments. However, it is still unclear how the environmental microbiota influences the quality and the safety of fish sauce products. Therefore, this study comprehensively explained the influence of microorganisms on the quality and safety of fish sauce during the fermentation process in terms of physicochemical characters, flavors, and BA. Additionally, the accumulation of BA in fish sauce fermentation was controlled by intervening in the fermentation temperature. This finding contributes to a deeper understanding of the role of environmental microbiota during fermentation and provides data support for improving the safety of fish sauce.

Analysis of bacterial and fungal communities in fermented fish (pla-ra) from Northeast Thailand

Our aim was to explore the microbial community composition (bacteria and fungi) of fermented fish (pla-ra) from Northeast Thailand. We also made functional predictions concerning these microbial communities. The association between the microbiota and odor intensity was also analyzed. Fourteen samples of 1-year fermented fish samples derived from seven local markets in Khon Kaen, Northeast Thailand were used. The microbial community composition of each was investigated by sequencing the V1-V9 regions of the 16S rRNA gene (bacteria) and the ITS gene (fungi) using an Illumina MiSeq platform. Functional prediction analysis was conducted through Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) based on the use of the bacterial 16S rRNA gene sequences. The bacterial communities were rich, comprising 402 genera from 28 phyla, including such genera as Tetragenococcus, Staphylococcus, Virgibacillus, Lactobacillus and Lentibacillus. The fungal communities comprised 7 phyla and 60 genera, such as Heterobasidion, Densospora, Exophiala and Monascus. The bacterial community functional analysis revealed an association with six biological metabolic pathway categories (e.g., metabolism, genetic information processing, environmental information processing, cellular processes, organismal systems and human diseases) with 17 subfunctions, showing the richness of bacterial community functions. Odor-association analysis revealed that Brevibacterium, Brachybacterium and Chromohalobacter were more abundant in the weak-odor group, while Noviherbaspirillum was more abundant in the strong-odor group. This study provides a preliminary analysis of pla-ra microbial community structure and function in popular traditional Thai foods. Functional prediction analysis might be helpful to improve our knowledge of the microbiota in fermented fish.

Genome-Resolved Metaproteomic Analysis of Microbiota and Metabolic Pathways Involved in Taste Formation During Chinese Traditional Fish Sauce (Yu-lu) Fermentation

Complex microbial metabolism is key to taste formation in high-quality fish sauce during fermentation. To guide quality supervision and targeted regulation, we analyzed the function of microbial flora during fermentation based on a previously developed metagenomic database. The abundance of most identified genes involved in metabolic functions showed an upward trend in abundance during fermentation. In total, 571 proteins extracted from fish sauce at different fermentation stages were identified. These proteins were mainly derived from Halanaerobium, Psychrobacter, Photobacterium, and Tetragenococcus. Functional annotation revealed 15 pathways related to amino acid metabolism, including alanine, aspartate, glutamate, and histidine metabolism; lysine degradation; and arginine biosynthesis. This study demonstrated the approaches to identify microbiota functions and metabolic pathways, thereby providing a theoretical basis for taste formation mechanisms during traditional fish sauce fermentation.

Regulation of microbial metabolism on the formation of characteristic flavor and quality formation in the traditional fish sauce during fermentation: a review

Fish sauce is a special flavored condiment formed by traditional fermentation of low-value fish in coastal areas, which are consumed and produced in many parts of the world, especially in Southeast Asia. In the process of fish sauce fermentation, the diversity of microbial flora and the complex metabolic reactions of microorganisms, especially lipid oxidation, carbohydrate fermentation and protein degradation, are accompanied by the formation of flavor substances. However, the precise reaction of microorganisms during the fersmentation process is difficult to accurately control in modern industrial production, which leads to the loss of traditional characteristic flavors in fermented fish sauces. This paper reviews the manufacturing processes, core microorganisms, metabolic characteristics and flavor formation mechanisms of fermented fish sauces at home and abroad. Various methods have been utilized to analyze and characterize the composition and function of microorganisms. Additionally, the potential safety issues of fermented fish sauces and their health benefits are also reviewed. Furthermore, some future directions and prospects of fermented fish sauces are also reviewed in this paper. By comprehensive understanding of this review, it is expected to address the challenges in the modern production of fish sauce thereby expanding its application in food or diet.

