Flavor formation through lactic acid bacteria metabolism in traditional Chinese fermented vegetable products

Lactic acid bacteria (LAB) have historically been used as starter cultures for the production of fermented foods, especially dairy products. Over recent years, new areas have had a strong impact on LAB studies: the application of omics tools; the study of complex microbial ecosystems, the discovery of new LAB species, and the use of LAB as powerhouses in the food and medical industries. This second edition of Biotechnology of Lactic Acid Bacteria: Novel Applications addresses the major advances in the fields over the last five years. Thoroughly revised and updated, the book includes new chapters. Among them: – The current status of LAB systematics; – The role of LAB in the human intestinal microbiome and the intestinal tract of animals and its impact on the health and disease state of the host; – The involvement of LAB in fruit and vegetable fermentations; – The production of nutraceuticals and aroma compounds by LAB; and – The formation of biofilms by LAB. This book is an essential reference for established researchers and scientists, clinical and advanced students, university professors and instructors, nutritionists and food technologists working on food microbiology, physiology and biotechnology of lactic acid bacteria.

Chapter 18 - Safety of Fermented Fruits and Vegetables

Nonstarter lactic acid bacteria volatilomes produced using cheese components

Traditional Chinese fermented foods are favored by consumers due to their unique flavor, texture and nutritional values. A large number of microorganisms participate in the process of fermentation, especially lactic acid bacteria (LAB), which are present in almost all fermented foods and contribute to flavor development. The formation process of flavor is complex and involves the biochemical conversion of various food components. It is very important to fully understand the conversion process to direct the flavor formation in foods. A comprehensive link between the LAB community and the flavor formation in traditional Chinese fermented foods is reviewed. The main mechanisms involved in the flavor formation dominated by LAB are carbohydrate metabolism, proteolysis and amino acid catabolism, and lipolysis and fatty acid metabolism. This review highlights some useful novel approaches for flavor enhancement, including the application of functional starter cultures and metabolic engineering, which may provide significant advances toward improving the flavor of fermented foods for a promising market.

Fermentation of various food stuffs by lactic acid bacteria (LAB) is one of the oldest forms of biopreservation practiced by mankind . Bacterial antagonism has been recognized for over a century but in recent years this phenomenon has received more scientific attention , particularly in the use of various strains of lactic acid bacteria One important attribute of many LAB is their ability to produce antimicrobial compounds called bacteriocins. In recent years interest in these compounds has grown substantially due to their potential usefulness as natural substitute for chemical food preservatives in the production of foods with enhanced shelf life and / or safety. There is growing consumer awareness of the link between diet and health. Recent scientific evidence supports the role of probiotic LAB in mediating many positive health effects.Traditional probiotic dairy strains of lactic acid bacteria have a long history of safe use and most strains are considered commensal microorganisms with no pathogenic potential.

Sichuan paocai, a microbial food predominantly fermented by lactic acid bacteria and hosting a complex and diverse microbial ecosystem, serves as an ideal habitat for bacteriophages. However, relatively few studies have been conducted on isolating bacteriophages from fermented vegetables and their application in vegetable fermentation. In this study, three staphylococcal bacteriophages, ΦSx-2, ΦSs-1, and ΦSs-2, were isolated and purified from Sichuan paocai using the spot test method. The morphological features of the phages were characterized using transmission electron microscopy (TEM), while key biological properties such as one-step growth kinetics were systematically evaluated, ultimately verifying their taxonomic placement within the Caudoviricetes class. Furthermore, the potential effects of these phages on the microbial community structure and physicochemical properties during paocai fermentation were investigated using high-throughput sequencing and standard physicochemical assays. Microbial community analysis demonstrated that introducing the phages significantly increased the relative abundance of lactic acid bacteria while reducing the prevalence of spoilage bacteria such as Erwinia, Pantoea, and Enterobacter. Physicochemical assessments revealed that adding phages accelerated the acidification process of paocai, effectively reduced nitrite levels, and increased the concentrations of lactic and acetic acids. Additionally, notable differences in color and flavor were observed between the two groups of paocai during the fermentation process. In summary, the inoculation of bacteriophages ΦSx-2, ΦSs-1, and ΦSs-2 optimized the microbial community structure, enhanced the fermentation process, and improved the quality of Sichuan paocai.

As the main dominant functional microorganism in the brewing process of Chinese Baijiu, lactic acid bacteria influences and determines the composition of microbial community structure, function, and enzyme profile in the Baijiu brewing process to a certain extent. Based on the important position and functional role of lactic acid bacteria in Chinese Baijiu and the progress of microbial analysis and detection technology, the research on lactic acid bacteria has become more and more in-depth in recent years. This paper reviews the research progress of lactic acid bacteria in the Chinese Baijiu brewing process in recent years, and e lactic acid bacteriaorates on the functional role and mechanism of lactic acid bacteria in Baijiu brewing process, aiming to provide theoretical reference for the research of lactic acid bacteria in Baijiu brewing process.

Unraveling the flavor formation mechanisms of Wanxi dry-cured goose: Microbiomics, metabolomics, and flavoromics study.

Lactic acid bacteria (LAB)-fermented vegetables might exhibit better functionalities than the raw vegetables themselves. LAB may prevent colon cancer by alteration of the metabolic activities of intestinal microflora, binding and degrading potential carcinogens, producing antimutagenic and antitumorigenic compounds, enhancing the host’s immune response, and other actions. The major groups of LAB identified by polymerase chain reaction in salt-fermented cucumber were Lactobacillus, Leuconostoc, and Pediococcus. LAB from dairy products exhibit various functionalities and have been used as probiotics; however, few bacteria from fermented vegetables other than kimchi LAB have been studied for possible functionalities. Vegetables fermented by LAB produce various fermented end products, flavors, and functional bioactive compounds. Kimchi LAB and kimchi have been studied for their health functionality along with assessments of increased shelf life and improved taste of the product. LAB can produce organic acids, including lactic acid, during vegetable fermentation.

