Quality characteristics of high salt fermented fish sauce (budu) produced using autochthonous Virgibacillus halodenitrificans PS21 and Staphylococcus simulans PMRS35

Highlighting the Microbial Community of Kuflu Cheese, an Artisanal Turkish Mold-Ripened Variety, by High-Throughput Sequencing

Kuflu cheese, a popular variety of traditional Turkish mold-ripened cheeses, is characterized by its semi-hard texture and blue-green color. It is important to elucidate the microbiota of Kuflu cheese produced from raw milk to standardize and sustain its sensory properties. This study aimed to examine the bacteria, yeasts, and filamentous mold communities in Kuflu cheese using high-throughput amplicon sequencing based on 16S and ITS2 regions. Lactococcus, Streptococcus, and Staphylococcus were the most dominant bacterial genera while Bifidobacterium genus was found to be remarkably high in some Kuflu cheese samples. Penicillium genus dominated the filamentous mold biota while the yeasts with the highest relative abundances were detected as Debaryomyces, Pichia, and Candida. The genera Virgibacillus and Paraliobacillus, which were not previously reported for mold-ripened cheeses, were detected at high relative abundances in some Kuflu cheese samples. None of the genera that include important food pathogens like Salmonella, Campylobacter, Listeria were detected in the samples. This is the first experiment in which the microbiota of Kuflu cheeses were evaluated with a metagenomic approach. This study provided an opportunity to evaluate Kuflu cheese, which was previously examined for fungal composition, in terms of both pathogenic and beneficial bacteria.

The Contribution of Microorganisms to the Quality and Flavor Formation of Chinese Traditional Fermented Meat and Fish Products

Guizhou sour meat and sour fish, Chaoshan fish sauce, Sichuan sausage and bacon, Cantonese sausage, Jinhua ham, and Xinjiang air-dried beef are eight representatives of Chinese traditional fermented meat and fish products (FMFPs), which are favored by Chinese consumers due to their high nutritional value and quality. The quality of the spontaneously fermented Chinese traditional FMFP is closely correlated with microorganisms. Moreover, the dominant microorganisms are significantly different due to regional differences. The effects of microorganisms on the texture, color, flavor, nutrition, functional properties, and safety of Chinese traditional FMFPs have not been not fully described. Additionally, metabolic pathways for flavor formation of Chinese traditional FMFPs have not well been summarized. This article describes the seven characteristic Chinese traditional FMFPs and correlated dominant microorganisms in different regions of China. The effects of microorganisms on the texture, color, and flavor of Chinese traditional FMFPs are discussed. Furthermore, the metabolic pathways of microbial regulation of flavor formation in Chinese traditional FMFPs are proposed. This work provides a theoretical basis for improvement of Chinese traditional FMFPs by inoculating functional microorganisms isolated from Chinese traditional fermented foods.

Transforming the fermented fish landscape: Microbiota enable novel, safe, flavorful, and healthy products for modern consumers

Regular consumption of fish promotes sustainable health while reducing negative environmental impacts. Fermentation has long been used for preserving perishable foods, including fish. Fermented fish products are popular consumer foods of historical and cultural significance owing to their abundant essential nutrients and distinct flavor. This review discusses the recent scientific progress on fermented fish, especially the involved flavor formation processes, microbial metabolic activities, and interconnected biochemical pathways (e.g., enzymatic/non-enzymatic reactions associated with lipids, proteins, and their interactions). The multiple roles of fermentation in preservation of fish, development of desirable flavors, and production of health-promoting nutrients and bioactive substances are also discussed. Finally, prospects for further studies on fermented fish are proposed, including the need of monitoring microorganisms, along with the precise control of a fermentation process to transform the traditional fermented fish to novel, flavorful, healthy, and affordable products for modern consumers. Microbial-enabled innovative fermented fish products that consider both flavor and health benefits are expected to become a significant segment in global food markets. The integration of multi-omics technologies, biotechnology-based approaches (including synthetic biology and metabolic engineering) and sensory and consumer sciences, is crucial for technological innovations related to fermented fish. The findings of this review will provide guidance on future development of new or improved fermented fish products through regulating microbial metabolic processes and enzymatic activities.

Bacterial community structure, predicted metabolic activities, and formation of volatile compounds attributed to Malaysian fish sauce flavour

The fermentation of Malaysian fish sauce (budu) varies from one to twelve months depending on the producer, resulting in inconsistent quality. The microbiota, their predicted metabolic pathways and volatile metabolites profiles were determined at different stages of budu fermentation. Budu fermented for 1 and 3 months were characterized by the presence of Gram negative Enterobacterales, Gammaproteobacteria, and Fusobacteriaceae, which continuously decrease in abundance over fermentation time. The metabolic pathways prediction grouped 1- and 3- month budu in a cluster enriched with degradation reactions. 6-month budu were dominated by Halanaerobium and Staphylococcus, while the 12-month were dominated by Lentibacillus, Bacilli, and Halomonas. Biosynthesis-type predicted pathways involving protein and lipid derivatives were enriched in 6- and 12-month fermented budu, accumulating 2,6-dimethylpyrazine, methyl 2-ethyldecanoate, 2-phenylacetaldehyde, 3-methylbutanal, and 3-methylbutanoic acid. These compounds may indicate budu maturity and quality. This result may assist as a reference for quality control and fermentation monitoring.

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.

Histamine-degrading halophilic bacteria from traditional fish sauce: Characterization of Virgibacillus campisalis TT8.5 for histamine reduction

Traditionally produced fish sauce can contain significant amounts of histamine. In some instances, the histamine concentration may be well above the limit recommended by the Codex Alimentarius Commission. The aim of this study was to discover new bacterial strains capable of growing under the stressful environmental conditions of fish sauce fermentation and metabolizing histamine. In this study, 28 bacterial strains were isolated from Vietnamese fish sauce products based on their ability to grow at high salt concentrations (23% NaCl) and tested for their ability to degrade histamine. Strain TT8.5 showed the highest histamine-degradation (45.1 ± 0.2% of initially 5 mM histamine within 7 days) and was identified as Virgibacillus campisalis TT8.5. Its histamine-degrading activity was shown to be localized intracellularly and the enzyme is a putative histamine dehydrogenase. The strain exhibited optimal growth and histamine-degrading activity at 37°C, pH 7%, and 5% NaCl in halophilic archaea (HA) histamine broth. It also showed pronounced histamine-degrading activity in HA histamine broth when cultivated at temperatures of up to 40 °C as well as in the presence of up to 23% NaCl. After treatment with immobilized cells, 17.6-26.9% of the initial histamine in various fish sauce products were reduced within 24 h of incubation, while no significant changes in other parameters of fish sauce quality were observed after this treatment. Our results indicate that V. campisalis TT8.5 is of potential interest to be applied in histamine degradation of traditional fish sauce.