Physicochemical characteristics and flavor profiles of fermented fish sauce (budu) during fermentation in commercial manufacturing plant

This study was done by dynamically monitoring the changes in bacterial composition, physicochemical characteristics, and volatile substances during fermentation of fermented fish sauce (budu). The degree of hydrolysis, TCA-soluble peptides, and nitrogen contents increased as the fermentation time progressed. A continuous decrease in peroxide value and thiobarbituric acid reactive substances was noted over 60 days of fermentation. A total of 44 volatile compounds were detected, and increases in volatile compounds, such as 2-methylbutanal, 3-methylbutanal, benzaldehyde, and 2-ethyl furan, with low odor thresholds values, might contribute to budu's flavor of the final product. Additionally, the relationship between evolving microbiota and the formation of flavor compounds was analyzed, and halophilic lactic acid bacteria was identified to be the most important bacterial contributing to flavor and aroma development. This finding will provide important information for improving the quality of budu in terms of flavor characteristics.

Beyond Archaea: The Table Salt Bacteriome

Commercial table salt is a condiment with food preservative properties by decreasing water activity and increasing osmotic pressure. Salt is also a source of halophilic bacteria and archaea. In the present research, the diversity of halotolerant and halophilic microorganisms was studied in six commercial table salts by culture-dependent and culture-independent techniques. Three table salts were obtained from marine origins: Atlantic Ocean, Mediterranean (Ibiza Island), and Odiel marshes (supermarket marine salt). Other salts supplemented with mineral and nutritional ingredients were also used: Himalayan pink, Hawaiian black, and one with dried vegetables known as Viking salt. The results of 16S rRNA gene sequencing reveal that the salts from marine origins display a similar archaeal taxonomy, but with significant variations among genera. Archaeal taxa Halorubrum, Halobacterium, Hallobellus, Natronomonas, Haloplanus, Halonotius, Halomarina, and Haloarcula were prevalent in those three marine salts. Furthermore, the most abundant archaeal genera present in all salts were Natronomonas, Halolamina, Halonotius, Halapricum, Halobacterium, Haloarcula, and uncultured Halobacterales. Sulfitobacter sp. was the most frequent bacteria, represented almost in all salts. Other genera such as Bacillus, Enterococcus, and Flavobacterium were the most frequent taxa in the Viking, Himalayan pink, and black salts, respectively. Interestingly, the genus Salinibacter was detected only in marine-originated salts. A collection of 76 halotolerant and halophilic bacterial and haloarchaeal species was set by culturing on different media with a broad range of salinity and nutrient composition. Comparing the results of 16S rRNA gene metataxonomic and culturomics revealed that culturable bacteria Acinetobacter, Aquibacillus, Bacillus, Brevundimonas, Fictibacillus, Gracilibacillus, Halobacillus, Micrococcus, Oceanobacillus, Salibacterium, Salinibacter, Terribacillus, Thalassobacillus, and also Archaea Haloarcula, Halobacterium, and Halorubrum were identified at least in one sample by both methods. Our results show that salts from marine origins are dominated by Archaea, whereas salts from other sources or salt supplemented with ingredients are dominated by bacteria.

Comparison of the microbial community and flavor compounds in fermented mandarin fish (Siniperca chuatsi): Three typical types of Chinese fermented mandarin fish products

Fermented mandarin fish have been receiving attention from consumers due to their nutritional value and specific flavor. Microbial diversity in fermented mandarin fish has an important impact on their flavor and quality. However, little is known about the microbiome and the differences among different products. In this study, the bacterial profiles and flavor compounds in three typical fermented mandarin fish products were investigated and compared, and a correlation network was used to explore the potential relationship between microorganisms and flavor. Bacterial community analysis demonstrated clear differences in microbiota among the HF-, MF-, and OF-fermented mandarin fish products. Psychrilyobacter, Fusobacterium, and Vibrio were the most dominant in the HF-, MF-, and OF-fermented products, respectively. In addition, 14, 12, and 4 flavor substances (relative odor activity value, ROAV ≥ 1) were detected in the muscles from the central dorsal and ventral sides of the three samples, respectively. Several bacteria correlated with the production of important flavor compounds, and three genera (Arcobacter, Psychrilyobacter, and Shewanella) were the primary microorganisms contributing to more than six characteristic flavor compounds in fermented mandarin fish products. Therefore, the study's systematic method allows identificating important microbes and characteristic volatile flavor compounds in fermented mandarin fish and provides new insights into the relationship between microorganisms and flavor.