The consumption of fermented vegetables is widespread throughout the world and represents an important component of the human diet with considerable contribution to the food supply for a world popula­tion in continuous growth. Many of the fermented vegetables share a general process which requires salting and acidification steps. Among the microorganisms responsible for fermentation, lactic acid bacteria are the most relevant with important organoleptic, quality and safety benefits. This review deals with the microbial ecology of fermented vegetables focusing on the biodiversity of lactic acid bacteria, the most important molecular tech­niques used for their identification and genotyping, their importance for the formation of biofilms as well as their use as starter cultures for obtaining high-quality and safe vegetable products.

PurposeFermented vegetables can be divided into two types, natural fermented and artificially inoculated fermented. By detecting and identifying the changes of bacterial diversity using physical and chemical indicators during natural and inoculation fermentation, we analyzed and determined the dominant bacteria in the fermentation process and revealed the relationship between bacteria and volatile substances.MethodsWe used the Illumina Miseq to sequence the bacteria in fermented vegetable samples at different fermentation periods, and calculated the total number of mesophilic microorganisms and lactic acid bacteria. We used the pH and nitrite to monitor the acidification process. GC-MS was used to determine volatile flavor compounds. Finally, we analyzed the correlation between volatile flavor compounds and bacteria.ResultsTotal mesophilic microorganisms and the number of lactic acid bacteria in the inoculated fermentation were higher than the natural fermentation. The bacterial diversity Shannon and Simpson indexes of the natural fermentation, higher than those of inoculated fermentation in 0~7 days, were between 55~71% and 36~45%, respectively. On the 7th day, the proportion of Lactobacillus in the natural fermentation and inoculated fermentation were 53.4% and 90.2%, respectively, which were significantly different. Lactobacillus was the dominant genus in the fermented vegetables and an important genus to promote the formation of volatile flavors. Lactobacillus was negatively correlated with two volatile substances (4-[2,2,6-trimethyl-7-oxabicyclo [4.1.0] hept-1-yl]-3-Buten-2-one (K4) and a-Phellandrene (X1)) and played a leading role in the fermentation process.ConclusionsResults demonstrated that the total number of mesophilic microorganisms and lactic acid bacteria in inoculated fermentation were more than those in natural fermentation. Inoculated fermentation can shorten the fermentation cycle and reduce the content of nitrite. Lactic acid bacteria were the dominant bacteria in fermented vegetables.

Unveiling the Secrets of Indonesian fermented Fish: Characteristics of lactic acid bacteria, roles, and potential in product development

The study evaluated the prebiotic potential of polyphenols from finger millet seed coat (FMSC) on lactic acid bacteria (LAB) and in turn the biotransformation of polyphenols by the action of probiotic bacteria. In vitro fermentation studies in terms of growth kinetics of LAB, prebiotic activity score (PAS), production of short chain fatty acids (SCFAs) and the changes in phenolic contents during fermentation were assessed by GC-MS and HPLC. FMSC polyphenols were efficiently utilized by the probiotic strains evident from the maximal growth rate in the logarithmic phase, among the strains, L. plantarum showed highest growth. A sharp drop in pH was recorded, a characteristic feature of LAB. SCFAs were produced in varying quantities. Phenolic monomers and aglycones appeared after probiotic fermentation. The study substantiates the bi-directional metabolism of FMSC polyphenols and LAB, which paves way for the development of functional foods that render potential health benefits to consumers.

Batch-dependent microbiota variation in mixed vegetable fermentations shapes the probiotic potential of autochthonous multifunctional cultures.

Cacao fermentation is a spontaneous process in which microorganisms play a key role in the development of distinctive chocolate flavors. The microbiota acting during cacao fermentation has been routinely characterized by culture-based techniques and next-generation sequencing using Illumina’s platform. However, the potential of in situ sequencing technologies to monitor microbial dynamics during cacao fermentation has not been assessed. In this study, cacao bean samples were collected at 0, 24, 48, 72, and 96 h after the start of the fermentation. Total DNA was extracted, and sequencing libraries were prepared for further sequencing using Illumina’s and Nanopore’s MinION sequencing platforms. Additionally, microorganisms were isolated using traditional culture-based methods. At the order and family taxonomic levels, Illumina and MinION sequencing revealed similar microbial composition in the samples. However, discrepancies were observed at the genus and species levels. In this sense, Illumina sequencing revealed a predominance of Limosilactobacillus, Levilactobacillus, Lactiplantibacillus, Frauteria, Saccharomyces and Acetobacter, while MinION sequencing showed a prevalence of Escherichia, Salmonella, Liquorilactobacillus, Lentilactobacillus, Acetobacter and Komagataeibacter during fermentation. The three methods were consistent in detecting the major yeast (Saccharomyces cerevisiae), lactic acid bacteria (Lactiplantibacillus plantarum, Leuconostoc pseudomesenteroides, Levilactobacillus brevis, Liquorilactobacillus mali, and Lentilactobacillus hilgardii) and acetic acid bacteria (Acetobacter pasteurianus) species during fermentation. Functional analysis based on a hybrid assembly of Illumina and MinION data revealed the roles of lactic acid bacteria and acetic acid bacteria in the metabolism of carbohydrates, amino acids, and secondary metabolites such as polyphenols and theobromine. This study represents the first report assessing the applicability of MinION sequencing for the characterization of microbial populations during cacao fermentation, demonstrating its potential as a complementary tool to established sequencing platforms.