Determination of microbial diversities and aroma characteristics of Beitang shrimp paste

Beitang shrimp paste (BSP) is fermented by different parts of shrimp, such as the head (H), meat (M), or the whole shrimp (S and W). Microbial communities of BSP were dominated by Firmicutes and Proteobacteria at the phyla level and Tetragenococcus at the genus level. However, the microbial diversity of M was the lowest than the others. Non-dominant bacterial communities were presented by a mutual symbiotic model in BSP fermentation. Tetragenococcus, Halanaerobium, Streptococcus, and Brevundimonas were positively correlated with the biosynthesis of amino acids, fatty acids, and metabolic cofactors; Marinilactibacillus and Pseudomonas might be the main contributors to inorganic sulfides, nitrogen oxides, and long-chain alkanes in BSP; Psychrobacter was closely related to the ester characteristics of methyl palmitoleate and methyl hexadecanoate in H. Halanaerobium and Streptococcus promoted the production of pyrazines in S. Tetragenococcus was positively correlated with acetic acid, decanoic acid, and palmitic acid that improved the sour aroma of M. The relationship between bacteria and aroma formation under different raw materials was expected to improve the quality of BSP.

Investigation of Kokumi Substances and Bacteria in Thai Fermented Freshwater Fish (Pla-ra)

A 16S rRNA next-generation sequencing technique was applied to investigate the microbial diversity and liquid chromatography-tandem mass spectrometry was used to identify glutamyl peptide profiles of 10 Thai fermented freshwater fish (Pla-ra) samples. A total of 12 genera of bacteria were able to be detected, with Tetragenococcus spp., Staphylococcus spp., and Lactobacillus spp. dominating. Of the 18 glutamyl peptides analyzed, 17 were found, even though the amounts detected were lower than the taste threshold. Despite this, an increase in mouthfulness sensation, reflecting kokumi activity, was clearly identified in most of the samples, which might be because of a synergistic effect of different sub-threshold compounds present in the samples. In principle component analysis, the relationship between microorganisms and glutamyl peptide generation was observed, especially between Tetragenococcus spp. and Lentibacillus spp. and the generation of γ-Glu-Val-Gly. Correlations between microbial diversity and the generation of taste enhancers were identified in this study.

Unraveling the Microbiota of Natural Black cv. Kalamata Fermented Olives through 16S and ITS Metataxonomic Analysis

Kalamata natural black olives are one of the most economically important Greek varieties. The microbial ecology of table olives is highly influenced by the co-existence of bacteria and yeasts/fungi, as well as the physicochemical parameters throughout the fermentation. Therefore, the aim of this study was the identification of bacterial and yeast/fungal microbiota of both olives and brines obtained from 29 cv. Kalamata olive samples industrially fermented in the two main producing geographical regions of Greece, namely Aitoloakarnania and Messinia/Lakonia. The potential microbial biogeography association between certain taxa and geographical area was also assessed. The dominant bacterial family identified in olive and brine samples from both regions was Lactobacillaceae, presenting, however, higher average abundances in the samples from Aitoloakarnania compared to Messinia/Lakonia. At the genus level, Lactobacillus, Celerinatantimonas, Propionibacterium and Pseudomonas were the most abundant. In addition, the yeasts/fungal communities were less diverse compared to those of bacteria, with Pichiaceae being the dominant family and Pichia, Ogataea, and Saccharomyces being the most abundant genera. To the best of our knowledge, this is the first report on the microbiota of both olives and brines of cv. Kalamata black olives fermented on an industrial scale between two geographical regions of Greece using metagenomics analysis.

Novel insight into the formation mechanism of volatile flavor in Chinese fish sauce (Yu-lu) based on molecular sensory and metagenomics analyses

Complex microbial metabolism is the basis for flavor formation in traditional fish sauce. To guide the targeted regulation of production quality, we used molecular sensory and metagenomics analyses to determine dynamic changes in volatile flavor compounds and microbial communities of fish sauce as fermentation progressed. In total, 56 volatile compounds were identified; of these, 3-methylthiopropanal had the highest average odor activity value. Twelve volatile compounds, key for fish sauce flavor development, were identified. Bidirectional orthogonal partial least squares analysis was applied to investigate the correlation between microorganisms and flavor substances. Five microbial genera including Halanaerobium, Halomonas, Tetragenococcus, Halococcus and Candidatus Frackibacter constituted the core microbial flora responsible for flavor formation. The microbial metabolic pathways degraded raw materials into primary metabolites, such as glucose, amino acids, and fatty acids. This study provides novel insights into the flavor formation mechanism of traditional fish sauce fermentation.